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  • The grapevine NaE sodium exclusion locus encodes sodium transporters with diverse transport properties and localisation
    J. Plant Physiol. (IF 2.825) Pub Date : 2020-01-17
    Yue Wu; Sam W Henderson; Stefanie Wege; Fei Zheng; Amanda R Walker; Rob R Walker; Matthew Gilliham
    更新日期:2020-01-17
  • Aluminium triggers oxidative stress and antioxidant response in the microalgae Scenedesmus sp
    J. Plant Physiol. (IF 2.825) Pub Date : 2020-01-15
    Maryam Ameri; Angel Baron-Sola; Ramazan Ali Khavari-Nejad; Neda Soltani; Farzaneh Najafi; Abdolreza Bagheri; Flor Martinez; Luis E. Hernández

    Aluminium (Al) water pollution is an increasing environmental problem and comprehensive analysis of toxic responses of aquatic primary producer organisms is imperative. We characterized the antioxidant response of Scenedesmus sp. microalga to Al-induced oxidative stress. After 72 h of exposure to Al (0, 10, and 100 µM) in a modified Bold Basal Medium (pH 5.0), we observed cell aggregation and alterations in the subcellular structure, strong lipid peroxidation and oxidative stress induction (detected with the fluorescent probe 2',7'-dichlorodihydrofluorescein diacetate) in parallel with Al accumulation in cells. At the same time, Al toxicity caused depletion of important macronutrients like Ca, which is important for cell-wall structure. Analysis of antioxidant enzymatic activities in Al-treated Scenedesmus cells revealed that catalase, ascorbate peroxidase, as well as different isoforms of superoxide dismutase were inhibited especially at the highest Al dose (100 µM), cells that accumulated the highest concentration of Al. On the other hand, glutathione reductase activity increased at that Al concentration. Immunodetection after Western-blotting confirmed that only ascorbate peroxidase inhibition was apparently due to a decrease in enzyme levels. However, the inhibition of catalase and activation of glutathione reductase activities seemed related with post-translational modifications in protein function as protein expression decreased or increased, respectively under Al stress. Our results may help to understand toxic mechanisms triggered by Al in freshwater microalgae, which in turn could aid to select suitable biomarkers of Al contamination in aquatic ecosystems.

    更新日期:2020-01-15
  • Radial water transport in arbuscular mycorrhizal maize plants under drought stress conditions is affected by indole-acetic acid (IAA) application
    J. Plant Physiol. (IF 2.825) Pub Date : 2020-01-15
    Gabriela Quiroga; Gorka Erice; Ricardo Aroca; Ángel María Zamarreño; José María García-Mina; Juan Manuel Ruiz-Lozano

    Drought stress is one of the most devastating abiotic stresses, compromising crop growth, reproductive success and yield. The arbuscular mycorrhizal (AM) symbiosis has been demonstrated to be beneficial in helping the plant to bear with water deficit. In plants, development and stress responses are largely regulated by a complex hormonal crosstalk. Auxins play significant roles in plant growth and development, in responses to different abiotic stresses or in the establishment and functioning of the AM symbiosis. Despite these important functions, the role of indole-3acetic acid (IAA) as a regulator of root water transport and stress response is not well understood. In this study, the effect of exogenous application of IAA on the regulation of root radial water transport in AM plants was analyzed under well-watered and drought stress conditions. Exogenous IAA application affected root hydraulic parameters, mainly osmotic root hydraulic conductivity (Lo), which was decreased in both AM and non-AM plants under water deficit conditions. Under drought, the relative apoplastic water flow was differentially regulated by IAA application in non-AM and AM plants. The effect of IAA on the internal cell component of root water conductivity suggests that aquaporins are involved in the IAA-dependent inhibition of this water pathway.

    更新日期:2020-01-15
  • DNA methylation of LDOX gene contributes to the floral colour variegation in peach
    J. Plant Physiol. (IF 2.825) Pub Date : 2020-01-15
    Xinxin Wu; Yong Zhou; Dan Yao; Shahid Iqbal; Zhihong Gao; Zhen Zhang

    Peach is an important fruit and ornamental plant around the globe. Variegation in flowers often captures consumers’ attention, and variegated plants are of high ornamental value. To determine the relationship between DNA methylation and phenotype, we obtained the first single-nucleotide resolution DNA methylation of variegation cultivars in peach through bisulfite sequencing. In this study, a similar methylation rate of 12.90% in variegated flower buds (VF) and 11.96% in red flower buds (RF) was determined. The methyl-CG (mCG) was the main context in both samples. We identified 503 differentially methylated regions (DMRs) in all chromosomes. These DMRs were focused on 96 genes and 156 promoters. Associated with the transcriptional and proteome analysis, 106 differently expressed genes and 52 different proteins had varying degrees of methylation. Silent genes exhibited higher methylation levels than expressed genes. The methylation state of the leucoanthocyanidin dioxygenase (LDOX) promoter in VF was higher than RF at flower stages 2 (FS2) based on bisulfite sequencing PCR (BSP) results. Moreover, further experiments showed LDOX gene expression and enzyme activity in RF was higher than VF. The DNA methylation trend consisted of the gene expression and flower colour phenotype. Several cis-acting regulatory elements on BSP sequences were involved in phytohormones, transcription factors, and light responsiveness, which could affect gene expression. The higher level of LDOX gene expression promoted synthesis of colourful anthocyanidins, which caused red spots on the petal. Together, this study identified the context and level of methylation at each site with bisulfite sequencing (BS). These results are helpful in uncovering the mechanism of variegated flower petal formation in peach.

    更新日期:2020-01-15
  • The cytosolic protein GRP1 facilitates abscisic acid- and darkness-induced stomatal closure in Salvia miltiorrhiza
    J. Plant Physiol. (IF 2.825) Pub Date : 2020-01-07
    Yuanchu Liu; Wen Ma; Wen Zhou; Lin Li; Donghao Wang; Bin Li; Shiqiang Wang; Yiqin Pan; Yaping Yan; Zhezhi Wang

    By screening an expressed sequence tag (EST) library of Salvia miltiorrhiza, we detected an acidic protein, SmGRP1, with no significant similarities to the other sequences in public databases. SmGRP1 encodes a peptide of 151 amino acids, 33.77% of which are glutamic acid residues, and the peptide was positive according to “stains-all” staining. Expression analysis revealed that SmGRP1 was expressed in all examined tissues of S. miltiorrhiza but was most highly expressed in the leaves and stems. Without a signal peptide, SmGRP1 localized to the cytoplasm in protoplasts in subcellular localization experiments. SmGRP1 expression was prominently enhanced by ABA and darkness treatments; the protein could also be induced by high temperature, NaCl, and dehydration treatments, while low temperature suppressed its expression. Furthermore, although there were no obvious phenotypic differences in SmGRP1 overexpression and SmGRP1 knockdown mutants compared with control plants under normal culture conditions, the stomata of the knockdown lines remained open when treated with ABA, darkness, NO, and H2O2. In addition, the water loss rate of the knockdown mutants was faster than that of the control lines and overexpression mutants when exposed to air. These observations indicate that SmGRP1 is a novel acidic protein with potential calcium-binding capability and is involved in stomatal movement and stress resistance.

    更新日期:2020-01-07
  • Alternative polyadenylation of the stacyose synthase gene mediates source-sink regulation in cucumber
    J. Plant Physiol. (IF 2.825) Pub Date : 2020-01-02
    Jinji Zhang; Hao Gu; Haibo Dai; Zhiping Zhang; Minmin Miao

    Alternative polyadenylation (APA) is a pervasive mechanism for gene regulation in eukaryotes. Stachyose is the main assimilate translocated in the cucumber phloem. Stachyose synthase (CsSTS) catalyzes the last step of stachyose biosynthesis in cucumber leaves and plays a key role in the regulation of assimilate partitioning between source and sink. In this study, three CsSTS mRNAs with the same open reading frame and the 5`untranslated region (UTR), but differing in their 3`UTRs, named CsSTS1 (short), CsSTS2 (medium), and CsSTS3 (long), were identified. Southern blot and sequence analysis of the cucumber genome confirmed that these transcripts are regulated through APA from a single gene. No significant difference of in vitro translation efficiency was found among three mRNAs. However, the relative stabilities of three transcripts varied among different tissues and different leaf development stages of cucumber. CsSTS1 expression in cucumber calli was up-regulated by the raffinose (substrate of CsSTS) and down-regulated by stachyose (product of CsSTS), respectively. In cucumber plants, all three isoforms have considerable expression in non-fruit node leaves. However, in fruit-carrying node leaves, the expression of CsSTS2 and CsSTS3 was severely inhibited and only CsSTS1 was highly expressed, indicating fruit setting has a remarkable effect on the relative expression level of three transcripts. This “fruit setting” effect could be observed until at least 36 h after the fruit was removed from the node. Our results suggest that abundant expression of CsSTS1 is beneficial for stachyose loading in source leaves, and APA is a delicate mechanism for CsSTS to regulate cucumber source-sink balance.

    更新日期:2020-01-02
  • H2O2 Accumulation, Host Cell Death and Differential Accumulation of Proteins Related to Photosynthesis and Redox Homeostasis Required for Viral Replication: Explaining the Resistance of EMS-mutagenized Cowpea to Cowpea Severe Mosaic Virus
    J. Plant Physiol. (IF 2.825) Pub Date : 2019-12-28
    Pedro Filho Noronha Souza; Jose Tadeu Abreu Oliveira; Ilka Maria Vasconcelos; Vladimir Gonçalves Magalhães; Fredy Davi Albuquerque Silva; Rodolpho Glauber Guedes Silva; Kleber Sousa Oliveira; Octavio Luis Franco; Joaquim Albenisio Gomes Silveira; Fabricio Eulalio Leite Carvalho

    Infection with Cowpea severe mosaic virus (CPSMV) represents one of the main limitations for cowpea (Vigna unguiculata L. Walp.) productivity due to the severity of the disease symptoms, frequency of incidence, and difficulties in dissemination control. This study aimed to identify the proteins and metabolic pathways associated with the susceptibility and resistance of cowpea plants to CPSMV. Therefore, we treated the seeds of a naturally susceptible cowpea genotype (CE-31) with the mutagenic agent ethyl methane sulfonate (EMS) and compared the secondary leaf proteomic profile of the mutagenized resistant plants inoculated with CPSMV (MCPI plant group) to those of the naturally susceptible cowpea genotype CE-31 inoculated (CPI) and noninoculated (CPU) with CPSMV. MCPI responded to CPSMV by accumulating proteins involved in the oxidative burst, increasing H2O2 generation, promoting leaf cell death (LCD), increasing the synthesis of defense proteins, and decreasing host factors important for the establishment of CPSMV infection. In contrast, CPI accumulated several host factors that favor CPSMV infection and did not accumulate H2O2 or present LCD, which allowed CPSMV replication and systemic dissemination. Based on these results, we propose that the differential abundance of defense proteins and proteins involved in the oxidative burst, LCD, and the decrease in cowpea protein factors required for CPSMV replication are associated with the resistance trait acquired by the MCPI plant group.

