In order to identify the genetic variations in root system architecture traits and their probable association with high- and low-affinity nitrate transport system, we performed several experiments on a genetically diverse set of wheat genotypes grown under two external nitrogen levels (optimum and limited nitrate conditions) at two growth points of the seedling stage. Further, we also examined the nitrate uptake and its transport under different combinations of nitrate availability in the external media using 15N-labelled N-source (15NO3−), and gene expression pattern of different high- and low-affinity nitrate transporters. We observed that nitrate starvation invariably increases the total root size in all genotypes. However, the variation of component traits of total root size under nitrate starvation is genotype-specific at both stages. Further, we also observed genotypic variation in both nitrate uptake and translocation depending on the growth stage, external nitrate concentration and growing conditions. The expression of the TaNRT2.1 gene was invariably up-regulated under low external nitrate concentration; however, it gets reduced after a longer period (21 days) of starvation than the early stage (14 days). Among the four NRT1.1 orthologs, TaNPF6.3 and TaNPF6.4 consistently showed higher expression than TaNPF6.1 and TaNPF6.2 at higher nitrate concentration at both the growth stages. TaNPF6.3 and TaNPF6.4 apparently showed a feature of typical low-affinity nitrate transporter gene at higher external nitrate concentration at 14 and 21 growth stages, respectively. The present study reveals the complex root system of wheat that has genotype-specific N-foraging along with highly coordinated high- and low-affinity nitrate transport systems for nitrate uptake and transport.

Triazole fungicides have been used for seed treatment to control soilborne diseases of maize, but seedlings coming from triazole-coated seed show serious phytotoxicity under chilling stress. To understand this phytotoxic impact, maize seed was treated with four triazoles fungicides and the corresponding seedlings were analysed on growth and gene expression. We found that maize seed coated with difenoconazole and tebuconazole exhibited either no or increased effects on germination and growth of maize at 25 °C, regardless of chemical concentrations. When maize seedlings were subjected to chilling treatment, however, their growth was significantly inhibited, and the inhibition was positively correlated with the rate of triazole application. Mesocotyl length decreased by 32.19–44.73% by difenoconazole, and 23.53–32.08% by tebuconazolet at rates of 1:50 and 1:25, respectively. However, myclobutanil did not have any effects at any temperatures. The contents of the gibberellin GA12 and abscisic acid in maize seedlings developed from difenoconazole- or tebuconazole-coated seed were significantly increased under chilling stress. The expression of two key catabolic enzyme genes, GA2ox3 and GA2ox4, was significantly up-regulated immediately following chilling stress and 2 days after recovery at 25 °C in the seedlings treated with difenoconazole or tebuconazole. This imbalance in phytohormones may explain why difenoconazole- or tebuconazole-coated seed more likely results in the phytotoxicity of maize seedlings under a low temperature condition during seed emergence and seedling growth. Since myclobutanil did not have this negative effect, it can be applied for seed coating in areas where temperatures are low during early seedling growth.

High temperatures and water-deficit stress limit cotton production around the world. Their individual effects on plant physiology and metabolism have been extensively studied, however, their combination has received considerably less attention. To that end, growth chamber experiments were conducted using cotton (Gossypium hirsutum L.) cultivar ST5288B2F and the objectives were to discern physiological and metabolic alterations after heat and water stress application (single or combined) and recovery, during cotton's vegetative stage. Under water stress conditions, leaf physiological parameters were suppressed and changes in carbohydrate levels, due to alterations in sucrose-metabolizing enzymes activities, were observed. Heat stress alone increased carbohydrate content, and activities of sucrose-degrading enzymes, while leaf physiology remained unaffected. The combined stress did exacerbate decreases in leaf water potential and soluble acid invertase activity, but the rest of the responses were similar to those of water stress. After stress alleviation, leaf physiological parameters of water-stressed plants did not manage to recover and substantial decreases were observed in leaf starch levels and activities of sucrose-cleaving enzymes, while the majority of parameters of heat-shocked plants returned to control levels. Recovery of the plants subjected to the combined stress was comparable to that of water-stressed plants, but significant differences were observed in carbohydrate levels and sucrose synthase activity. Our study demonstrated that under combined stress and post-stress conditions, water stress was the dominant factor affecting cotton leaf physiology and sucrose metabolism, highlighting however, the unique responses of some traits that could not be deduced from the additive effects of the single stresses.

In pepper crops, rootstocks that tolerate salt stress are not used because available commercial rootstocks offer limited profits. In this context, we obtained the hybrid NIBER®, a new salinity-tolerant rootstock that has been tested under real salinity field conditions for 3 years with 32%–80% higher yields than ungrafted pepper plants. This study aimed to set up the initial mechanisms involved in the salinity tolerance of grafted pepper plants using NIBER® as a rootstock to study root-shoot behavior, a basic requirement to develop efficient rootstocks. Gas exchange, Na+/K+, antioxidant capacity, nitrate reductase activity, ABA, proline, H2O2, phenols, MDA concentration and biomass were measured in ungrafted plants of cultivar Adige (A), self-grafted (A/A), grafted onto NIBER® (A/N) and reciprocal grafted plants (N/A), all exposed to 0 mM and 70 mM NaCl over a 10-day period. Salinity significantly and quickly decreased photosynthesis, stomatal conductance and nitrate reductase activity, but to lower extent in A/N plants compared to A, A/A and N/A. A/N plants showed decreases in the Na+/K+ ratio, ABA content and lipid peroxidation activity. This oxidative damage alleviation in A/N was probably due to an enhanced H2O2 level that activates antioxidant capacity to cope salinity stress, and acts as a signal molecule rather than a damaging one by contributing a major increase in phenols and, to a lesser extent, in proline concentration. These traits led to a minor impact on biomass in A/N plants under salinity conditions. Only the plants with the NIBER® rootstock controlled the scion by modulating responses to salinity.

Citrus greening, also called Huanglongbing (HLB), is one of the most destructive citrus diseases worldwide. It is caused by the fastidious gram-negative α-proteobacteria bacterium Candidatus Liberibacter asiaticus (CLas) and vectored by the Asian citrus psyllid (ACP), Diaphorina citri. Currently, there is no cure for HLB, no compounds have been successful in controlling HLB, and no sustainable management practices have been established for the disease. Thus, searching for alternative citrus greening disease mitigation strategies is considered an urgent priority for a sustainable citrus industry. The aim of this study was to use compounds extracted from oak, Quercus hemisphaerica, and to assess the antibacterial effects of these against CLas-infected citrus plants. The application of aqueous oak leaf extracts showed substantial inhibitory effects against CLas in citrus plants and the activity of genes related to starch. Significant differences were also observed in plant phenotypic and physiological traits after treatments. Citrus plants treated with oak extracts displayed an increase in stomatal conductance, chlorophyll content and nutrient uptake concurrently with a reduction of CLas titer, when compared to citrus plants treated with just water. The information provided from this study suggests a new management treatment program to effectively deal with the HLB disease.