    更新日期:2019-12-29
  • Stomatal traits as a determinant of superior salinity tolerance in wild barley
    J. Plant Physiol. (IF 2.825) Pub Date : 2019-12-28
    Ali Kiani-Pouya; Fatemeh Rasouli; Barkat Rabbi; Zhinous Falakboland; Miing Yong; Zhong-Hua Chen; Meixue Zhou; Sergey Shabala

    Wild barley Hordeum spontaneum (WB) is the progenitor of a cultivated barley Hordeum vulgare (CB). Understanding efficient mechanisms evolved by WB to cope with abiotic stresses may open prospects of transferring these promising traits to the high yielding CB genotypes. This study aimed to investigate the strategies that WB plants utilise in regard to the control of stomatal operation and ionic homeostasis to deal with salinity stress, one of the major threats to the global food security. Twenty-six genotypes of WB and CB were grown under glasshouse conditions and exposed to 300 mM NaCl salinity treatment for 5 weeks followed by their comprehensive physiological assessment. WB had higher relative biomass than CB when exposed to salinity stress. Under saline conditions, WB plants were able to keep constant stomatal density (SD) while SD significantly decreased in CB. The higher SD in WB also resulted in a higher stomatal conductance (gs) under saline conditions, with gs reduction being 51% and 72% in WB and CB, respectively. Furthermore, WB showed faster stomatal response to light, indicating their better ability to adapt to changing environmental conditions. Experiments with isolated epidermal strips indicated that CB genotypes have the higher stomatal aperture when incubated in 80 mM KCl solution, and its aperture declined when KCl was substituted by NaCl. On the contrary, WB genotype had the highest stomatal aperture being exposed to 80 mM NaCl suggesting that WB plants may use Na+ instead of K+ for stomata movements. Overall, our data suggest that CB employ a stress-escaping strategy by reducing stomata density, to conserve water, when grown under salinity conditions. WB, on a contrary, is capable of maintaining relatively constant stomata density, faster stomatal movement and higher gs under saline conditions.

    更新日期:2019-12-29
  • OsERdj7 is an ER-resident J-protein involved in ER quality control in rice endosperm
    J. Plant Physiol. (IF 2.825) Pub Date : 2019-12-24
    Masaru Ohta; Fumio Takaiwa

    OsERdj7 is one of six endoplasmic reticulum (ER)-resident J-domain-containing proteins (J-proteins) encoded by the rice genome that acts as a co-chaperone for Hsp70 and is characterized by the presence of two transmembrane domains. It is N-glycosylated and primarily exists in a dimeric form with a molecular mass of 64 kDa. When the microsomal fraction of maturing seeds was treated with alkaline, high salt or detergent compounds, OsERdj7 was solubilized, even in alkaline and high salt environments, indicating that it is not tightly integrated in the ER membrane. Next, to investigate its role during seed maturation, expression of OsERdj7 was specifically downregulated using RNA interference (RNAi) under the control of the endosperm-specific 16 kDa prolamin promoter in transgenic rice. As a result, the unfolded protein response (UPR) was induced in maturing seeds via activation of OsIRE1/OsbZIP50 and ATF6 orthologs, such as OsbZIP39 and OsbZIP60, leading to upregulation of several chaperones and folding enzymes. Furthermore, some prolamins (RM4 and RM9) were retained in the ER lumen in the form of a mesh-like structure without deposition to the inherent ER-derived protein bodies (PB-Is), although major storage protein glutelins were normally transported to protein storage vacuoles (PB-IIs). On the other hand, induction of ER associated degradation (ERAD) increased OsERdj7 expression in transgenic rice seeds in which ERAD related genes were highly expressed. Due to PDIL2-3 and OsHard3 co-immunoprecipitating with OsERdj7 in rice protoplasts, this result implicates OsERdj7 in the translocation of some seed proteins within the ER lumen and in the degradation of misfolded or unfolded proteins.

    更新日期:2019-12-25
  • CIP elicitors on the defense response of A. macrocephala and its related gene expression analysis
    J. Plant Physiol. (IF 2.825) Pub Date : 2019-12-20
    Peifeng Zhang; Fang Zheng; Lei Chen; Xiaofang Lu; Wei Tian

    Plant-derived elicitor is a new type of plant vaccine developed in the contemporary era, and it has safe and broad application prospects in organic agriculture. Research on defense mechanisms triggered by elicitor has become a hot topic in recent years. The Chrysanthemum indicum polysaccharide (CIP) obtained by separation and purification from Chrysanthemum indicum was used as an elicitor in this work. This elicitor has been shown to be effective in Atractylodes macrocephala Koidz (A. macrocephala) against Sclerotium rolfsii sacc (S. rolfsii) infection and soil-borne diseases. However, the mechanism of induced disease resistance has not been elucidated. In this research, we study the CIP-induced A. macrocephala defense response from the level of signal molecules and the defensive enzyme gene expression. Several defense responses to CIP treatment have been found in A. macrocephala, including early hydrogen peroxide (H2O2) production, accumulation of salicylic acid (SA) and increased phytoalexin (PA) content. In addition, CIP significantly increased the activity of related defense enzymes in A. macrocephala. RT-qPCR analysis showed that defense-related genes such as polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) were up-regulated after CIP treatment. To obtain the sequence of the defense enzyme gene, we are the first to provide a public and comprehensive A. macrocephala database by transcriptome sequencing. These results together demonstrate that CIP triggers defense responses in A. macrocephala. Our research not only provides further research on immune mechanism between plant and elicitor, but also sheds new light on strategy for biocontrol in the future.

    更新日期:2019-12-20
  • Inhibitors of tri- and tetra- polyamine oxidation, but not diamine oxidation, impair the initial stages of wound-induced suberization
    J. Plant Physiol. (IF 2.825) Pub Date : 2019-12-17
    Edward C. Lulai; Linda L. Olso; Karen K. Fugate; Jonathan D. Neubauer; Larry G. Campbell

    The mechanisms regulating, and modulating potato wound-healing processes are of great importance in reducing tuber infections, reducing shrinkage and maintaining quality and nutritional value for growers and consumers. Wound-induced changes in tuber polyamine metabolism have been linked to the modulation of wound healing (WH) and in possibly providing the crucial amount of H2O2 required for suberization processes. In this investigation we determined the effect of inhibition of specific steps within the pathway of polyamine metabolism on polyamine content and the initial accumulation of suberin polyphenolics (SPP) during WH. The accumulation of SPP represents a critical part of the beginning or inchoate phase of tuber WH during closing-layer formation because it serves as a barrier to bacterial infection and is a requisite for the accumulation of suberin polyaliphatics which provide the barrier to fungal infection. Results showed that the inhibitor treatments that caused changes in polyamine content generally did not influence wound-induced accumulation of SPP. Such lack of correlation was found for inhibitors involved in metabolism and oxidation of putrescine (arginine decarboxylase, ornithine decarboxylase, and diamine oxidase). However, accumulation of SPP was dramatically reduced by treatment with guazatine, a potent inhibitor of polyamine oxidase (PAO), and methylglyoxal-bis(guanylhydrazone), a putative inhibitor of S-adenosylmethione decarboxylase which may also cross-react to inhibit PAO. The mode of action of these inhibitors is presumed to be blockage of essential H2O2 production within the WH cell wall. These results are of great importance in understanding the mechanisms modulating WH and ultimately controlling related infections and associated postharvest losses.

    更新日期:2019-12-18
  • Biosynthesis pathway of indole-3-acetyl-myo-inositol during development of maize (Zea mays L.) seeds
    J. Plant Physiol. (IF 2.825) Pub Date : 2019-12-16
    Maciej Ostrowski; Anna Ciarkowska; Agata Dalka; Emilia Wilmowicz; Anna Jakubowska

    Indole-3-acetic acid (IAA) conjugation is one of the mechanisms responsible for auxin homeostasis. IAA ester conjugates biosynthesis has been studied during development of maize seeds where IAA-inositol (IAInos) and its glycosidic forms make up about 50% of its ester conjugates pool. 1-O-indole-3-acetyl-β-D-glucose (IAGlc) synthase and indole-3-acetyl transferase (IAInos synthase) are key enzymes in a two-step pathway of IAInos synthesis. In the first reaction, IAA is glucosylated to a high energy acetal, 1-O-indole-3-acetyl-β-D-glucose by IAGlc synthase, whereas in the second step, IAInos synthase transfers IAA moiety to myo-inositol forming a stable auxin ester, indole-3-acetyl-myo-inositol (IAInos). It should be mentioned that IAGlc synthase catalyzes a reversible reaction with unfavourable equilibrium that delivers IAGlc for favourable transacylation to IAInos. This is the first study where IAGlc synthase and IAInos synthase are simultaneously analyzed by enzymatic activity assay and quantitative RT-PCR in maize seeds at four stages of development (13, 26, 39 and 52 Days After Flowering). Activity of IAGlc/IAInos synthases as well as their expression profiles during seed development were different. While both enzymatic activities and ZmIAIn expression were the highest in seeds at 26 DAF, the highest expression of ZmIAGlc was observed at 13 DAF. Protein gel blot analysis showed that IAInos synthase exists as a mixture of several isoforms at a similar protein level at particular stages of seed development. Neither of other ester conjugates of IAA (IAA-mannose) nor IAA-amino acids were detected at the stages studied. Catalytic activity of L-tryptophan aminotransferase involved in IAA biosynthesis as well as UDPG pyrophosphorylase, synthesizing UDPG as a substrate for IAGlc synthase, were also analyzed. L-tryptophan aminotransferase activity was the highest at 26 DAF. Changes in enzyme activity of UDPG pyrophosphorylase are difficult to interpret. Expression levels of ZmIPS and ZmIPP encoding two enzymes of myo-inositol biosynthesis pathway: inositol-x-phosphate synthase (IPS) and inositol-x-phosphate phosphatase (IPP), respectively, were analyzed. 26 DAF seeds displayed the highest expression level of ZmIPS, whereas transcription of ZmIPP was the highest at 13 DAF.

    更新日期:2019-12-17
  • Effect of far-red light exposure on photosynthesis and photoprotection in tomato plants transgenic for the Agrobacterium rhizogenes rolB gene
    J. Plant Physiol. (IF 2.825) Pub Date : 2019-12-12
    Priscilla P. Bettini; Luigi Lazzara; Luca Massi; Fabiola Fani; Maria Luisa Mauro

    Previous work showed in tomato plants harbouring the Agrobacterium rhizogenes rolB gene overexpression of genes involved in chloroplast function and stress response, significant increase in non-photochemical quenching and chlorophyll a and b content, and reduced chlorophyll a/b ratio. The latter condition being typical of plant shade where far-red is dominant, suggested a role for rolB in improving photosynthesis in such condition. To gain a better insight into these results, the photosynthetic performance of transgenic and control plants was compared by means of variable fluorescence kinetics with a WATER-PAM chlorophyll fluorometer, after 6 days-exposure to white light and to a far-red-enriched light source. Photosynthetic parameters analysed were quantum yield of photosystem II photochemistry Y(II); qL, corresponding to the fraction of open PSII reaction centers in a “lake” model of photosystem II; non-photochemical quenching and Y(NO), describing, respectively, regulated and non-regulated pathways for dissipation of excess energy. Chlorophyll a and b content was also analysed by HPLC. Finally, real-time PCR was performed to quantify the expression level of some of the chloroplast-related genes already shown to be overexpressed in transgenic plants. Quantum yield of photosystem II photochemistry decreased with increasing light intensity, showing no significant differences in both plant genotypes and light regimen. qL, on the other hand, was significantly higher at low PAR intensities, in particular in FR-treated transgenic plants. Fate of remaining light energy, channeled into regulated or non-regulated dissipation pathways, was different in transgenic and control plants, indicating a higher capability for protection from photodamage in rolB plants, particularly after exposure to far-red-enriched light. Chlorophyll a/b ratio was also decreased in transgenic plants under far-red-enriched light with respect to white light. Finally, qPCR showed that the expression of genes encoding small heat shock protein, chlorophyll a/b binding protein and carbonic anhydrase was significantly induced by far-red-enriched condition. Taken together, these data suggest the involvement of rolB in photosynthesis modulation under far-red-rich light in tomato.