Dendrobium officinale is an economically important Chinese herb with ornamental and medicinal values. However, the mechanisms by which D. officinale adapts to cadmium (Cd) stress is unknown. Here, physiological changes in D. officinale roots and leaves exposed to increasing levels of Cd stress (CdSO4 concentration of 2, 5, 9, 14 mg L−1) were analyzed at 7, 15, 30, and 45 days after treatment. The Cd stress of 14 mg L−1 significantly increased the levels of antioxidants and induced malondialdehyde and proline accumulation (P < 0.05). Cd subcellular distribution showed that Cd sequestration into soluble fraction is the major detoxification mechanism in D. officinale roots. Subsequently, the transcriptome profile of D. officinale roots treated with 14 mg L−1 Cd for 15 and 30 days was analyzed. Compared to control, 2,469 differentially expressed genes (DEGs) were identified, comprising 1,486 up-regulated genes and 983 down-regulated genes. The DEGs associated with metabolic pathways for Cd uptake, transportation and detoxification were analyzed. Several processes such as metal transporter, sulfate glutathione metabolism, cell wall metabolism, phenylpropanoid metabolism were identified to be important for Cd stress adaptation. More genes were expressed at 15 days after treatment compared to 30 days. WRKY, Trihelix, NF-YC, MYB, bZIP and bHLH transcription factors were over-expressed at both time points. Furthermore, candidate genes from the glutathione metabolism pathway were identified, and qRT-PCR analysis of ten DEGs indicated a high coorelation with RNA-seq expression profiles. Our findings provide significant information for further research of Cd stress responsive genes functions in D. officinale, especially the genes from the glutathione metabolism pathway.

Trivalent aluminum ions (Al3+) in acidic soils are a major constraint for crop productivity inhibiting root elongation and promoting cell death. Al3+-toxicity has adverse biochemical and physiological effects on plant root growth. Sulfur is an essential macronutrient assimilated from the soil in the form of sulfate. However, the implication of sulfate nutritional status in the modulation of short-term Al3+-tolerance mechanisms in plant roots has not been previously reported. Here, we evaluated the effects of increased sulfate supply on short-term Al3+-toxicity in roots of Lolium perenne, measuring Al, Ca, Mg and S uptake, lipid peroxidation, total SOD activity, and transcriptional levels of Cu/Zn and Fe-SOD genes. First, the nitrogen sulfur ratio (N/S) in the TF nutrient solutions used in this study were computed to confirm that L. perenne plants were grown in sulfate deficiency (120 μM), optimal supply (240 μM), or overdoses conditions (360 μM), without affecting dry root biomass. Sulfate supplementation (>240 μM, and N/S ratio < 16) played a significant protection to Al3+-stress that prevents morphological changes in root tips, inhibits lipid peroxidation and differentially up-regulates total SOD activity, due changes in SOD gene expression. The results support the importance of sulfate nutritional status, on plant tissue homeostasis, enhancing the physiological tolerance mechanisms modulating lipid peroxidation damage induced by short-term Al3+-toxicity.

The cupuassu tree (Theobroma grandiflorum) is a crop of great economic importance to Brazil, mainly for its pulp and seeds, which are used in food industry. However, cupuassu fruit production is threatened by witches' broom disease caused by the fungus Moniliophthora perniciosa. As elements of its defense mechanisms, the plant can produce and accumulate pathogenesis-related (PR) proteins such as chitinases and osmotins. Here, we identified three PR proteins from cupuassu (TgPR3, TgPR5 and TgPR8) from cupuassu-M. perniciosa RNA-seq data. TgPR3 and TgPR8 corresponded to chitinases, and TgPR5 to osmotin; they are phylogenetically related to cacao and to Arabidopsis PR sequences involved in biotic and abiotic stress. The TgPR proteins' tridimensional structure was obtained through homology modeling, and molecular docking with chitin and chitosan showed that the TgPR proteins can interact with both cell wall molecules and presented a higher affinity for chitosan. TgPR gene expression was analyzed by RT-qPCR on resistant and susceptible cupuassu genotypes infected by M. perniciosa at 8, 24, 48 and 72 h after infection (hai). The TgPR genes showed higher expression in resistant plants compared to the susceptible ones, mainly for TgPR5 at 8 and 24 hai, while the expression was lower in the susceptible cupuassu plants. To our knowledge, this is the first in silico and in vitro reports of cupuassu PR protein. The data suggested that TgPRs could be involved in recognizing mechanisms of the plant's innate immune system through chitin receptors. Our results also suggest a putative role of chitinase/chitosanase for the TgPR5/osmotin.

Drought is a major environmental factor limiting crop growth and development worldwide. WRKY transcription factor, a unique transcription factor in plants, has been shown to play important roles in plant response to abiotic stress. Previously, we have cloned the VvWRKY13 gene from resistant grape varieties and found that its expression was obviously induced by drought. Here we further explored the mechanism of VvWRKY13 in response to drought stress. After drought treatment, the expression of VvWRKY13 in the sensitive grape variety was significantly higher than resistant grape varieties. Moreover, phenotypic changes of VvWRKY13 transgenic Arabidopsis were observed and drought-related indexes were detected under drought treatment. The results showed that VvWRKY13 transgenic Arabidopsis exhibited more sensitive phenotype to drought stress compared with wild type. The water loss rate of leaves in the transgenic Arabidopsis was significantly higher than wild type. The content of proline, soluble sugar and the expression of related genes decreased in transgenic Arabidopsis leaves under drought stress. The level of endogenous hydrogen peroxide and oxygen free radicals was increased, while the activity of catalase (CAT) and superoxide dismutase enzyme (SOD) were decreased. In addition, the expression of stress response gene was significantly decreased in transgenic Arabidopsis. Taken together, our results suggest that VvWRKY13 negatively modulates plant drought tolerance through regulating the metabolism of intracellular osmotic substances (proline, soluble sugar), the level of ROS, and the expression of stress-related genes.

Stevia rebaudiana Bert. is getting global attention because of its ability to synthesize commercially important low/no calorie natural sweeteners (LNCSs) steviol glycosides (SGs). Considering, higher accumulation of SGs in vegetative phase followed by decrement during reproductive phase necessitate the understanding of different molecular components of floral transition to develop superior varieties/cultivars with prolonged vegetative phase in Stevia. Current comparative transcriptional analysis of low dose (5 kR) gamma-irradiated mutant genotype (SMG) with prolonged vegetative phase vis-à-vis background genotype (SBG) identified DGEs of major floral transition pathways, and expressed according to their physiological fate irrespective to SMG & SBG. Contrarily, reduced expression of floral integrator genes (FT and LEAFY) in mutant genotype suggests their involvement in prolonged vegetative phase phenotype. Likewise, GO and KEGG enrichment of photosynthesis and carbon assimilation efficiency might be associated with prolonged vegetative phase and higher accumulation of Stevioside content in mutant genotype. Furthermore, deviation of flowering related transcription factors (higher expressions except MIKS-type MADS-box SMG_PV compared to SBG_F) may possibly be correlated with low expression of floral integrator genes. Findings of current studies will facilitate the genetic manipulations and crop improvement efforts in Stevia through conventional breeding and genome editing approaches for increased SGs biosynthesis.

Secondary metabolites (SMs) of medicinal plants are the material basis of their clinically curative effects. They are also important indicators for evaluating the quality of medicinal materials. However, the synthesis and accumulation of SMs are very complex, which are affected by many factors including internal developmental genetic circuits (regulated gene, enzyme) and by external environment factors (light, temperature, water, salinity, etc.). Currently, lots of literatures focused on the effect of environmental factors on the synthesis and accumulation of SMs of medicinal plants, the effect of the developmental growth and genetic factors on the synthesis and accumulation of SMs still lack systematic classification and summary. Here, we have given the review base on our previous works on the morphological development of medicinal plants and their secondary metabolites, and systematically outlined the literature reports how different environmental factors affected the synthesis and accumulation of SMs. The results of our reviews can know how developmental and environmental factors qualitatively and quantitatively influence SMs of medicinal plants and how these can be integrated as tools to quality control, as well as on the improvement of clinical curative effects by altering their genomes, and/or growth conditions.

Proper storage prolongs peony market supply. Here, we determined the changes in fresh weight and expression of four aquaporin genes under dry storage (DS) and wet storage (WS). It has showed that after harvesting, the fresh weight change was accompanied with flower opening. After both short- and long-term of storage, the water uptake efficiency in DS group was greater during the first few vase days, providing a direct material basis of DS improved vase quality. The gene expression results showed that PlPIP1;3 and PlTIP2;1 were mainly expressed in petals, whereas PlNIP1;2-like and PlSIP2;1 were mainly expressed in the green tissues. In addition, the expression of PlTIP2;1 in the petals was consistent with the flower opening process, indicating that it may play a major role in facilitating water uptake. During cold storage, the expression of PlPIP1;3 and PlTIP2;1 was higher or more rapidly induced in the DS group, and thus we deduced that they play important roles in improving the vase quality of DS. Furthermore, the expression of PlNIP1;2-like in the early stage of the DS group was more stable than in WS, which may also be partially responsible for the vase quality improvement. In contrast, PlSIP2;1 may not be involved, since no significant change was observed between the DS and WS group. In short, the expression of PlPIP1;3 and PlTIP2;1 in the DS group during storage may improve water uptake efficiency during the vase period and then improving the vase quality of cut peony.

For the purpose of the current study, hairy root induction in S. bornmuelleri, which is an important medicinal plant, was examined using a particular protocol. Accordingly, some factors such as four strain types of Agrobacterium rhizogenes (A4, A3, MSU440 and ATCC15834), three different explants, namely stem, petiole and leaf, two co-cultivation media, i.e. full and half-MS were studied. Besides, two inoculation methods including injection and immersion as well as three inoculation times (5, 7 and 10 min) were closely taken into account. Utilizing injection method by MSU440 strain, hairy root induction took place in stem explants, and a remarkable increase in transformation frequency (100%) was observed in half-strength MS medium. Methyl jasmonate (MeJA, 100 μM), methyl-b-cyclodextrin (b-CD, 0.7, 7 and 14 mM) and Chitosan (Chi, 50, 100 and 200 mg/l) were used either individually or in a combined way to elicitation. Based on the HPLC results, production of chrysin, wogonin and baicalein increased 9.15, 10.56 and 13.25 times after elicitation of hairy roots by MeJA + Chi. In addition, transcripts of FNSП2 and MYB7, two important genes involved in the flavonoid biosynthesis pathway, were studies. By applying Chi and MeJA + Chi elicitor, the expression of both genes increased noticeably. It can be concluded that the mentioned hairy root culture system of S. bornmuelleri can be an alternative to flavonoids production. Moreover, there is a direct and positive relationship between the expression of FNSП2 and MYB7 genes as well as the level of three flavonoids.

SrUGT76G1 is vital for the biosynthesis of rebaudioside A, D and M in Stevia rebaudiana Bertoni; however, its transcriptional regulatory mechanism remains unknown. In this study, the 2,050-bp promoter region of SrUGT76G1 was isolated by the TAIL-PCR method, and sequence analysis revealed the presence of several W-box cis-elements, which are the recognition motifs of WRKY transcription factors. Furthermore, SrWRKY71, characterized by a typical WRKY domain and a C2H2 zinc finger-like motif, was identified as a putative transcriptional regulator of SrUGT76G1. The transcript of SrWRKY71 predominantly accumulated in leaves and was present at a lower level in stems, roots and flowers. The SrWRKY71-GFP fusion protein was specifically localized to the nucleus in tobacco epidermal cells. In addition, the N and C terminal regions of SrWRKY71 contributed to its transactivation activity. Y1H and EMSA assays validated that SrWRKY71 binds directly to W-box1 and W-box2 in the proximal promoter region of SrUGT76G1. Moreover, SrWRKY71 represses the expression level of SrUGT76G1 in both tobacco leaves and stevia callus. Taken together, the data in this study represent the first identification of an essential upstream transcription factor of SrUGT76G1 and provides new insight into the regulatory network of steviol glycoside biosynthesis in Stevia rebaudiana.

In order to evaluate the genes involved in polyamines synthesis pathway and the role of nitric oxide synthase (NOS) and H2O2 in stomatal closure under drought stress, a research conducted with three irrigation levels (100, 50 and 25% field capacity) at 1, 3, 6 and 12 days on Rosa damascena Mill. HPLC and qPCR results showed that putrescine (Put) accumulation occurred at first day in both 50% and 25% of field capacity and then decreased the other days. Furthermore, Put accumulation in the indirect pathway (ADC, AIH and CPA) was more effective related to the direct pathway (ODC) under severe stress. Increased expression of genes involved in production of spermidine (Spd) and spermine (Spm) i.e., SAMDC, SPDS and SPMS correlated with the highest accumulation of Spd and Spm under 50% FC at 6 d and 25% FC at 12 d, respectively. Moreover, results showed that Put reduction simultaneously accumulated H2O2, which subsequently increased NOS expression suggesting a key signal for stomatal closure.

Abscisic acid (ABA) is a ubiquitous phytohormone, plays important roles in several physiological processes, including stress adaptation, flowering, seed germination, fruit ripening, and leaf senescence etc. ABA binds with START domain proteins called Pyrabactin Resistance1 (PYR1)/PYR1-like (PYL)/Regulatory Components of ABA Receptors (RCARs) and controls the activity of PP2C phosphatase proteins and in turn the ABA-dependent signaling pathway. Fourteen ABA receptors have been identified in the model plant Arabidopsis thaliana and have shown to be involved in various biological functions. Under field conditions, exogenous application of ABA produces inadequate physiological response due to its rapid conversion into the biologically inactive metabolites. ABA shows selective binding preferences to PYL receptor subtypes and hence produces pleiotropic physiological and phenotypic effects which limit the usage of ABA in agriculture. An agrochemical meant for ameliorating the undesirable physiological effect of the plant should ideally have positive biological attributes without affecting the normal growth, development, and yield. Therefore, to overcome the limitations of ABA for its usage in various agricultural applications, several types of ABA-mimicking agents have been developed. Many compounds have been identified as having significant ABA-agonist/antagonist activity and can be employed to reverse the excessive/moderate ABA action. The present review highlights the potential usage of ABA signaling modulators for managing agronomic and postharvest traits. Besides, designing, development and versatile usage of ABA-mimicking compounds displaying ABA agonists and antagonist activities are discussed in detail.

Climate change would increase frequency and intensity of extreme events as heat and cold waves. There is a lack of studies that consider the co-occurrence of these waves with other abiotic factors relevant on a climate change scenario as salinity. Therefore, it could be interesting to improve our knowledge about the effects that this co-occurrence could have in different species due to the species specific effect of the photosynthesis tolerance to extreme temperatures. A controlled condition experiment was performed using the salt marsh species Sarcocornia perrnis with eight experimental blocks combining temperature ranges (40-28/22-15/13-5 °C) and salinity concentration on the growth solution (171/1050 mM NaCl). After 3 days of treatment, gas exchange, chlorophyll a fluorescence, pigment profile and water state measurement were applied. Photosynthetic machinery function of this perennial species decreased on for both high and low temperature range. Nevertheless, at 13-5 °C the effect of the salinity was mainly due to diffusion limitations more than to damage on the photosystems. At 40-28 °C, in presence of optimal salinity S. fruticosa was not altered overall. However, high temperatures in combination with high salinity reduced the photosynthetic capacity mainly by reducing the efficiency of the electron transport chain.