    更新日期:2019-12-13
  • Factors regulating the differential uptake of persistent organic pollutants in cucurbits and non-cucurbits
    J. Plant Physiol. (IF 2.825) Pub Date : 2019-12-11
    Aya Iwabuchi, Nonoka Katte, Mizuki Suwa, Junya Goto, Hideyuki Inui

    Contamination with persistent organic pollutants (POPs) has become a worldwide concern owing to their the toxicity to humans and wildlife. Pumpkin, cucumber, and squash (Cucurbitaceae) accumulate POPs in their shoots in concentrations higher than those in non-cucurbits; to elucidate the underlying molecular mechanisms of this accumulation, POP transporters were analyzed in the xylem sap of cucurbits and non-cucurbits. The 17-kDa xylem sap proteins detected in all cucurbits but not in non-cucurbits readily bound polychlorinated biphenyl (PCB) in all tested cucurbits, except in cucumber and loofah, and to dieldrin in all tested cucurbits. Ten genes encoding major latex-like proteins (MLPs) responsible for the accumulation of PCBs in zucchini plants were cloned from cucurbits. Phylogenetic analysis using MLP sequences identified two separate clades, one containing Cucurbitaceae MLPs and the other containing those of non-cucurbit members. Recombinant MLPs bound PCB and dieldrin. Western blotting with anti-MLP antibodies identified translocatable and non-translocatable MLPs between root and stem xylem vessels. Translocation of MLPs from the root to stem xylem vessels and POP-binding ability of MLPs are important for selective accumulation of MLPs in cucurbits. This study provides basic knowledge about phytoremediation through overexpression of MLP genes and for breeding cucurbits that accumulate less contaminants.

    更新日期:2019-12-11
  • Gross and net nitrogen export from leaves of a vegetative C4 grass
    J. Plant Physiol. (IF 2.825) Pub Date : 2019-12-07
    Fang Yang, Rudi Schäufele, Hai Tao Liu, Ulrike Ostler, Hans Schnyder, Xiao Ying Gong

    Nitrogen (N) mobilization from mature leaves plays a key role in supplying amino acids to vegetative and reproductive sinks. However, it is unknown if the mobilized N is predominantly sourced by net N-export (a senescence-related process) or other source of N-export from leaves. We used a new approach to partition gross and net N-export from leaf blades at different developmental stages in Cleistogenes squarrosa (a perennial C4 grass). Net N-export was determined as net loss of leaf N with age, while gross N-export was quantified from isotopic mass balances obtained following 24 h-long 15N-labeling with nitrate on 10-12 developmentally distinct (mature and senescing) leaves of individual major tillers. Net N-export was apparent only in older leaves (leaf no. > 7, with leaves numbered basipetally from the tip of the tiller and leaf no. 2 the youngest fully-expanded leaf), while gross N-export was largely independent of leaf age category and was ˜8.4 times greater than the net N-export of a tiller. At whole-tiller level, N import compensated 88 ± 14 (SE) % of gross N-export of all mature blades leading to a net N export of 0.51 ± 0.07 (SE) μg h-1 tiller-1. N-import was equivalent to 0.09 ± 0.01 (SE) d-1 of total leaf N, similar to reported rates of leaf protein turnover. Gross N-export from all mature blades of a tiller was ˜1.9-times the total demand of the immature tissues of the same (vegetative) tiller. Significant N-export is evident in all mature blades, and is not limited to senescence conditions, implying a much shorter mean residence time of leaf N than that calculated from net N-export. Gross N-export contributes not only to the N demand of the immature tissues of the same tiller but also to N supply of other sinks, such as newly formed tillers. N dynamics at tiller level is integrated with that of the remainder of the shoot, thus highlights the importance of integration of leaf-, tiller-, and plant-scale N dynamics.

    更新日期:2019-12-07
  • Plasma membrane ATPase and the aquaporin HvPIP1 in barley brassinosteroid mutants acclimated to high and low temperature
    J. Plant Physiol. (IF 2.825) Pub Date : 2019-11-28
    Iwona Sadura, Marta Libik-Konieczny, Barbara Jurczyk, Damian Gruszka, Anna Janeczko

    The integral parts of the cell membranes are the functional proteins, which are crucial for cell life. Among them, proton-pumping ATPase and aquaporins appear to be of particular importance. There is some knowledge about the effect of the temperature during plant growth, including stress-inducing temperatures, on the accumulation of the membrane proteins: plasma membrane H+-ATPase and aquaporins, but not much is known about the effect of the phytohormones (i.e. brassinosteroids (BR)) on control of accumulation of these proteins. The aim of our study was to answer the question of how a BR deficit and disturbances in the BR perception/signalling affect the accumulation of plasma membrane H+-ATPase (PM H+-ATPase), the aquaporin HvPIP1 transcript and protein in barley growing at 20 °C and during its acclimation at 5 °C and 27 °C. For the studies, the BR-deficient mutant 522DK (derived from the wild-type Delisa), the BR-deficient mutant BW084 and the BR-signalling mutant BW312 and their wild-type Bowman were used. Generally, temperature of growth was significant factor influencing on the level of the accumulation of the H+-ATPase and HvPIP1 transcript and the PM H+-ATPase and HvPIP1 protein in barley leaves. The level of the accumulation of the HvPIP1 transcript decreased at 5 °C (compared to 20 °C), but was higher at 27 °C than at 20 °C in the analyzed cultivars. In both cultivars the protein HvPIP1 was accumulated in the highest amounts at 27 °C. On the other hand, the barley mutants with a BR deficiency or with BR signalling disturbances were characterised by an altered accumulation level of PM H+-ATPase, the aquaporin HvPIP1 transcript and protein (compared to the wild types), which may suggest the involvement of brassinosteroids in regulating PM H+-ATPase and aquaporin HvPIP1 at the transcriptional and translational levels.

    更新日期:2019-11-28
  • Biochemical and histological characterization of succulent plant Tacitus bellus response to Fusarium verticillioides infection in vitro
    J. Plant Physiol. (IF 2.825) Pub Date : 2019-11-27
    Tijana Cvetić Antić, Dušica Janošević, Vuk M. Maksimović, Miroslav Živić, Snežana Budimir, Jasmina Glamočlija, Aleksandra Lj. Mitrović

    We present changes in Tacitus bellus antioxidative system that specifically correspond to subsequent phases of hemibiotroph Fusarium verticillioides infection revealed by histological analysis. T. bellus response to spore germination 6 hours post inoculation (hpi), manifested as first oxidative burst, was characterized by transient decrease in malondialdehyde (MDA) content, transient increase in catalase (CAT), low level of superoxide dismutase (SOD) and peroxidase (POD) activity, as well as with transient decrease in total antioxidant capacity (TAC), total phenol content (TPC) and phenylalanine ammonium lyase activity (PAL), and no changes in polyphenol oxidase (PPO) activity, or phenolic profile. During the biotrophic phase of F. verticillioides infection, characterized by hyphae spread intercellularly in epidermal and mesophyll tissue, the host antioxidative system was suppressed. The transition to necrotrophic phase of F. verticillioides infection (inter- and intracellular colonization and sporulation), occurred 3 - 4 days post inoculation (dpi). During the necrotrophic phase, 5 - 7 dpi, slowed progression of colonization of T. bellus mesophyll cells occurred and it coincided with sharp increase in MDA content and CAT, SOD and POD activities, but the drop in TAC, TPC content, and PPO activity, as well as the production of phytotoxin fusaric acid. Presented results add to the knowledge of events and mechanisms related to the transition from biotrophy to necrotrophy in F. verticillioides.

    更新日期:2019-11-28
  • Root cultures of potato mutant lacking MSPI isoform, indispensable for photosynthetic light reactions, exhibit characteristics similar to intact plant roots
    J. Plant Physiol. (IF 2.825) Pub Date : 2019-11-27
    Hana Ševčíková, Petra Mašková, Helena Lipavská

    Potato (Solanum tuberosum) mutant (ST) lacking one isoform of manganese-stabilizing protein (MSPI) of photosystem II exhibited besides spontaneous tuberization also growth changes with strongly impaired root system development. Previous studies revealed marked changes in carbohydrate levels and allocation within ST plant body. To verify causal relationship between changed carbohydrate balance and root growth restriction we engaged dark grown sucrose-supplied root organ-cultures of ST plants to exclude/confirm shoot effects. Unexpectedly, in ST root cultures we observed large alterations in growth and architecture as well as saccharide status similar to those found in the intact plant roots. The gene expression analysis, however, proved PsbO1 transcript (coding MSPI protein) neither in ST nor in WT root-organ cultures. Therefore, the results point to indirect effects of PsbO1 allele absence connected possibly with some epigenetic modulations.

    更新日期:2019-11-28
  • Increase in cytotoxic lignans production after smut infection in sugar cane plants
    J. Plant Physiol. (IF 2.825) Pub Date : 2019-11-27
    Elena Sánchez-Elordi, Roberto M. Sterling, Rocío Santiago, Roberto de Armas, Carlos Vicente, M. Estrella Legaz

    Smut infection alters the transcription of dirigent proteins (DIR) by sugarcane plants. Here, we show that these alterations are associated to an elevated production of cytotoxic lignans. Smut-resistant sugarcane varieties display a fivefold increase in pinoresinol and also produce elevated amounts of secoisolariciresinol. Conversely, smut-sensitive varieties do not produce pinoresinol or secoisolariciresinol upon infection, synthesizing instead small amounts of matairesinol. Our data indicate that commercial pinoresinol and secoisolariciresinol seem to prevent smut teliospore germination and sporidia release from sprouted teliospores. Consistently, we observed abundant morphological alterations of sporidia incubated in the presence of these lignans. However, commercial lignans do not block the development of the pathogen in a definitive way. Additional experiments demonstrate that only the extracts from healthy or smut-exposed resistant plants inhibit sporidia growth in vitro, indicating that a specific mixture of lignans from resistant plants is necessary to constitute an effective defense mechanism.

    更新日期:2019-11-27
  • Differential partitioning of thiols and glucosinolates between shoot and root in Chinese cabbage upon excess zinc exposure
    J. Plant Physiol. (IF 2.825) Pub Date : 2019-11-26
    Tahereh A. Aghajanzadeh, Dharmendra H. Prajapati, Meike Burow

    Zinc (Zn) is one of the important elements of plant growth, however, at elevated level it is toxic. Exposure of Chinese cabbage to elevated Zn2+ concentrations (5 and 10 µM ZnCl2) resulted in enhancement of total sulfur and organic sulfur concentration. Transcript level of APS reductase (APR) as a key enzyme in biosynthesis of primary sulfur compounds (cysteine and thiols), was up-regulated in both shoot and root upon exposure to elevated Zn2+, which was accompanied by an increase in the concentration of cysteine in both tissues. In contrast, the concentration of thiols increased only in the root by 5.5 and 15-fold at 5 and 10 µM Zn2+, respectively, which was in accompanied by an upregulation of ATP sulfurylase, an enzyme responsible for activation of sulfate. An elevated content of glucosinolates, mostly indolic glucosinolates, only in the shoot of plants exposed to excess level of Zn2+ coincided with an increase in gene expression of key biosynthetic enzymes and regulators (CYP79B3, CYP83B1, MYB34). Thus distinct acuumulation patterns of sulfur containing compounds in root and shoot of Chinese cabbage may be a strategy for Chinese cabbage to combat with exposure to excess Zn.