Salt stress limits crop productivity worldwide, particularly in arid and heavily irrigated regions. Salt stress causes oxidative stress, in which plant cells accumulate harmful levels of reactive oxygen species (ROS). Thioredoxins (Trxs; EC 1.8.4.8) are antioxidant proteins encoded by a ubiquitous multigene family. Arabidopsis thaliana Trx h-type proteins localize in the cytoplasm and other subcellular organelles, and function in plant responses to abiotic stresses and pathogen attack. Here, we isolated the Arabidopsis genes encoding two cytosolic h-type Trx proteins, AtTrx-h2 and AtTrx-h3 and generated transgenic oilseed rape (Brassica napus) plants overexpressing AtTrx-h2 or AtTrx-h3. Heterologous expression of AtTrx-h2 in B. napus conferred salt tolerance with plants grown on 50 mM NaCl having higher fresh weight and chlorophyll contents compared with controls in hydroponic growth system. By contrast, expression of AtTrx-h3 or the empty vector control did not improve salt tolerance. In addition, AtTrx-h2-overexpressing transgenic plants exhibited lower levels of hydrogen peroxide and higher activities of antioxidant enzymes including peroxidase, catalase, and superoxide dismutase, compared with the plants expressing the empty vector control or AtTrx-h3. These results suggest that AtTrx-h2 is a promising candidate for engineering or breeding crops with enhanced salt stress tolerance.

Stripe rust is a fungal disease that has devastated the barley production for a long time. The present study focused on the role of β-glucan, PR proteins, diamine oxidase (DAO), polyamine oxidase (PAO), key enzymes and metabolites of phenol and proline metabolism in the stripe rust resistance of barley. RD2901 with resistant behavior against stripe rust showed increased levels of PR proteins, phenylalanine ammonia lyase (PAL), tyrosine ammonia lyase (TAL) along with the accumulation of β-glucan and lignin which strengthen the plant cell wall during plant-pathogen interaction. It also depicted the enhanced activities of glutamate dehydrogenase (GDH) and ornithine aminotransferase (OAT) coupled with the increased amounts of proline, glycine betaine and choline after infection with M-race of P. striiformis f. sp. hordei. On the contrary, the sensitive genotype Jyoti was unable to enhance the activities of most of these enzymes except PAL and OAT so that it showed an increase in lignin and choline contents only. Secondly, the increase in lignin content was less as compared to the tolerant genotype. Hence, it can be inferred that these key metabolites and enzymes of various metabolic pathways may contribute to the resistance of barley against stripe rust pathogen. This study suggested that these key enzymes and their metabolites could serve as markers for the characterization of plant defensive state that is essential for crop protection.

The broad application and unique properties of graphene oxide (GO) nanosheets make them interact with other pollutants and subsequently alter their behaviors and toxicities. However, investigation on the effects of GO nanosheets on plant uptake of co-occurring heavy metals is scarce. We evaluated the mutual effects of cadmium (Cd) at 1 mg/L and different concentrated GO nanosheets (0, 1 and 10 mg/L) on the rice seed germination, further seedling growth, Cd uptake and accumulation in rice roots and shoots in a hydroponic system. The effects of GO were concentration dependent. GO alone at 1 mg/L showed no apparent effects, while GO alone at 10 mg/L accelerated the rice seed germination and root growth due to the improved water uptake. Cd alone showed adverse effects on the rice seed germination, which was alleviated by the presence of GO at 1 or 10 mg/L. GO at 10 mg/L also increased the membrane permeability, thus enhancing Cd uptake by rice roots and shoots. These results indicate that GO can change the effects of Cd on the rice seed germination and Cd uptake as well as accumulation in the roots and shoots of rice seedlings, which is helpful for understanding the fate and ecotoxicological impacts of both GO and Cd.

Cuticular wax is known to play an important role in non-stomatal transpiration. However, support is lacking regarding the waxy phenotype for wheat breeding against drought. In this study, four wheat cultivars with different wax phenotypes (glaucous and non-glaucous types) were used to evaluate their responses to drought stress and impact on photosynthetic capability of wheat. Xinong 291 and HY 2912, with the glaucous trait, demonstrated higher diketone ratios and contents compared with Pubing 201 and Jinmai 47, which are the non-glaucous type. The cultivars HY 2912 and Jinmai 47 had 35% higher biomass than did Xinong 291 and Pubing 201 under severe drought condition. HY 2912 exhibited the highest wax load with or without drought stress. Jinmai 47 showed the highest ratio of alkane content. Among glaucous cultivars, drought-resistant HY 2912 may promote growth by decreasing water loss, increasing the diketone content, increasing the total wax load, and maintaining mesophyll and stomatal conductance. Among non-glaucous cultivars, drought-resistant Jinmai 47 may enhance growth via stomatal closure and increased mesophyll conductance and alkane ratios. The glaucous trait was not always associated with drought resistance, and correlation analysis revealed that the diketone ratio was positively related to the intercellular CO2 concentration. These results suggest that the mechanism of drought resistance in wheat is systematically regulated by wax alteration, stomatal conductance and mesophyll conductance. Therefore, wax content and composition as well as mesophyll and stomatal regulation should be considered in the breeding and selection of drought-resistant wheat cultivars.

As one of the largest families of transcription factors in plants, the R2R3-MYB proteins play important roles in diverse biological processes including growth and development, primary and secondary metabolism such as flavonoid and anthocyanin biosynthesis as well as abiotic and biotic stress responses. However, functions of R2R3-MYB genes in rapeseed (Brassica napus L.) remain elusive. Here, we characterized BnaMYB111L, which is homologous to Arabidopsis MYB111 and encodes an R2R3-MYB protein in rapeseed. BnaMYB111L is responsive to abscisic acid (ABA), heat, cold, hydrogen peroxide and fungal pathogen Sclerotinia scelerotiorum treatments through quantitative RT-PCR assay. BnaMYB111L encodes a transcriptional activator and is localized exclusively to nuclei. Interestingly, overexpression of BnaMYB111L in tobacoo (Nicotiana benthamiana) and rapeseed protoplasts promoted reactive oxygen species (ROS) production and hypersensitive response-like cell death, accumulation of malondialdehyde (MDA) as well as degradation of chlorophyll. Furthermore, BnaMYB111L expression evoked the alterations of transcript levels of genes encoding ROS-producing enzyme, vacuolar processing enzymes and genes implicated in defense responses. A further dual luciferase reporter assay indicated that BnaMYB111L activated the expression of RbohB, MC4 and ACRE132, which are involved in ROS generation, cell death as well as defense responses. Taken together, this study characterized the function of rapeseed MYB111L and identified its putative target genes involved in ROS production and cell death.

Cotton (Gossypium hirsutum) is an important cash crop, providing people with high quality natural fiber. Lignin is the main component of cotton fiber, second only to cellulose. As a main substance filled in the cellulose framework during the secondary wall thickening process, lignin plays a key role in the formation of cotton fiber quality. However, the mechanism behind it is still unclear. In this research, we screened candidate genes involved in lignin biosynthesis based on analysis of cotton genome and transcriptome sequence data. The authenticity of the transcriptome data was verified by qRT-PCR assay. Total 62 genes were identified from nine gene families. In the process, we found the key gene GhCAD7 that affects the biosynthesis of S-lignin and the ratio of syringyl/guaiacyl (S/G). In addition, in combination with the metabolites and transcriptome profiles of the line 0–153 with high fiber quality and the line sGK9708 with low fiber quality during cotton fiber development, we speculate that the ratio of syringyl/guaiacyl (S/G) is inseparable from the quality of cotton fiber. Finally, the S-type lignin synthesis branch may play a more important role in the formation of high-quality fiber. This work provides insights into the synthesis of lignin in cotton and lays the foundation for future research into improving fiber quality.