    更新日期:2019-11-27
  • Polyamines treatment during pollen germination and pollen tube elongation in tobacco modulate reactive oxygen species and nitric oxide homeostasis
    J. Plant Physiol. (IF 2.825) Pub Date : 2019-11-26
    Peter Benko, Shyam Jee, Nikolett Kaszler, Attila Fehér, Katalin Gémes

    Several signaling pathways have been shown to be involved in the regulation of pollen germination and pollen tube elongation. Among others, exogenously applied polyamines were found to strongly affect pollen maturation, pollen tube emergence and elongation. In this study, our aim was to investigate the regulatory relation among exogenous polyamines, and endogenous reactive oxygen species and nitric oxide under pollen germination and the apical growth of pollen tube in tobacco plants. We have found that the various polyamines differentially affected the metabolism of nitric oxide and reactive oxygen species during the processes of pollen germination in the grain and the lengthening pollen tube. It is hypothesized that their differential effects might be related to their distinct influence on the endogenous nitric oxide and reactive oxygen species levels.

    更新日期:2019-11-27
  • Cell wall components regulate photosynthesis and leaf water relations of Vitis vinifera cv. Grenache acclimated to contrasting environmental conditions
    J. Plant Physiol. (IF 2.825) Pub Date : 2019-11-26
    Margalida Roig-Oliver, Miquel Nadal, María José Clemente-Moreno, Josefina Bota, Jaume Flexas

    Environmental conditions determine plants performance as they shape – among other key factors – leaf features and physiology. However, little is known regarding to the changes occurring in leaf cell wall composition during the acclimation to an environmental stress and, specially, if these changes have an impact on other leaf physiology aspects. In order to induce changes in photosynthesis, leaf water relations and cell wall main components (i.e., cellulose, hemicelluloses and pectins) and see how they co-vary, Vitis vinifera cv. Grenache was tested under four different conditions: (i) non-stress conditions (i.e., control, with high summer temperature and irradiance), (ii) growth chamber conditions, (iii) growth chamber under water stress and (iv) cold growth chamber. Plants developed in growth chambers decreased net CO2 assimilation (AN) and mesophyll conductance (gm) compared to control. Although cold did not change the bulk modulus of elasticity (ε), it decreased in growth chamber conditions and water stress. Control treatment showed the highest values for photosynthetic parameters and ε as well as for leaf structural traits such as leaf mass area (LMA) and leaf density (LD). Whereas cellulose content correlated with photosynthetic parameters, particularly AN and gm, pectins and the amount of alcohol insoluble residue (AIR) – an approximation of the isolated cell wall fraction – correlated with leaf water parameters, specifically, ε. Although preliminary, our results suggest that cell wall modifications due to environmental acclimations can play a significant role in leaf physiology by affecting distinctly photosynthesis and water relations in a manner that might depend on environmental conditions.

    更新日期:2019-11-27
  • Leaf ecophysiological and metabolic response in Quercus pyrenaica Willd seedlings to moderate drought under enriched CO2 atmosphere
    J. Plant Physiol. (IF 2.825) Pub Date : 2019-11-26
    Ismael Aranda, Estrella Cadahía, Brígida Fernández de Simón

    Impact of drought under enriched CO2 atmosphere on ecophysiological and leaf metabolic response of the sub-mediterranean Q. pyrenaica oak was studied. Seedlings growing in climate chamber were submitted to moderate drought (WS) and well-watered (WW) under ambient ([CO2]amb =400 ppm) or CO2 enriched atmosphere ([CO2]enr =800 ppm). The moderate drought endured by seedlings brought about a decrease in leaf gas exchange. However, net photosynthesis (Anet) was highly stimulated for plants at [CO2]enr. There was a decrease of the stomatal conductance to water vapour (gwv) in response to drought, and a subtle trend to be lower under [CO2]enr. The consequence of these changes was an important increase in the intrinsic leaf water use efficiency (WUEi). The electron transport rate (ETR) was almost a 20 percent higher in plants at [CO2]enr regardless drought endured by seedlings. The ETR/Anet was lower under [CO2]enr, pointing to a high capacity to maintain sinks for the uptake of extra carbon in the atmosphere. Impact of drought on the leaf metabolome, as a whole, was more evident than that from [CO2] enrichment of the atmosphere. Changes in pool of non-structural carbohydrates were observed mainly as a consequence of water deficit including increases of fructose, glucose, and proto-quercitol. Most of the metabolites affected by drought back up to levels of non-stressed seedlings after rewetting (recovery phase). It can be concluded that carbon uptake was stimulated by [CO2]enr, even under the stomatal closure that accompanied moderate drought. In the last, there was a positive effect in intrinsic water use efficiency (WUEi), which was much more improved under [CO2]enr. Leaf metabolome was little responsible and some few metabolites changed mainly in response to drought, with little differences between [CO2] growth conditions.

    更新日期:2019-11-27
  • Functional identification of apple MdMYB2 gene in phosphate-starvation response
    J. Plant Physiol. (IF 2.825) Pub Date : 2019-11-26
    Yu-Ying Yang, Yi-Ran Ren, Peng-Fei Zheng, Feng-Jia Qu, Lai-Qing Song, Chun-Xiang You, Xiao-Fei Wang, Yu-Jin Hao

    Inorganic phosphate (Pi) starvation severely affects the normal growth and development of plants. Here, a Pi-responsive gene, named MdMYB2 (MDP0000823458), was cloned and functionally identified in apple. Overexpression of MdMYB2 regulated the expression of Pi starvation-induced (PSI) genes and then promoted phosphate assimilation and utilization. The ectopic expression of MdMYB2 in Arabidopsis influenced plant growth and flowering, which was partially rescued by application of exogenous gibberellin (GA). These results indicated that MdMYB2 may be an essential regulator in phosphate utilization and GA-regulated plant growth and development.

    更新日期:2019-11-27
  • Reduced C-to-U RNA editing rates might play a regulatory role in stress response of Arabidopsis
    J. Plant Physiol. (IF 2.825) Pub Date : 2019-11-20
    Duan Chu, Lai Wei

    C-to-U RNA editing is prevalent in the mitochondrial and chloroplast genes in plants. The C-to-U editing rates are constantly very high. During genome evolution, those edited cytidines are likely to be replaced with thymidines at the DNA level. C-to-U editing events are suggested to be designed for reversing the unfavorable T-to-C DNA mutations. Despite the existing theory showing the importance of editing mechanisms, few studies have investigated the genome-wide adaptive signals of the C-to-U editome or the potential function of C-to-U editing events in the stress response. By analyzing the transcriptome and translatome data of normal and heat-shocked Arabidopsis thaliana and the RNA-seq from cold-stressed plants, combined with genome-wide comparison of mitochondrial/chloroplast genes and nuclear genes from multiple aspects, we present the conservational and translational features of each gene and depict the dynamic mitochondrial/chloroplast C-to-U RNA editome. We found that the tAI (tRNA adaptation index) and basic translation levels are lower for mitochondrial/chloroplast genes than for nuclear genes. Interestingly, although we found adaptive signals for the global C-to-U RNA editome in mitochondrial/chloroplast genes, the C-to-U (T) alteration would usually cause a reduction in the codon tAI value. Moreover, the C-to-U editing rates are significantly reduced under heat or cold stress when compared to the normal condition. This reduction is irrelevant to the temperature-sensitive RNA structures. Several cases have illustrated that under heat stress, the reduced C-to-U editing rates alleviate ribosome stalling and consequently facilitate the local translation. Our study reveals that in Arabidopsis thaliana the mitochondrial/chloroplast C-to-U RNA editing rates are reduced under heat or cold stress. This reduction is associated with the alleviation of decreased tAI/translation rate of edited codons. The regulation of C-to-U editing rates could be the tradeoff between quantity and quality. We profile the dynamic change of C-to-U RNA editome under heat stress and propose a potential role of editing sites in the heat response. Our work should be appealing to the plant physiologists as well as the RNA editing community.

    更新日期:2019-11-21
  • The ethylene response factor SmERF8 regulates the expression of SmKSL1 and is involved in tanshinone biosynthesis in Saliva miltiorrhiza hairy roots
    J. Plant Physiol. (IF 2.825) Pub Date : 2019-07-09
    Zhenqing Bai, Wenli Huang, Jie Jiao, Chenlu Zhang, Zhuoni Hou, Kaijing Yan, Xuemin Zhang, Ruilian Han, Zongsuo Liang

    Saliva miltiorrhiza ethylene response factor (SmERF), predicted to be expressed genome-wide, is the potential regulator of tanshinone biosynthesis. However, few studies have investigated its transcriptional regulation pathways in tanshinone biosynthesis. Here, we report an ethylene response factor (SmERF8), which was screened by the SmKSL1 (a key gene in tanshinone biosynthesis) promoter from the S. miltiorrhiza cDNA library. The SmERF8, highly expressed in S. miltiorrhiza root head, is sensitive to Eth stress, and its protein was enriched in the nucleus. The SmERF8 recognizes the GCC-box in the SmKSL1 promoter. Overexpression and RNAi of SmERF8 in S. miltiorrhiza transgenic hairy roots showed that the tanshinone contents were significantly increased in the overexpression transgenic lines and decreased in RNAi lines. These results suggest that the SmERF8 may be a central activator that regulates the expression of SmKSL1 by binding the GCC-box and then promoting tanshinone biosynthesis. Thus, the SmERF8 may functionally accelerate tanshinone biosynthesis by the transcriptional regulation of its key gene.

    更新日期:2019-11-18
  • The possible bottleneck effect of polyamines’ catabolic enzymes in efficient adventitious rooting of two stone fruit rootstocks with different rooting capacity even under high endogenous polyamine titers
    J. Plant Physiol. (IF 2.825) Pub Date : 2019-06-13
    Athanasios Tsafouros, Peter A. Roussos

    Adventitious rooting is an important plant physiological response utilized in cutting propagation, a procedure with high financial significance. Many endogenous factors are involved, such as plant growth regulators, carbohydrates, minerals, polyamines etc. The objective of the present study was to investigate the role of polyamines and polyamine catabolic enzymes in the bases of softwood cuttings of two Prunus rootstocks, during the early phases of rhizogenesis. An easy-to-root and a difficult-to-root rootstock were studied, concerning their polyamine content (in free, soluble conjugate and insoluble bound form), polyamine catabolic enzyme activities (polyamine oxidase, PAO and diamine oxidase, DAO) and catalase activity, with and without the effect of indole-3-butyric acid as rooting hormone, during the early phases of rhizogenesis. Putrescine, spermine and their catabolic product, H2O2, were applied in the bases of leafy cuttings, in order to increase the rooting percentage of the recalcitrant species. Spermine was not detected in the difficult to root rootstock, which exhibited higher titer of putrescine and spermidine, PAO and catalase activity, but lower DAO activity compared to the easy-to-root one. The rooting percentage of the recalcitrant species was doubled under spermine and H2O2 application. The results obtained, highlighted the role of polyamine catabolic enzymes and indirectly the role of the polyamine catabolic product H2O2 as more significant than the polyamine content per se in adventitious rooting of the specific stone fruit rootstocks.