Virus-induced gene silencing (VIGS) is a technology for rapid gene functional analysis that depends on the degradation of viral RNA and is part of the natural defense mechanism in plants. Senecio cruentus is an important Compositae ornamental species that is plentiful and available in a variety of colors and has a typical blue variety that is rare in Compositae. These advantages make it a good material for studying the anthocyanin biosynthesis and blue flower formation mechanism. With the development of gene sequencing technology, the functions of many candidate genes that may be involved in anthocyanin biosynthesis in S. cruentus need to be identified. However, a stable and rapid genetic transformation system of S. cruentus is still lacking. Here, we screened two cultivars, ‘Venezia’ and ‘Jseter’, chosen ScPDS and ScANS as test genes, and investigate the effect of developmental periods, bacterial cell concentrations and infection methods on gene silencing efficiency. The results showed that the silencing efficiency of S. cruentus leaves was low (13%), and it was less affected by the parameters. However, the transcription factor gene ScbHLH17 was still silenced by VIGS, which resulted in the loss of anthocyanin accumulation in leaves, and the expression levels of anthocyanin biosynthesis pathway (ABP) structural genes, including ScCHI, ScDFR3 and ScANS, were decreased significantly. The result proved that ScbHLH17 was an important transcription factor that regulated flower color formation in S. cruentus. In addition, ScANS-silencing phenotypes were observed in S. cruentus capitulum by vacuum-infiltrating S1 stage buds for 10 min after scape injection. In general, the present study provided important technical support for the study of anthocyanin metabolism pathways in S. cruentus.

The increase in soil salinization due to global climate change could cause large losses in crop productivity affecting, among other biological processes, to germination and seedling development. We have studied how salt stress affects nucleic acid degrading activities in radicles of common bean during seedling development. In radicles of common bean, a main nuclease of 37 kDa and two ribonucleases of 17 and 19 kDa were detected. Saline stress did not alter these three activities but induced a new ribonuclease of 16 kDa. All three ribonucleases are acidic enzymes that were inhibited by Zn. The 16 and 17 kDa ribonucleases are inhibited by guanilates. In the genome of common bean, we have identified 13 genes belonging to the T2 ribonuclease family and that are grouped in the 3 classes of T2 ribonucleases. The analysis of the expression of the 3 genes belonging to Class I (PvRNS1 to 3) and the unique gene from Class II (PvRNS4) in radicles showed that PvRNS3 is highly induced under salt stress.

Ethylene-response factor (ERF) proteins are members of a transcription factor family involved in plant growth and environmental stress responses, but the biological functions of ERF members in adzuki bean (Vigna angularis var. angularis) remain unknown. In addition, it is unclear whether these proteins have a role in regulating responses to abiotic stressors. Here, we identified 47 ERF genes by analyzing the adzuki bean genome. Whole-transcriptome analyses of plants under saline-alkaline stress suggested that the expression of 13 ERF genes was induced in response to saline-alkaline stress. Analysis of the cis-acting elements showed that the promoters of these saline-alkaline stress-inducible ERF genes contained LTRs, DREs, MYBs, ABREs, MYCs, CGTCA-, and TGACG-motifs, which are involved in abiotic stress responses. The expression of VaERF3 was induced by NaHCO3, polyethylene glycol 6000, NaCl, and ABA (abscisic acid), as determined by qRT-PCR. Overexpression of VaERF3 in transgenic Arabidopsis resulted in higher levels of proline accumulation and lower malondialdehyde and reactive oxygen species contents in plants grown under saline-alkaline stress conditions. Moreover, VaERF3 encoded a nuclear-localized transcriptional activator that promoted the expression of stress-responsive genes. Collectively, these results are of great significance in elucidating the mechanisms of saline-alkaline stress responses in adzuki bean.

Plants that perform the Crassulacean acid metabolism (CAM), which obtain CO2 overnight and convert it mainly in malic acid, successfully grow in environments with water and nutrient shortages, that is partly associated with their higher water- and nitrogen-use efficiencies. Water and nutrient limitations can impair photosynthesis through the reduction of RuBisCO and increment of photorespiration, disturbing the plant carbon balance. In this context, we conducted a controlled experiment with the epiphytic C3-CAM bromeliad Guzmania monostachia to investigate how the combined water and nutritional deficits affect the activity of RuBisCO and its activation state (RAS), and to evaluate the efficiency of photosynthesis during the transition from C3 to CAM. Apart from an increase in CAM activity, bromeliads submitted to both water and nutritional deficits showed higher RAS values and unaltered RuBisCO activity compared to C3 bromeliads and, surprisingly, the maximum quantum efficiency of photosynthesis increased. Glucose, fructose and starch levels were maintained, while sucrose concentrations increased over time. These results, combined with the high RAS values, suggest an increased efficiency of RuBisCO functioning. Our results reinforce the ability of epiphytic bromeliads to deal with stressful habitats by a higher efficiency of RuBisCO during the transition to CAM, another feature that may allow their evolution in the epiphytic environment.

MicroRNA166 (miR166) contributes to post-transcriptional regulation by binding the mRNAs of HD-ZIP III genes, which affects plant growth and development. The structural characteristics, expression, and functions of miR166 genes during the early somatic embryogenesis stage in Dimocarpus longan remain unknown. We isolated the transcripts of pri-miR166 S78 with two transcription initiation sites (TSSs) and pri-miR166 S338 with one TSS. These sequences contain potential smORFs and encode different miRNA peptides (miPEPs). Additionally, their promoters contain cis-acting elements responsive to diverse stimuli. The pre-miR166 S78 and pre-miR166 S338 expression levels were up-regulated in response to 2,4-D, abscisic acid, and ethylene. Although the expression patterns induced by hormones were similar, there were differences in the extent of the response, with pre-miR166 S338 more responsive than pre-miR166 S78. Thus, miRNA transcription and maturation are not simply linearly correlated. Moreover, pre-miR166 S78 and pre-miR166 S338 expression levels were down-regulated, whereas ATHB15 (target gene) expression was up-regulated, from the longan embryonic callus to the globular embryo stages. These results are indicative of a negative regulatory relationship between miR166 and ATHB15 during the early somatic embryogenesis stage in longan. At the same stages, miR166a.2-agomir, miR166a.2-antagomir, and miPEP166 S338 increased or decreased the expression of miR166a.2 and ATHB15, but with no consistent patterns or linear synchronization, from which we've found some reasons for it.

Aquaporins (AQPs) transport water and other small molecules; however, their precise role in abiotic stress responses is not fully understood. In this study, we cloned and characterized the PIP2 group AQP gene, MaPIP2-7, in banana. MaPIP2-7 expression was upregulated after osmotic (mannitol), cold, and salt treatments. Overexpression of MaPIP2-7 in banana improved tolerance to multiple stresses such as drought, cold, and salt. MaPIP2-7 transgenic plants showed lower levels of malondialdehyde (MDA) and ion leakage (IL), but higher contents of chlorophyll, proline, soluble sugar, and abscisic acid (ABA) compared with wild type (WT) plants under stress and recovery conditions. Additionally, MaPIP2-7 overexpression decreased cellular contents of Na+ and K+ under salt and recovery conditions, and produced an elevated K+/Na+ ratio under recovery conditions. Finally, ABA biosynthetic and responsive genes exhibited higher expression levels in transgenic lines relative to WT under stress conditions. Taken together, our results demonstrate that MaPIP2-7 confers tolerance to drought, cold, and salt stresses by maintaining osmotic balance, reducing membrane injury, and improving ABA levels.