    更新日期:2019-11-18
  • Better salinity tolerance in tetraploid vs diploid volkamer lemon seedlings is associated with robust antioxidant and osmotic adjustment mechanisms
    J. Plant Physiol. (IF 2.825) Pub Date : 2019-11-04
    Muhammad Fasih Khalid, Sajjad Hussain, Muhammad Akbar Anjum, Shakeel Ahmad, Muhammad Arif Ali, Shaghef Ejaz, Raphael Morillon

    Tetraploids are usually more tolerant to environmental stresses than diploids. Citrus plants face numerous abiotic stresses, including salinity, which negatively affect growth and yield. Double diploid citrus rootstocks have been shown to be more tolerant to abiotic stresses than their diploid relatives. In this study, we evaluated the antioxidative and osmotic adjustment mechanisms of diploid (2x) and double diploid (4x) volkamer lemon (Citrus volkameriana Tan. and Pasq.) rootstocks, which act against salt stress (75 and 150 mM). Results indicated that, under salt stress, all physiological variables (photosynthesis, stomatal conductance, transpiration rate, and leaf greenness) decreased, and these decreases were more noticeable in 2x plants than in 4x plants. On the other hand, accumulation of oxidative markers (malondialdehyde and hydrogen peroxide) was greater in the leaves and roots of 2x seedlings than in 4x seedlings. Similarly, the activities of antioxidative enzymes (peroxidase, ascorbate peroxidase, glutathione reductase, and catalase) were higher in the leaves and roots of 4x plants than in 2x plants. However, superoxide dismutase activity was higher in the roots of 2x seedlings than 4x seedlings. Double diploid plants affected by salt stress accumulated more osmolytes (i.e. proline and glycine betaine) in their leaves and roots than that by 2x plants. Total protein content, antioxidant capacity, and total phenolic content were also higher in 4x plants than 2x plants under salinity. At 150 mM, both 2x and 4x plants showed more symptoms of stress than those at 75 mM. Sodium content was the highest in the roots of 2x plants and in the leaves of 4x plants, while chloride content peaked in the leaves of 2x plants and in the roots of 4x plants. Overall, our results demonstrate that the active antioxidative defence mechanisms of 4x plants increase their tolerance to salinity compared to their corresponding 2x relatives. Thus, the use of newly developed tetraploid rootstocks may be a strategy for enhancing crop production in saline conditions.

    更新日期:2019-11-04
  • Which plant traits are most strongly related to post-silking nitrogen uptake in maize under water and/or nitrogen stress?
    J. Plant Physiol. (IF 2.825) Pub Date : 2019-11-02
    Joshua Nasielski, Hugh Earl, Bill Deen

    The impact of grain yield on post-silking N uptake (PostN) in maize has been a major focus of previous studies, although results are mixed as to the direction and magnitude of the relationship between these two variables. The objective of this study was to understand how grain yield and other plant traits interact with exogenous N and water availability to regulate PostN in maize. In a greenhouse experiment, maize was subjected to high or low levels of N and water supply pre-silking during vegetative growth, which created large variations in source and sink components such as ear size and leaf area. Notably, these large differences in source and sink components were generated not by cutting off plant organs but instead by relying on maize response to vegetative-stage N and water stress. These plants were then subject to high and low levels of N and water supply post-silking, and the relationship between plant traits and PostN was characterized. Final grain yield was irrevocably reduced in the treatments where pre-silking water stress occurred compared to the well-watered pre-silking treatments (30 g plant−1 vs. 106 g plant−1). Because of the reduced ear sink strength in the treatments experiencing pre-silking water stress, post-silking biomass (PostBM) and PostN accumulated in vegetative organs. This resulted in greater PostN at maturity in the lower yielding treatments when post-silking water and/or N stress occurred (1.1 vs. 0.6 g N plant−1). Due to the shift in assimilate and N partitioning towards vegetative organs, leaf CER and root dry weight during grain-fill were better maintained in the lower yielding treatments. We conclude that while biomass accumulation (PostBM) regulates PostN, under post-silking N or water stress, shifting sink organs from the grain to vegetative structures increases PostN by improving vegetative organ function and enhancing post-silking source-sink ratios.

    更新日期:2019-11-04
  • Altered plant organogenesis under boron deficiency is associated with changes in high-mannose N-glycan profile that also occur in animals
    J. Plant Physiol. (IF 2.825) Pub Date : 2019-11-01
    Reguera María, Abreu Isidro, Sentís Carlos, Bonilla Ildefonso, Bolaños Luis

    Boron (B) deficiency affects the development of Pisum sativum nodules and Arabidopsis thaliana root meristems. Both organs show an alteration of cell differentiation that result in the development of tumor-like structures. The fact that B in plants is not only able to interact with components of the cell wall but also with membrane-associated glycoconjugates, led us to analyze changes in high mannose type N-glycans (HMNG). The affinoblots with concanavalin A revealed alterations in the N-glycosylation pattern during early development of nodules and roots under B deprivation. Besides, there is increasing evidence of a B role in animal physiology that brought us to investigate the impact of B deficiency on Danio rerio (zebrafish) development. When B deficiency was induced prior to early cleavage stages, embryos developed as an abnormal undifferentiated mass of cells. Additionally, when B was removed at post-hatching, larvae undergo aberrant organogenesis. Resembling the phenomenon described in plants, alteration of the N-glycosylation pattern occurred in B-deficient zebrafish larvae prior to organogenesis. Overall, these results support a common function of B in plants and animals associated with glycosylation that might be important for cell signaling and cell fate determination during development.

    更新日期:2019-11-01
  • The Diffusive Injection Micropipette (DIMP)
    J. Plant Physiol. (IF 2.825) Pub Date : 2019-11-01
    Alexander H. Howell, Winfried S. Peters, Michael Knoblauch

    The microinjection of fluorescent probes into live cells is an essential component in the toolbox of modern cell biology. Microinjection techniques include the penetration of the plasma membrane and, if present, the cell wall with micropipettes, and the application of pressure or electrical currents to drive the micropipette contents into the cell. These procedures interfere with cellular functions and therefore may induce artifacts. We designed the diffusive injection micropipette (DIMP) that avoids most of the possible artifacts due to the drastically reduced volume of its fluid contents and the utilization of diffusion for cargo delivery into the target cell. DIMPs were successfully tested in plant, fungal, and animal cells. Using the continuity of cytoplasmic dynamics over ten minutes after impalement of Nicotiana trichome cells as a criterion for non-invasiveness, we found DIMPs significantly less disruptive than conventional pressure microinjection. The design of DIMPs abolishes major sources of artifacts that cannot be avoided by other microinjection techniques. Moreover, DIMPs are inexpensive, easy to produce, and can be applied without specific equipment other than a micromanipulator. With these features, DIMPs may become the tool of choice for studies that require the least invasive delivery possible of materials into live cells.

    更新日期:2019-11-01
  • Obituary.
    J. Plant Physiol. (IF 2.825) Pub Date : 2015-06-30
    Karl H Mühling

    更新日期:2019-11-01
  • Poly-beta-hydroxybutyrate accumulation in Nostoc muscorum and Spirulina platensis under phosphate limitation.
    J. Plant Physiol. (IF 2.825) Pub Date : 2006-01-21
    Bhabatarini Panda,Laxuman Sharma,Nirupama Mallick

    Nostoc muscorum and Spirulina platensis were grown under phosphate deficiency in order to investigate the role of internal phosphate pool and activity of alkaline phosphatase on poly-beta-hydroxybutyrate (PHB) accumulation. PHB accumulation in N. muscorum increased to 22.7% of dry weight (dw) after 4 day of phosphate deficiency, while the internal phosphate pool reduced to the level of 0.02 microM mg dw(-1) at a maximum APase activity of 2.57nM PNP mg dw(-1) h(-1). In contrary, S. platensis depicted maxima of 1.39nM PNP mg dw(-1) h(-1) on day 30 of incubation, which was about 2 fold lower than the observed value of N. muscorum. PHB content in S. platensis remained low even after prolonged phosphate starvation, and a rise only up to 3.5% of dw was recorded on day 60 of phosphate deficiency. Supplementation of NADPH exogenously to S. platensis cultures grown under phosphate deficiency favoured PHB accumulation in 10, 20 and 30 days old cultures, but not in the cultures grown under phosphate deficiency for 60 days. The possible role of phosphate limitation on PHB accumulation is discussed.

    更新日期:2019-11-01
  • Green, herbicide-resistant plants by particle inflow gun-mediated gene transfer to diploid bahiagrass (Paspalum notatum).
    J. Plant Physiol. (IF 2.825) Pub Date : 2006-01-21
    Takahiro Gondo,Shin-ichi Tsuruta,Ryo Akashi,Osamu Kawamura,Franz Hoffmann

    We have established an efficient particle-bombardment transformation protocol for the diploid non-apomictic genotype of the warm season forage crop Paspalum notatum (bahiagrass). A vector containing a herbicide resistance gene (bar) together with the GUS reporter gene was used in transformation experiments. The bar gene confers resistance to the herbicide bialaphos. An improved culture system, highly regenerative callus, dense in compact polyembryogenic clusters, was produced on medium with a high CuSO4 content at elevated temperature. Target tissue (360 calli) produced under these conditions yielded 52 rooted plants on herbicide-containing medium, and 22 of these plants were PCR-positive. DNA gel blot analysis revealed a copy number of 1-5 for the GUS gene in different independent transformants. There was no correlation between copy number and GUS activity. While conventional cultures yielded exclusively albino plants on herbicide-containing medium, improved culture conditions for the target tissue resulted in the recovery of 100% green transgenic plants. All green herbicide-resistant regenerants were morphological normal and fertile.

    更新日期:2019-11-01
  • Nucleotide specificity of the RNA editing reaction in pea chloroplasts.
    J. Plant Physiol. (IF 2.825) Pub Date : 2006-01-21
    Yuki Nakajima,R Michael Mulligan

    A sensitive in vitro editing assay for the pea chloroplast petB editing site has been developed and utilized to study the mechanism of C-to-U editing in chloroplast extracts. The in vitro editing assay was characterized by several criteria including: linearity with extract amount; linearity over time; dependence on assay components; and specificity of editing site conversion. The increase in the extent C-to-U conversion of the petB editing site was nearly linear with the amount chloroplast protein extract added, although the reaction appeared to decline in rate after approximately 30 min. The assay was tested for the importance of various assay components, and the omission of protease inhibitor and ATP was shown to dramatically reduce the extent of the editing reaction. Sequence analysis of cDNA clones obtained after an in vitro editing reaction demonstrated that 12 of 17 (71%) clones were edited, and that no other nucleotide changes in these cDNAs were detected. Thus, the fidelity and specificity of the in vitro editing system appears to be excellent, and this system should be suitable to study both mechanism of the editing reaction and editing site selection. The in vitro editing reaction was strongly stimulated by the addition of ATP, and all four NTPs and dNTPs stimulated the editing reaction except for rGTP, which had no effect. Thus, the nucleotide specificity of the editing reaction is broad, and is similar in this respect to the mitochondrial editing system. Most enzyme or processes specifically utilize ATP or GTP for phosphorylation and the ability to substitute other NTPs and dNTPs is unusual. RNA helicases have a similar broad nucleotide specificity and this may reflect the involvement of an RNA helicase in plant organelle editing.

    更新日期:2019-11-01
  • Nitric oxide reduces Cu toxicity and Cu-induced NH4+ accumulation in rice leaves.
    J. Plant Physiol. (IF 2.825) Pub Date : 2006-01-21
    Chia Chi Yu,Kuo Tung Hung,Ching Huei Kao

    Nitric oxide (NO) is a highly reactive, membrane-permeable free radical, which has recently emerged as an important antioxidant. Here we investigated the protective effect of NO against the toxicity and NH4+ accumulation in rice leaves caused by excess CuSO4 (10mmol L(-1)). It was found that free radical scavengers (sodium benzoate, thiourea, and reduced glutathione) reduced the toxicity and NH4+ accumulation in rice leaves caused by excess CuSO4. NO donor sodium nitroprusside (SNP) was also effective in reducing CuSO4-induced toxicity and NH4+ accumulation in rice leaves. The protective effect of SNP on the toxicity and NH4+ accumulation can be reversed by 2-(4-carboxy-2-phenyl)-4,4,5,5-tetramethyl- imidazoline-1-oxyl-3-oxide, a NO scavenger, suggesting that the protective effect of SNP is attributable to NO released. Results obtained in the present study suggest that reduction of CuSO4-induced toxicity and NH4+ accumulation by SNP is most likely mediated through its ability to scavenge active oxygen species.