This study addressed the interactions between salt stress and the antioxidant responses of a halophytic grass, Desmostachya bipinnata. Plants were grown in a semi-hydroponic system and treated with different NaCl concentrations (0 mM, 100 mM, 400 mM) for a month. ROS degradation enzyme activities were stimulated by addition of NaCl. Synthesis of antioxidant compounds, such as phenols, was enhanced in the presence of NaCl leading to accumulation of these compounds under moderate salinity. However, when the ROS production rate exceeded the capacity of enzyme-controlled degradation, antioxidant compounds were consumed and oxidative damage was indicated by significant levels of hydrogen peroxide at high salinity. The cellular concentration of salicylic acid increased upon salt stress, but since no direct interaction with ROS was detected, a messenger function may be postulated. High salinity treatment caused a significant decrease of plant growth parameters, whereas treatment with moderate salinity resulted in optimal growth. The activity and abundance of superoxide dismutase (SOD) increased with salinity, but the abundance of SOD isoforms was differentially affected, depending on the NaCl concentration applied. Detoxification of hydrogen peroxide (H2O2) was executed by catalase and guaiacol peroxidase at moderate salinity, whereas the enzymes detoxifying H2O2 through the ascorbate/glutathione cycle dominated at high salinity. The redox status of glutathione was impaired at moderate salinity, whereas the levels of both ascorbate and glutathione significantly decreased only at high salinity. Apparently, the maximal activation of enzyme-controlled ROS degradation was insufficient in comparison to the ROS production at high salinity. As a result, ROS-induced damage could not be prevented, if the applied stress exceeded a critical value in D. bipinnata plants.

Oxidative stress induced by salinity is a prime cause of cell death when Na+ toxicity becomes unbearable. We explored the effect of rosmarinic acid (RA) on the Solanum tuberosum L. cv. Desiree calli against salt-induced programmed cell death (PCD). We showed that PCD events were triggered in calli under 250 mM NaCl by the loss of plasma membrane integrity as measured by the amount of malondialdehyde (MDA) in the cytoplasm, the degree of DNA degradation resulting from the cleavage of nuclear DNA into oligonucleosomal fragments in apoptotic cells, the presence of TUNEL-positive nuclei (90 ± 0.005%) damage in genomic DNA, and activation of caspase 3-like protease. Callus Formation Medium (CFM) supplemented with RA led to the suppression of salt-induced cell death and a dramatic decrease in the MDA level and frequency of TUNEL-positive nuclei under salinity to 4 ± and 7.3 ± % in the presence of 50 and 350 μM RA, respectively. The application of RA also resulted in an increase in GSH content and maintenance of a high GSH/GSSG ratio. Interestingly, these reductions in PCD were accompanied by inhibiting caspase 3-like protease activities due to RA under salinity. Molecular docking predicted high binding energies of RA for binding to subtilisin-like protease (StSCTc-3), which has caspase-3 like activity in Solanum tuberosum, near the active site. This finding supports the notion of a role for RA in PCD protection in plants, which is consistent with earlier reports in animal cells.

Release of bud dormancy is a prerequisite for the growth resumption and production in perennial plants such as tree peony. DNA methylation plays a pivotal role in regulating gene expression. In this study, combination of morphologic observation and DNA methylation analysis indicated that 5-azacytidine (5-azaC) application for 7 d declined 5 mC quantities and promoted dormancy release. After 5-azaC treatment, total 174,341 unigenes and 1,818 differentially expression genes (DEGs) were obtained by RNA-seq, of which there were 1,194 DEGs after 1 d 5-azaC treatment (AD1 vs CD1), and 624 DEGs after 7 d (AD7 vs CD7), respectively. The KEGG pathway analysis identified that totally 10 DEGs annotated in DNA replication pathway were enriched when AD7 compared with CD7. Furthermore, the expression patterns of several DEGs by real-time quantitative RT-PCR were consistent with that of RNA-seq data. 5-azaC application significantly decreased the expression levels of DNA methyltransferase genes, PsCMT3, PsMET1 and PsDRM2, and increased the transcript of demethylase gene PsROS1. Simultaneously, total methyltransferases activity decreased, and demethylase activity was induced by 5-azaC. In summary, application of 5-azaC inhibited the expression of the genes related to growth and development in short-term, indicating a possible toxic effect to plant, and its long-term effect was to induce hypomethylation by increasing demethylase genes transcripts and decreasing the expressions of methyltransferase genes, and then activate cell cycle, DNA replication and glycol-metabolism processes, which subsequently accelerated dormancy release. All these would provide a new strategy to further understand the molecular mechanism of dormancy release in tree peony.

Flavonoids are the most important secondary metabolites in ginkgo (Ginkgo biloba L.) leaves that determine its medicinal quality. Studies have suggested that secondary metabolism is strongly affected by temperature in other plant species, but little is known about ginkgo. In this study, we investigated the effects of different day-night temperature combinations (15/10, 25/20, and 35/30 °C (day/night)) on key enzyme activity, growth regulator concentrations, and flavonoid accumulation in ginkgo leaves. We found that phenylalanine ammonia-lyase (PAL) activity was enhanced and inhibited at 15/10 and 35/30 °C, respectively. Cinnamate-4-hydroxylase (C4H) activity was relatively stable under the three temperature conditions, and the p-coumarate CoA ligase (4CL) activity showed different trends under the three temperature conditions. The concentrations of flavonoid constituents (quercetin, kaempferol, and isorhamnetin) were decreased and increased under the 35/30 and 15/10 °C conditions, respectively. Low temperature promoted soluble sugar accumulation, while temperature had a limited impact on the accumulation of soluble protein. The pattern of change in the total flavonoid concentration was not always in agreement with PAL activity due to its complex pathway. Indoleacetic acid (IAA) and gibberellin (GA) changes shared similar patterns and had limited effects on flavonoid accumulation, while abscisic acid (ABA) acted as a promotor of flavonoid accumulation under high-temperature conditions. The total flavonoids achieved the highest content under the 15/10 °C treatment on the 40th day. Therefore, the lower temperature (15/10 °C) is more favorable for flavonoid accumulation and will provide a theoretical basis for further study.

An experimentation was carried out to appraise whether or not nitric oxide (NO) contributes to salicylic acid (SA)-induced salinity tolerance particularly by regulating ascorbate-glutathione (AsA-GSH) cycle. Before starting salinity stress (SS), SA (0.5 mM) was sprayed to the foliage of plants once every other day for a week and then seedlings were grown under control or SS (100 mM NaCl), for five weeks. Salinity stress enhanced the AsA-GSH cycle-related enzymes, glutathione reductase (GR), ascorbate peroxidase (APX), and dehydroascorbate reductase (DHAR), and monodehydroascorbate reductase (MDHAR). Furthermore, SS caused substantial decreases in plant physiological-related traits such as leaf potassium (K) contents, K+/Na+ ratio, the ratios of reduced ascorbate/dehydroascorbic acid (AsA/DHA) and reduced glutathione/oxidized glutathione (GSH/GSSG), but in contrast, significant increases occurred in leaf hydrogen peroxide, malondialdehyde, electron leakage, proline, the premier antioxidant enzymes’ activities, Na+ and NO. SA reduced leaf Na+ content and oxidative stress-related traits, but improved all earlier-mentioned traits compared with those in plants treated with SS alone. All positive effects of SA were eliminated by NO scavenger, 0.1 mM 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1- oxyl-3-oxide (c-PTIO) by reducing NO, suggesting that NO produced by SA up-regulated the activities of AsA-GSH cycle and antioxidant enzymes, so it could play a central function as a signal molecule in salt tolerance of pepper plants.