    更新日期:2019-11-01
  • Effects of 6-methoxy-2-benzoxazolinone on the germination and alpha-amylase activity in lettuce seeds.
    J. Plant Physiol. (IF 2.825) Pub Date : 2006-01-21
    Hisashi Kato-Noguchi,Francisco A Macías

    Germination of lettuce seeds was inhibited by 6-methoxy-2-benzoxazolinone (MBOA) at concentrations greater than 0.03 mmol/L. MBOA also inhibited the induction of alpha-amylase activity in the lettuce seeds at concentrations greater than 0.03 mmol/L. These two concentration-response curves for the germination and alpha-amylase indicate that the percentage of the germination was positively correlated with the activity of alpha-amylase in the seeds. Lettuce seeds germinated around 18h after incubation and inhibition of alpha-amylase by MBOA occurred within 6h after seed incubation. These results show that MBOA may inhibit the germination of lettuce seeds by inhibiting the induction of alpha-amylase activity.

    更新日期:2019-11-01
  • HPLC screening of natural vitamin E from mediterranean plant biofactories--a basic tool for pilot-scale bioreactors production of alpha-tocopherol.
    J. Plant Physiol. (IF 2.825) Pub Date : 2005-12-03
    G Sivakumar,L Bacchetta,R Gatti,G Zappa

    The study was performed in order to investigate a simple, efficient, reliable and rapid method of extracting and quantifying natural vitamin E for pressurized liquid extraction (PLE) as well as high-performance liquid chromatography (HPLC) analysis. Lyophilized Corylus avellana L. nut samples were powdered by high-speed milling with Waring blender for 40 s. alpha-Tocopherol was extracted from the nut tissue powder using dehydrated hexane fortified with 0.01% butylated hydroxytoluene (BHT, co-antioxidant). The rate of alpha-tocopherol accumulation showed differences among nut samples collected in different areas of Italy. Sarda Piccola nut biofactory contained higher amount (81.17 microg/g d.w) of alpha-tocopherol than other-local eleven Italian cultivar nuts. These results provide insight into the biofactory basis for alpha-tocopherol accumulation in hazelnut and give the suitable cultivar tissues to establish pilot-scale bioreactors production of natural bioactive vitamin E.

    更新日期:2019-11-01
  • Phytochelatin plays a role in UV-B tolerance in N2-fixing cyanobacterium Anabaena doliolum.
    J. Plant Physiol. (IF 2.825) Pub Date : 2005-12-03
    Poonam Bhargava,Ashish Kumar Srivastava,Snigdha Urmil,Lal Chand Rai

    To study the role of Cd-induced phytochelatins in UV-B tolerance, lipid peroxidation, antioxidative enzymes (superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase), glutathione arid phytochelatin contents were measured in buthionine sulphoximine treated and untreated cells of Anabaena doliolum. Cd-pretreatment of the cyanobacterium reduced the lipid peroxidation as well as the antioxidative enzymes in comparison to UV-B treatment alone, whereas the phytochelatin content demonstrated an increase. In contrast to this, buthionine sulphoximine-induced inhibition of phytochelatin synthase, dramatically decreased the Cd-induced co-tolerance against UV-B, hence demonstrating that phytochelatin not only protects the cyanobacterium from heavy metal but participates in UV-B tolerance as well.

    更新日期:2019-11-01
  • Heavy metal stress reduces the deposition of calcium oxalate crystals in leaves of Phaseolus vulgaris.
    J. Plant Physiol. (IF 2.825) Pub Date : 2005-11-01
    David Jáuregui-Zùñiga,Maria Angeles Ferrer,Antonio A Calderón,Romualdo Muñoz,Abel Moreno

    Calcium oxalate (CaOx) crystals in plants may serve as a sink for the absorption of excess calcium, and they could play an important role in heavy metal detoxification. In this study, the effect of heavy metals and different calcium concentrations on the growth of calcium oxalate crystals in leaves of Phaseolus vulgaris was investigated. Different analytical techniques were used to determine the influence of exogenous lead and zinc on CaOx deposition and to detect a presence of these metals in CaOx crystals. We found a positive correlation between the calcium concentration in the nutrient medium and the production of calcium oxalate crystals in leaves of hydroponically grown plants. On the other hand, addition of the heavy metals to the nutrient medium decreased the number of crystals. Energy dispersive X-ray spectrometry did not detect the inclusion of heavy metals inside the CaOx crystals. Our investigation suggests that CaOx crystals do not play a major role in heavy metal detoxification in P. vulgaris but do play an important role in bulk calcium regulation.

    更新日期:2019-11-01
  • Hydrogen peroxide pre-treatment induces salt-stress acclimation in maize plants.
    J. Plant Physiol. (IF 2.825) Pub Date : 2005-11-01
    André Dias de Azevedo Neto,José Tarquinio Prisco,Joaquim Enéas-Filho,Jand-Venes Rolim Medeiros,Enéas Gomes-Filho

    The effect of exogenously applied H2O2 on salt stress acclimation was studied with regard to plant growth, lipid peroxidation, and activity of antioxidative enzymes in leaves and roots of a salt-sensitive maize genotype. Pre-treatment by addition of 1 microM H2O2 to the hydroponic solution for 2 days induced an increase in salt tolerance during subsequent exposure to salt stress. This was evidenced by plant growth, lipid peroxidation and antioxidative enzymes measurements. In both leaves and roots the variations in lipid peroxidation and antioxidative enzymes (superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase, glutathione reductase, and catalase) activities of both acclimated and unacclimated plants, suggest that differences in the antioxidative enzyme activities may, at least in part, explain the increased tolerance of acclimated plants to salt stress, and that H2O2 metabolism is involved as signal in the processes of maize salt acclimation.

    更新日期:2019-11-01
  • Carotenogenic gene expression and ultrastructural changes during development in marigold.
    J. Plant Physiol. (IF 2.825) Pub Date : 2005-09-22
    Alma A Del Villar-Martínez,Pedro A García-Saucedo,Alfonso Carabez-Trejo,Andrés Cruz-Hernández,Octavio Paredes-Lópeza

    Marigold (Tagetes erecta) flowers are a good source of carotenoids and can be used as a model studies on pigmentation during flower development. They show different levels of pigmentation caused by lutein. Here we describe the expression of several genes in the carotenoid biosynthetic pathway: phytoene synthase (Psy), phytoene desaturase (Pds), lycopene beta-cyclase (Lcy-b) and lycopene epsilon-cyclase (Lcy-e). cDNA inserts from isolated clones were 1376-1916bp long. The predicted amino acid sequences showed from 66 to 100% homology with other reported sequences (NCBI gene bank). Northern blot analyses of three varieties of marigold showed that most gene transcripts were expressed during flower development. The ultrastructural changes that occurred during plastid differentiation in flower morphogenesis were analyzed, and pigment accumulation among varieties was evaluated. The pigment deposition in specific structures (lipidic vesicles) during flower development was demonstrated.

    更新日期:2019-11-01
  • Induction of multiple shoots from leaf segments, in vitro-flowering and fruiting of a dwarf tomato (Lycopersicon esculentum).
    J. Plant Physiol. (IF 2.825) Pub Date : 2005-09-09
    Kokkirala Venugopal Rao,Kasula Kiranmayee,Umate Pavan,Telakalapalli Jaya Sree,Alleni V Rao,Abbagani Sadanandam

    Multiple shoots were induced from leaf explants of Lycopersicon esculentum cultivar MicroTom, within 20-25d, on MS medium supplemented with 8.9 microM benzylaminopurine (BAP)+1.14 microM indole-3-acetic acid (IAA). For rooting, elongated microshoots were excised and transferred onto MS medium supplemented with 4.9 microM indole-3-butyric acid (IBA). Well-developed roots and flower raceme were obtained on d 7 and 13, respectively, upon transfer of the microshoots onto rooting medium. The flowers self-fertilized in vitro and produced mature fruits in additional 15-17d of culture.

    更新日期:2019-11-01
  • Hydrogen peroxide mediates defence responses induced by chitosans of different molecular weights in rice.
    J. Plant Physiol. (IF 2.825) Pub Date : 2005-09-09
    Wuling Lin,Xiangyang Hu,Wenqing Zhang,W John Rogers,Weiming Cai

    To investigate the mechanisms whereby treatment with chitosan (CHN) is observed to increase the capacity of plants to resist pathogens, CHNs of different molecular weights (MWs) prepared by enzyme hydrolysis were used to treat rice cells in suspension culture and also rice seedlings. The results obtained with cultured cells showed that in this material CHN treatment could trigger a set of defence responses, including the production of hydrogen peroxide (H2O2), increases in the activities of phenylalanine ammonialyase (PAL; EC 4.3.1.5) and chitinase (CHI; EC 3.2.1.14), increases in transcription of defence-related genes beta-1,3-glucanase (glu) and chitinase (chi) and accumulation of pathogen-related protein (PR1). Furthermore, CHNs of different MWs were observed to have different capacities to induce defence responses. CHNs of low MWs were more effective at inducing the described defence responses than those of higher MWs. Enhanced defence against rice blast pathogen Magnaporthe grisea 97-23-2D1 was observed in rice seedlings treated with low MW CHNs compared to seedlings treated with higher MW CHNs. In all cases, suppressing the production of H2O2 by adding scavengers dimethylthiourea (DMTU), 2,5-dihydroxycinnamic acid methyl ester (DHC), catalase (Cat) or ascorbate (As) blocked the defence responses. These results indicate that CHNs of low MWs have a greater capacity to induce the production of H2O2, thus resulting in stronger defence responses, than those with higher MWs.

    更新日期:2019-11-01
  • Boron deficiency increases putrescine levels in tobacco plants.
    J. Plant Physiol. (IF 2.825) Pub Date : 2005-09-09
    Juan J Camacho-Cristóbal,José M Maldonado,Agustín Gonzláez-Fontes

    Polyamine concentrations were determined in leaves and roots of tobacco plants (Nicotiana tabacum L.) subjected to a short-term boron deficiency. A decrease in the growth of shoots and, especially, roots was found under this mineral deficiency. Boron deficiency did not lead to a significant decrease in leaf or root ion concentrations when compared to control treatment; however, as expected, leaf boron concentration was lower in boron-deficient plants in comparison to the control. In leaves, the levels of free putrescine and spermidine were similar in both treatments. In roots, a short-term boron deficiency caused an increase in free putrescine. Moreover, boron-deficient plants had higher conjugated polyamine concentration than boron-sufficient plants, which was especially evident for conjugated putrescine in leaves. A possible link between boron and polyamine levels is proposed and discussed.

    更新日期:2019-11-01
  • Rice fatty acid alpha-dioxygenase is induced by pathogen attack and heavy metal stress: activation through jasmonate signaling.
    J. Plant Physiol. (IF 2.825) Pub Date : 2005-09-09
    Takao Koeduka,Kenji Matsui,Morifumi Hasegawa,Yoshihiko Akakabe,Tadahiko Kajiwara

    Plant fatty acid alpha-dioxygenases (DOXs) catalyze the stereospecific conversion of fatty acids into the corresponding (R)-2-hydroperoxy fatty acids. In several plant species the corresponding gene was shown to be induced by pathogen infection, herbivore attack and environmental stresses. The precise signaling pathway accountable for the induction remains unidentified. In the present study, the effects of bacterial infection, oxidative- and heavy metal-stresses, and plant signaling molecules such as jasmonate, salicylic acid (SA), and ethylene (ET) on expression of a fatty acid alpha-DOX (OsDOX) gene in rice seedlings were investigated. The rice blight bacteria, Xanthomonas oryzae, elicited the accumulation of OsDOX transcripts in the leaves in both the incompatible and compatible interactions. Treating the seedling with CuSO4 also significantly enhanced the OsDOX expression. The degree of induction was shown to be mostly parallel to the level of endogenous jasmonic acid (JA) in the leaves. In contrast, SA was little effective and ET down-regulated not only the OsDOX expression but also the endogenous level of JA in rice seedlings. These results suggested that the OsDOX gene expression by a variety of stress-related stimuli was activated through jasmonate signaling and was negatively regulated by ET.

    更新日期:2019-11-01
  • Modulation of nitrate reductase activity in rice seedlings under aluminium toxicity and water stress: role of osmolytes as enzyme protectant.
    J. Plant Physiol. (IF 2.825) Pub Date : 2005-09-09
    Pallavi Sharma,Rama Shanker Dubey

    Nitrate reductase (NR) activity in the presence of Mg2+ (NR act) representing the non-phosphorylated NR state and the activity in the presence of EDTA (NR max) representing maximum NR activity was measured in roots and shoots of 15 d grown aluminium and water stressed rice seedlings to examine changes in NR activation state due to these stresses. Seedlings subjected to a moderate water stress level of -0.5 MPa for 24 h or grown in presence of 80 microM Al3+showed decreased level of NR max but resulted in higher NR act and NR activation state. However, seedlings grown in presence of a higher level of 160 microM Al3+ showed a decline in NR act as well as NR max. With a higher water stress Level of -2.0MPa a marked decline in the levels of both NR act and NR max was observed, whereas NR activation state remained almost unaltered with severe water stress. NR activity appeared to be sensitive to H2O2, PEG-6000, NaCl and various metal salts. Incorporation of these components in the enzyme assay medium led to decreased affinity of enzyme towards its substrate with increase in Km and decrease in Vmax values. Addition of each of the osmolytes i.e. 1 mol/L proline, 1 mol/L glycine betaine or 1 mol/L sucrose in the enzyme assay medium caused a considerable protection to the enzyme against the damaging effects of stressful components. An enhanced level of proline and glycine betaine was observed in Al-stressed seedlings and sucrose in Al as well as water stressed seedlings. Results suggest that Al toxicity and water stress decrease total amount of functional NR in rice seedlings and the osmolytes proline, glycine betaine and sucrose appear to have a direct protective action on enzyme NR under stressful conditions

    更新日期:2019-11-01
  • Comparative quantification of pharmacodynamic parameters of chiral compounds (RRR- vs. all-rac-alpha tocopherol) by global gene expression profiling.
    J. Plant Physiol. (IF 2.825) Pub Date : 2005-07-13
    Patrick Y Muller,Thomas Netscher,Jan Frank,Elisabeth Stoecklin,Gerald Rimbach,Luca Barella

    Pharmacologically active compounds (e.g. from the groups of pharmaceutical drugs, cofactors or vitamins) often consist of two or more stereoisomers (enantiomers or diastereoisomers) which may differ in their pharmacodynamic/kinetic, toxicological and biological properties. A well-known example is vitamin E which is predominantly administered as two different forms, one derived from natural sources (mainly soybeans), and one from production by chemical total-synthesis. While vitamin E from natural sources occurs as a single stereoisomer (RRR-alpha-tocopherol), synthetic vitamin E (all-rac-alpha-tocopherol) is an equimolar mixture of eight stereoisomers. Based on a number of animal studies it has been suggested that the biological potency of natural-source vitamin E is 1.36 greater compared to its counterpart produced by chemical synthesis. In this study, we have used the Affymetrix GeneChip technology to evaluate the feasibility of a new bio-assay where the gene regulatory activities of RRR-alpha-tocopherol and all-rac-alpha-tocopherol were quantified and compared on the genome-wide level. For this purpose, HepG2 cells were supplemented with increasing amounts of RRR- or all-rac-alpha-tocopherol for 7 days. Genes showing a dose-related induction/repression were identified by global gene expression profiling. Our findings show that RRR- and all-rac-alpha-tocopherol share an identical transcriptional activity, i.e. induce/repress the expression of the same set of genes. Based on the transcriptional dose-response data, EC50 and IC50 values were determined for each of these genes. The feasibility of calculating a "transcriptional potency factor" of RRR- vs. all-rac-e-tocopherol was evaluated by dividing the EC50/IC50 of RRR-alpha-tocopherol by the corresponding EC50/IC50 of all-rac-alpha-tocopherol for every of the vitamin E responsive genes. Using this approach we have calculated 215 single biopotency ratios. Subsequently, the mean of all potency ratios was found to be 1.05. In the present work we propose a new assay for the analysis and comparison of the biological activity and potency of chiral compounds in vivo.

    更新日期:2019-11-01
  • Intracellular signaling mechanisms mediating the antiproliferative and apoptotic effects of gamma-tocotrienol in neoplastic mammary epithelial cells.
    J. Plant Physiol. (IF 2.825) Pub Date : 2005-07-13
    Paul W Sylvester,Sumit J Shah,Ganesh V Samant

    Tocotrienols, a subgroup within the vitamin E family of compounds, display potent antiproliferative and apoptotic activity against neoplastic mammary epithelial cells at treatment doses that have little or no effect on normal cell growth and function. Recent studies have shown that treatment with a growth inhibitory, but non-cytotoxic dose (4 microM) of gamma-tocotrienol inhibits phosphatidylinositol-3-kinase-dependent kinase (Pl3K)/Pl3K-dependent kinase 1 (PDK-1)/mitogenic signaling over a 2-3 day period following treatment exposure, and these effects were not found to be associated with an increased in either phosphatase and tensin homologue deleted from chromosome 10 (PTEN) or protein phosphatase type 2A (PP2A) phosphatase activity. In addition, this treatment caused a large decrease in NFKB transcriptional activity, apparently by suppressing I kappa B-kinase (IKK)-alpha/beta activation, an enzyme associated with inducing NFKB activation. Since Akt and NFkappaB are intimately involved in mammary tumor cell proliferation and survival, these findings strongly suggest that the antiproliferative effects of gamma-tocotrienol result, at least in part, from a reduction in Akt and NFkappa B activity. In contrast, treatment with 20 microM gamma-tocotrienol (cytotoxic dose) resulted in caspase-8 and -3 activation and apoptosis. It was also shown that this same treatment caused a rapid and large decrease in Pl3K/PDK/Akt signaling within 2-4h following treatment exposure, and a corresponding decrease in intracellular levels of FLIP, an antiapoptotic protein that inhibits caspase-8 activation. In summary, both the antiproliferative and apoptotic effects of gamma-tocotrienol appear to be mediated by a reduction in the Pl3K/PDK-1 /Akt signaling, an important pathway associated with cell proliferation and survival in neoplastic mammary epithelial cells.

    更新日期:2019-11-01
  • Improving alpha-tocopherol production in plant cell cultures.
    J. Plant Physiol. (IF 2.825) Pub Date : 2005-07-13
    Rosa Gala,Giovanni Mita,Sofia Caretto

    Suspension cell cultures of Helianthus annuus L. were previously established for the production of the most active component of vitamin E, alpha-tocopherol, by optimizing medium composition and culture conditions. In the present work, the possibility of enhancing alpha-tocopherol production by the addition of jasmonic acid to the culture medium was investigated both in sunflower and Arabidopsis cell cultures. A considerable increase (49% and 66%, respectively) of alpha-tocopherol production was obtained in both, after a 72-h treatment with 5 microM jasmonic acid. The modulation of alpha-tocopherol levels in plant cell cultures can provide useful hints for a regulatory impact on tocopherol metabolism.

    更新日期:2019-11-01
  • The role of alpha-tocopherol in plant stress tolerance.
    J. Plant Physiol. (IF 2.825) Pub Date : 2005-07-13
    Sergi Munné-Bosch

    Environmental stresses trigger a wide variety of plant responses, ranging from altered gene expression to changes in cellular metabolism and growth. A plethora of plant reactions exist to circumvent the potentially harmful effects caused by light, drought, salinity, extreme temperatures, pathogen infections and other stresses. Alpha-tocopherol is the major vitamin E compound found in leaf chloroplasts, where it is located in the chloroplast envelope, thylakoid membranes and plastoglobuli. This antioxidant deactivates photosynthesis-derived reactive oxygen species (mainly 1O2 and OH), and prevents the propagation of lipid peroxidation by scavenging lipid peroxyl radicals in thylakoid membranes. Alpha-tocopherol levels change differentially in response to environmental constraints, depending on the magnitude of the stress and species-sensitivity to stress. Changes in alpha-tocopherol levels result from altered expression of pathway-related genes, degradation and recycling, and it is generally assumed that increases of alpha-tocopherol contribute to plant stress tolerance, while decreased levels favor oxidative damage. Recent studies indicate that compensatory mechanisms exist to afford adequate protection to the photosynthetic apparatus in the absence of alpha-tocopherol, and provide further evidence that it is the whole set of antioxidant defenses (ascorbate, glutathione, carotenoids, tocopherols and other isoprenoids, flavonoids and enzymatic antioxidants) rather than a single antioxidant, which helps plants to withstand environmental stress.

    更新日期:2019-11-01
  • Defects in root development and gravity response in the aem1 mutant of rice are associated with reduced auxin efflux.
    J. Plant Physiol. (IF 2.825) Pub Date : 2005-07-13
    Bakul Rani Debi,Tory Chhun,Shin Taketa,Seiji Tsurumi,Kai Xia,Akio Miyao,Hirohiko Hirochika,Masahiko Ichii

    The phytohormone auxin is involved in the regulation of a variety of developmental processes. In this report, we describe how the processes of lateral root and root hair formations and root gravity response in rice are controlled by auxin. We use a rice mutant aem1 (auxin efflux mutant) because the mutant is defective in these characters. The aem1 line was originally isolated as a short lateral root mutant, but we found that the mutant has a defect in auxin efflux in roots. The acropetal and basipetal indole-3-acetic acid (IAA) transports were reduced in aem1 roots compared to wild type (WT). Furthermore, gravitropic bending as well as efflux of radioactive IAA was impaired in the mutant roots. We also propose a unique distribution of endogenous IAA in aem1 roots. An immunoassay revealed a 4-fold-endogenous IAA content in the aem1 roots compared to WT, and the application of IAA to the shoot of WT seedlings mimicked the short lateral root phenotype of aem1, suggesting that the high content of IAA in aem1 roots impaired the elongation of lateral roots. However, the high level of IAA in aem1 roots contradicts the auxin requirement for root hair formation in the epidermis of mutant roots. Since the reduced development in root hairs of aem1 roots was rescued by exogenous auxin, the auxin level in the epidermis is likely to be sub-optimum in aem1 roots. This discrepancy can be solved by the ideas that IAA level is higher in the stele and lower in the epidermis of aem1 roots compared to WT and that the unique distribution of IAA in aem1 roots is induced by the defect in auxin efflux. All these results suggest that AEM1 may encode a component of auxin efflux carrier in rice and that the defects in lateral roots, root hair formation and root gravity response in aem1 mutant are due to the altered auxin efflux in roots.