Programmed cell death (PCD) play essential roles in plant growth and development. Stigmatic papilla cells form an indispensable organ for plant reproduction. The lifetime of papilla cells is tightly controlled, and the developmental PCD (dPCD) process is involved in papilla cell death. Hence, papilla cell death is a good model for studying on PCD process. In this study, the dPCD signal was visualized in dying papilla cells by detecting the GUS signal of the PCD-related reporter gene BIFUNCTIONAL NUCLEASE 1 (BFN1). We found that the GUS was not expressed at young stage, but strongly expressed in papilla cells at the ageing stage, indicating the PCD process was triggered to terminate the papilla cell fate. Given this, the RNA-Seq data set, which covered the information of the whole lifespan of papilla cells, was analyzed aiming to understand which genes and pathways were involved in papilla cell death. 37 differential expressed genes (DEGs) were isolated. Moreover, the pathways related to energy production and transportation, autophagy, and plant hormone signal transduction were considered as the key pathways involved in the papilla cell death. 9 types, total of 104 transcriptional factors (TFs) were identified as well. Finally, a putative working model of papilla cell death was integrated. The findings herein will enrich the knowledge of the dPCD-mediated pathway in regulating plant organ/tissue growth, development, senescence, and death. Our study will provide some referential gene resources for studying on the dPCD in other plant organs or tissues.

Ultraviolet (UV)–B priming can boost the abiotic stress tolerance of plants by activating stress-responsive pathways. The main objective of the present study was to investigate the persistence of priming imprints and cross-tolerance inducing effects of UV-B priming in abiotic stress-sensitive rice (Oryza sativa L. ‘Aiswarya’) when subjected to various abiotic stressors (NaCl, PEG, and UV-B). The UV-B priming of rice seeds and seedlings effectively enhanced photosynthetic efficiency, antioxidant machinery activity, and antioxidative enzyme production, especially when seedlings were exposed to NaCl, followed by UV-B and PEG. The ability of UV-B priming to induce cross-tolerance against NaCl stress was substantiated by the greater antioxidant activity of the primed and NaCl-stressed seedlings. The greater performance and stress tolerance of the seedlings from UV-B-primed seeds were attributed to the carryover of priming imprints from seeds into the seedlings. Indeed, UV-B priming activated the antioxidant systems of the seedlings, even under non-stress conditions, and resulted in greater responses upon subsequent stress exposure, which suggested that preparedness for encountering imminent stress was attained by UV-B priming in a stress-sensitive rice.

Salinity stress reduces growth and yield productivity of most crop plants. Potentiality of kinetin (Kn) and epi-brassinolide (EBL), either individually or combinedly in preventing the salinity (100 mM NaCl) stress mediated oxidative damage and photosynthetic inhibition was studied in Solanum lycopersicum. Combined application of Kn and EBL imparted much prominent impact on the growth, photosynthesis and metabolism of antioxidants, osmolytes and secondary metabolites. Synthesis of chlorophylls and carotenoids increased and the photosynthetic parameters like stomatal conductance, intercellular CO2 concentration and net photosynthesis were significantly improved due to application of Kn and EBL. Photosystem II functioning (Fv/Fm), photochemical quenching and electron transport rate (ETR) improved significantly in Kn and EBL treated plants imparting significant decline in salinity induced non-photochemical quenching. Exogenous Kn and EBL effectively prevented the oxidative damage by significantly declining the generation of hydrogen peroxide and superoxide under saline and non-saline conditions as reflected in lowered lipid peroxidation and electrolyte leakage. Reduced oxidative damage in Kn and EBL treated plants was accompanied down-regulation of protease and lipoxygenase concomitant with up-regulation of the antioxidant system and the accumulation of compatible osmolytes. Treatment of Kn and EBL proved effective in enhancing the contents of redox homeostasis, ascorbic acid and reduced glutathione, and the secondary metabolites assisting the enzymatic antioxidant system in combating the salinity stress efficiently. Results suggest that combined application of Kn and EBL regulate growth and photosynthesis in tomato more effectively than their individual application through a probable regulatory crosstalk mechanism.

In an altitudinal Brazilian ecosystem, fog is a frequent event in both the dry and rainy seasons. The drought stress is aggravated in the dry season due to elevated evaporative demand and this constraint can induce oxidative stress in plants. In this ecosystem, there are plants which present different foliar water uptake (FWU) capacities - species that absorb less water more quickly (LQ) and those that absorb more water more slowly (MS). In this study, the relationship between oxidative stress responses and the different FWU strategies was evaluated in dry and rainy seasons. The oxidative stress was assessed by H2O2 production and lipid peroxidation as well as by the antioxidant enzymes system as superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX). During the dry season, plants had higher oxidative stress compared to rainy season plants which exhibited moderate oxidative damage. The FWU strategies were closely related to oxidative stress responses, since the LQ species presented the higher H2O2 content and oxidative defense system. Contrastingly, it was found that MS species have the lowest values of H2O2 and less SOD, CAT and APX activities. However, the lipid peroxidation did not present any relation with FWU strategies. Altogether results revealed that plants, which present MS strategy, are more adapted to cope with the higher H2O2 concentrations generated in the dry season and drought stress events than those that present LQ strategy.

The WRKY transcription factor family includes plant-specific transcription factors that are widely involved in plant biotic and abiotic stress responses, growth and development. Tartary buckwheat is a type of small grain with strong resistance to adverse growing conditions. No systematic exploration of the WRKY family in Tartary buckwheat has yet been reported. In this paper, we report the FtWRKY46 gene from Tartary buckwheat and study its role in salt tolerance. FtWRKY46 has transcriptional activation activity in yeast, and FtWRKY46 fused to yellow fluorescent protein localizes to the nucleus. Further studies have found that its transcriptional activation region is located at the N-terminus. A yeast one-hybrid assay indicated that FtWRKY46 could bind to a W-box and activate reporter gene expression. Similarly, transient cotransfection showed that FtWRKY46 could specifically bind to W-box regions and activate reporter gene expression in plants. Furthermore, ectopic expression of FtWRKY46 could enhance Arabidopsis tolerance to salt stress. More specifically, the seed germination rate, root length, chlorophyll content and proline content were significantly higher in transgenic plants ectopically expressing FtWRKY46 than in WT plants after salt stress (P < 0.05), while MDA levels were significantly lower than in WT plants (P < 0.05). Additionally, salt treatment increased the expression of stress-related genes. To summarize, our results suggest that ectopic expression of FtWRKY46 enhance the stress tolerance of transgenic plants by modulating ROS clearance and stress-related gene expression.

Saline-alkali stress is a major abiotic stress limiting plant growth. The selection of saline-alkali-tolerant rootstock is an effective strategy to reduce salinization-alkalization influence in apple production. M. halliana is a highly saline-alkali-resistant apple rootstock in northwestern China. However, few metabolic response studies have been conducted on this species. In plants under saline-alkali stress, the uptake of K, Mg and Zn in M. halliana leaves were inhibited, whereas the absorption of Fe2+, Cu2+ or Mn2+ were increased. Metabolic analysis revealed 140 differentially expressed metabolites, which were mainly involved in alkaloid biosynthesis, phenylalanine biosynthesis, ATP-binding cassette (ABC) transporters, and mineral absorption. Especially, the expression of sucrose, amino acids, alkaloids, flavonoids and carotenoids were significantly upregulated under saline-alkali stress. qRT-PCR analysis demonstrated that NHX8 and ZTP1 involved in Na+ and Fe2+ transport were upregulated, while AKT1, MRS2-4 and ZTP29 involved in K+, Mg2+ and Zn2+ transport were downregulated, respectively. ANT, ATP2A, CALM and SOS2 are involved in Ca2+ signal transduction, and ABCB1, ABCC10 and NatA are key transporters that maintain ionic homeostasis. M. halliana regulates Na+/K+ homeostasis by mediating Ca2+ signalling and ABC transporters. The accumulation of metabolites contributes to improving the saline-alkali resistance of M. halliana because of the scavenging of ROS. An increase in pheophorbide a content in porphyrin and chlorophyll metabolism leads to leaf senescence in M. halliana leaves, which contributes to a reduction in stress-induced injury. These findings provide important insights into the saline-alkali tolerance mechanism in apple, which also provides an important starting point for future research.