    更新日期:2019-11-01
  • Chlorophyll accumulation is enhanced by osmotic stress in graminaceous chlorophyllic cells.
    J. Plant Physiol. (IF 2.825) Pub Date : 2005-07-13
    Xóchitl García-Valenzuela,Edmundo Garcá-Moya,Quintín Rascón-Cruz,Luis Herrera-Estrella,Gerardo Armando Aguado-Santacruz

    We have developed a new chlorophyllic cell line ('TADH-XO') from the highly water stress tolerant grass Bouteloua gracilis (blue grama). When grown under normal (non-stress) conditions, this new cell line accumulates higher levels of chlorophyll (up to 368.1 microg total chlorophyll g(-1) FW) than a previously obtained cell line ('TIANSJ98'). Both cell lines are capable of developing substantially higher amounts of chlorophyll when subjected to osmotic stress. In order to explain these changes in the chlorophyll kinetics of the chlorophyllic cells, we analyzed the following population variables in cells subjected to polyethylene glycol 8000-induced osmotic stress: growth, viability, chlorophyll (total, 'a' and 'b'), cell size, percentage of green cells and chloroplast (number and size). Although previous studies in some chlorophyllic cells of dicots have already reported that chlorophyll increases under saline stress, in this report we show that, at least in this graminaceous cell line, the increase in chlorophyll is an immediate and proportional response to the osmotic stress applied and not the result of a progressive adaptation process. Consistent with previous studies, the increase in chlorophyll accumulation could be the result of chloroplast development (increased thylakoid number per chloroplast). On the basis of our results, the increases in chlorophyll accumulation previously observed in salt-adapted dicot cells may be the result of the osmotic shock (water deficit), rather than the ionic effect of salt on the physiology of chlorophyllic cells of dicots. Under the cell population experimental approach we followed, our study provides important insights related to the physiological behavior of chlorophyllic cells subjected to osmotic stress.

    更新日期:2019-11-01
  • Moderation of morphogenetic and oxidative stress responses in flax in vitro cultures by hydroxynonenal and desferrioxamine.
    J. Plant Physiol. (IF 2.825) Pub Date : 2005-06-09
    Bohus Obert,Erica E Benson,Steve Millam,Anna Pret'ová,David H Bremner

    Hypocotyl segments of 7-day old seedlings of flax (Linum usitatissimum L.) cultivars Atalante, Flanders, Jitka, Szegedi 30 and Super were screened for organogenesis (shoot and root induction) and embryo-like structure production. A non-destructive assay for hydroxyl radicals (*OH), utilising DMSO as a radical trap, was used to determine *OH formation during tissue culture and morphogenesis. Desferrioxamine, an inhibitor of Fenton reaction, and 4-hydroxy-2-nonenal, a cytotoxic Lipid peroxidation product, were exogenously applied to flax cultures to determine the effect of antioxidative and prooxidative status on morphogenetic responses induced through the exogenous application of plant growth regulators. Flax genotypes varied in their response to treatments after exposure to different plant hormones. Hydroxyl radical (*OH) formation correlated with morphogenetic responses and this was affected by plant hormones. Desferrioxamine and 4-hydroxy-2-nonenal also moderated morphogenetic responses and influenced hydroxyl radical formation during in vitro propagation.

    更新日期:2019-11-01
  • Carotenoid composition and its chemotaxonomic significance in leaves of ten species of the genus Ceratozamia (Cycads).
    J. Plant Physiol. (IF 2.825) Pub Date : 2005-06-09
    Franco Cardinif,Laura Morassi Bonzi

    The qualitative composition and localization of carotenoids in leaflets of ten species of the genus Ceratozamia (Cycads) was investigated, and the distributions of 16 of these carotenoids, which were isolated and differently located in the chloroplast, are discussed. Eight classic carotenoids are located in the thylakoidal membranes of the chloroplasts of all ten of the species examined. In contrast, eight red keto-carotenoids are unusually located in several plastoglobules present in the stroma of nine species Ceratozamia mexicana Brongn. excluded. The characteristic red-brown transitory coloration shown by the newly formed leaflets during the first stages of development is due to this latter keto mixture. It is constituted of three very rare keto-carotenoids, which were, in our case, identified for the first time from the photosynthetic tissues (semi-beta-carotenone, triphasiaxanthin, and beta-carotenone). It is also constituted of four others, which are completely novel (ceratoxanthin, ceratozamiaxanthin, kuesteriaxanthin, and ceratoxanthone). Some hypotheses about their presence and function are presented.

    更新日期:2019-11-01
  • Sap flow, gas exchange, and hydraulic conductance of young apricot trees growing under a shading net and different water supplies.
    J. Plant Physiol. (IF 2.825) Pub Date : 2005-05-20
    Emilio Nicolás,Arturo Torrecillas,José Dell'Amico,Juan José Alarcón

    The experiment was carried out in a research field near Murcia, Spain, over a 3-week period between September 26 and October 16, 2000. Sixteen trees were used in the experiment, eight of which were placed under a rectangular shading net, while the other eight were maintained in the open air. Trees were irrigated once per day and, after October 5th, water was witheld from eight trees (four shaded and four unprotected for 5 days). The leaf stomatal conductance and the photosynthesis rates were higher in the shaded trees than in the exposed plants, probably because the leaf water potential was lower in the unshaded plants. This higher leaf conductance partially compensated for the effect of low radiation on transpiration, and the reduction of daily sap flow registered in shaded trees was only around 10-20%. The net also affected trunk diameter changes, with the shaded trees showing lower values of maximum daily shrinkage. Soil water deficit and high radiation had a similar effect on plant water parameters, lowering leaf water potential, leaf stomatal conductance, and the photosynthesis rate. The effects of both conditions were accumulative and so the exposed water-stressed plants showed the lowest values of total hydraulic resistance and water use efficiency, while the shaded well-irrigated trees registered the highest values for both parameters. For this reason, we think that net shading could be extended to apricot culture in many areas in which irrigation water is scarce and insolation is high.

    更新日期:2019-11-01
  • Water deficit induced oxidative damage in tea (Camellia sinensis) plants.
    J. Plant Physiol. (IF 2.825) Pub Date : 2005-05-20
    Pavanasam Rajamanickam Jeyaramrajaa,Subramaniam Nithya Meenakshi,Raman Sasi Kumar,Sarvottam D Joshi,Balakrishan Ramasubramanian

    When the tea (Camellia sinensis) leaf water potential was -1.1 MPa (Moderate water deficit), there was 58% inhibition of photosynthesis accompanied by increased zeaxanthin, malondialdehyde, oxidized proteins and superoxide dismutase activity. When the leaf water potential was -2MPa (severe water deficit), there was nearly complete inhibition of photosynthesis apart from a decrease in chlorophylls, beta-carotene, neoxanthin and lutein. Water deficit at this level caused further conversion of violaxanthin to zeaxanthin, suggesting damage to the photosynthetic apparatus. There were consistent decreases in antioxidants and pyridine nucleotides, and accumulation of catalytic Fe, malondialdehyde and oxidized proteins. It is inferred that, in tea plants, the increase in catalytic Fe and the decrease in antioxidant protection may be involved in the oxidative damage caused by severe water deficit, but not necessarily in the incipient stress induced by moderate water deficit.

    更新日期:2019-11-01
  • Monitoring the stability of Rubisco in micropropagated grapevine (Vitis vinifera L.) by two-dimensional electrophoresis.
    J. Plant Physiol. (IF 2.825) Pub Date : 2005-05-20
    Luísa C Carvalho,Maria G Esquível,Isabel Martins,C Pinto Ricardo,Sara Amâncio

    Plants cultured in vitro suffer from several physiological and biochemical impairments due to the artificial conditions of growth, namely the composition of the heterotrophic media. Upon transfer to ex vitro, the higher irradiances, compared to in vitro, can lead to oxidative stress symptoms, which can be counteracted by CO2 concentrations above atmospheric levels. Here we analyse the stability of Rubisco in in vitro grapevine plantlets, and after transfer to ex vitro under four acclimatization treatments: low irradiance (LL, 150 micromol m(-2)s(-1)) and high irradiance (HL, 300 micromol m(-2)s(-1)) in association with CO2 concentrations of 350 (LCO2) and 700 (HCO2) microL L(-1). Proteins were separated with SDS polyacrylamide gel electrophoresis and two-dimensional electrophoresis and Rubisco degradation peptides were analysed by immunoblotting with anti-LSU antibodies. These degradation products were present in the leaves of plantlets under both in vitro and ex vitro treatments. Under LCO2 they were maintained for almost all of the 28 days of the acclimatization period, while becoming scarcely detected after 14 days under HCO2 and after 7 days when HCO2 was associated with HL. These results appear to confirm the counteraction of HCO2 concentrations over the oxidative stress eventually caused by HL. The patterns of soluble sugars in acclimatizing leaves under HLHCO2 also gave an indication of a faster acquisition of autotrophic characteristics.

    更新日期:2019-11-01
  • Hyperhydricity in shoot cultures of Scrophularia yoshimurae can be effectively reduced by ventilation of culture vessels.
    J. Plant Physiol. (IF 2.825) Pub Date : 2005-04-19
    Chien-Chou Lai,Hong-Ming Lin,Satish Manohar Nalawade,Wei Fang,Hsin-Sheng Tsay

    An effective procedure for obtaining healthy shoots from nodal segments of Scrophularia yoshimurae is described. Nodal segments cultured on Murashige and Skoog's (MS) basal medium supplemented with 1.0 mg L(-1) benzyladenine (BA) and 0.2 mg L(-1) alpha-naphthaleneacetic acid (NAA) induced multiple shoots in conical flasks that differed in the way they were closed and sealed. Hermitically sealed culture vessels resulted in high hyperhydricity/vitrification. High concentrations of ethylene and CO2 were found to accumulate in these vessels. The hyperhydricity of the shoot cultures could be decreased by progressively ventilating the vessels. Exchange of gases was achieved by removing the Parafilm sealing without affecting sterility. This reduced the hyperhydricity rate and gave a good recovery of vitrified shoots, but resulted in decreased proliferation and a dehydration of proliferating nodal segments and the culture medium. The best number of normal shoots was observed when the parafilm was removed for gaseous exchange after four weeks of culture incubation. The results show that hyperhydricity in shoot cultures of S. yoshimurae could be prevented by sufficient gas exchange during culture.

    更新日期:2019-11-01
  • High temperature effects on photosynthetic activity of two tomato cultivars with different heat susceptibility.
    J. Plant Physiol. (IF 2.825) Pub Date : 2005-04-19
    Daymi Camejo,Pedro Rodríguez,Ma Angeles Morales,José Miguel Dell'Amico,Arturo Torrecillas,Juan José Alarcón

    The functional activities of the photosynthetic apparatus of two tomato cultivars of different thermotolerance were investigated after a short period of high temperature treatment. Seedlings of two tomato genotypes, Lycopersicon esculentum var. Campbell-28 and the wild thermotolerant Nagcarlang, were grown under a photoperiod of 16h at 25 degrees C and dark period of 8h at 20 degrees C. At the fourth true leaf stage, a group of plants was exposed to heat stress of 45 degrees C for 2 h. The heat shock treatment caused important reductions of the net photosynthetic rate (Pn) of Campbell-28 plants due to non-stomatal components. These non-stomatal effects were not evident in Nagcarlang-treated plants. This reduction in the CO2 assimilation rate observed in Campbell-28 was generated by affections in the Calvin cycle and also in the PSII functioning. No changes in these parameters were observed in the thermotolerant genotype after the stress. Injury to the plasma membrane because of the heat stress was evident only in the Campbell-28 genotype. Heat led to a sun-type adaptation response of the photosynthesis pigment apparatus for the Nagcarlang genotype, but not for Campbell-28, and thus an increase in chlorophyll a/b ratio and a decrease in chlorophyll/carotenoid ratio were shown in Nagcarlang stressed plants.

    更新日期:2019-11-01
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