The ubiquitin/26S proteasome pathway is widely related to plant growth and metabolism and response to treatment by specifically degrading ubiquitin-modified proteins, including RING-finger-type E3 ubiquitin ligase (RING). The RING finger protein (RFP) gene family, determining the specificity of the ubiquitination process, is numerous and complex in function. In this study, we constructed a pCEGFP-StRFP2 fusion protein expression vector and transformed it into tobacco to achieve transient expression, thereby confirming that StRFP2 is localized in the cell membrane and cytoplasm. The result of qRT-PCR analysis showed that StRFP2 gene was significantly expressed in potato leaves, and the expression level of StRFP2 was significantly up-regulated under drought treatment. The transgenic plants of overexpressing StRFP2 gene were obtained with Agrobacterium tumefaciens-mediated transformation. Plant height, stem diameter, root length, fresh weight and root-shoot ratio of transgenic plants were significantly higher than those of non-transgenic plants (WT), indicating that the growth of plants was significantly promoted after overexpression of StRFP2 gene. Under PEG osmotic stress, the expressional level of StRFP2 in transgenic potato plants was significantly higher than that of WT. Furthermore, the free proline content and CAT activity in transgenic plants were higher than WT, on the contrary, MDA was lower than WT, and transgenic plants have stronger water retention capacity under simulated drought stress treatment, which indicated that StRFP2 could strengthen the tolerance of plants responding to drought stress. The above evidence strongly suggested that the StRFP2 gene is obviously up-regulated expression by drought stress, thereby enhancing the drought tolerance of the potato.

Invertase inhibitor (INH) post-translationally regulates the activity of invertase, which hydrolyzes sucrose into glucose and fructose, and plays essential roles in plant growth and development. However, little is known about the role of INH in growth and responses to environmental challenges in sweetpotato. Here, we identified and characterized an INH-like gene (IbINH) from sweetpotato. IbINH belongs to the pectin methylesterase inhibitor super family. IbINH transcript was the most abundant in storage roots. IbINH mRNA levels were significantly up-regulated in response to drought, abscisic acid (ABA), salicyclic acid (SA) and jasmonic acid (JA) treatments. Overexpressing IbINH in sweetpotato (SI plants) led to the decrease of plant growth and the increase of drought tolerance, while down-regulation of IbINH (RI plants) by RNAi technology resulted in vigorous growth and drought sensitivity. Furthermore, sucrose was increased and hexoses was decreased in SI plants, but the opposite results were observed in RI plants. Moreover, higher levels of sugars were accumulated in SI plants in comparison to non-transgenic plants (NT plants) and RI plants during water deficit. In addition, ABA biosynthesis-involved and abiotic stress response-involved genes were prominently up-regulated in SI plants under drought stress. Taken together, these results indicate that IbINH mediates plant growth and drought stress tolerance in sweetpotato via induction of source-sink strength and ABA-regulated pathway.

Copper-containing amine oxidases (CuAOs) catalyse polyamines (PAs) terminal oxidation producing ammonium, an aminoaldehyde and hydrogen peroxide (H2O2). Plant CuAOs are induced by stress-related hormones, methyl-jasmonate (MeJA), abscisic acid (ABA) and salicylic acid (SA). In the Arabidopsis genome, eight genes encoding CuAOs have been identified. Here, a comprehensive investigation of the expression pattern of four genes encoding AtCuAOs from the α and γ phylogenetic subfamilies, the two peroxisomal AtCuAOα2 (At1g31690) and AtCuAOα3 (At1g31710) and the two apoplastic AtCuAOγ1 (At1g62810) and AtCuAOγ2 (At3g43670), has been carried out by RT-qPCR and promoter::green fluorescent protein-β-glucuronidase fusion (GFP-GUS). Expression in hydathodes of new emerging leaves (AtCuAOγ1 and AtCuAOγ2) and/or cotyledons (AtCuAOα2, AtCuAOγ1 and AtCuAOγ2) as well as in vascular tissues of new emerging leaves and in cortical root cells at the division/elongation transition zone (AtCuAOγ1), columella cells (AtCuAOγ2) or hypocotyl and root (AtCuAOα3) was identified. Quantitative and tissue-specific gene expression analysis performed by RT-qPCR and GUS-staining in 5- and 7-day-old seedlings under stress conditions or after treatments with hormones or PAs, revealed that all four AtCuAOs were induced during dehydration recovery, wounding, treatment with indoleacetic acid (IAA) and putrescine (Put). AtCuAOα2, AtCuAOα3, AtCuAOγ1 and AtCuAOγ2 expression in vascular tissues and hydathodes involved in water supply and/or loss, along with a dehydration-recovery dependent gene expression, would suggest a role in water balance homeostasis. Moreover, occurrence in zones where an auxin maximum has been observed along with an IAA-induced alteration of expression profiles, support a role in tissue maturation and xylem differentiation events.

Chloroplast, the energy organelle unique to photosynthetic eukaryotes, executes several crucial functions including photosynthesis. While chloroplast development and function are controlled by the nucleus, environmental stress modulated alterations perceived by the chloroplasts are communicated to the nucleus via retrograde signaling. Notably, coordination of chloroplast and nuclear gene expression is synchronized by anterograde and retrograde signaling. The chloroplast proteome holds significance for stress responses and adaptation. We unraveled dehydration-induced alterations in the chloroplast proteome of a grain legume, chickpea and identified an array of dehydration-responsive proteins (DRPs) primarily involved in photosynthesis, carbohydrate metabolism and stress response. Notably, 12 DRPs were encoded by chloroplast genome, while the rest were nuclear-encoded. We observed a coordinated expression of different multi-subunit protein complexes viz., RuBisCo, photosystem II and cytochrome b6f, encoded by both chloroplast and nuclear genome. Comparison with previously reported stress-responsive chloroplast proteomes showed unique and overlapping components. Transcript abundance of several previously reported markers of retrograde signaling revealed relay of dehydration-elicited signaling events between chloroplasts and nucleus. Additionally, dehydration-triggered metabolic adjustments demonstrated alterations in carbohydrate and amino acid metabolism. This study offers a panoramic catalogue of dehydration-responsive signatures of chloroplast proteome and associated retrograde signaling events, and cellular metabolic reprograming.

DNA mismatch repair (MMR) is a highly conserved biological pathway that improves the fidelity of DNA replication and recombination. MMR is initiated when MutS proteins recognize mismatches and small loops of unpaired nucleotides. Arabidopsis thaliana and other plants encode MutS protein homologs (MSH) conserved among other eukaryotic organisms, but also encode an extra MSH polypeptide (MSH7). In order to better understand the role of MSH7 in vivo, a full set of phenotypic parameters that covered the development of the plant from seed imbibition to flowering and seed maturation were analyzed in A. thaliana harboring two different msh7 alleles. Plants deficient in MSH7 show statistically significant faster germination rates, longer primary roots during the juvenile vegetative phase, and higher cauline leaf and axillary and lateral inflorescence numbers compared with wild type. We also quantified number, length and area of siliques and seed number per silique. Disruption of MSH7 resulted in a higher number of smaller siliques than wild type. There were no differences in seed number per silique between genotypes. These findings suggest that mutant plant growth appears to be caused by an impaired cell cycle checkpoint that allows cell division without adequate DNA repair. This increase in proliferation activity demonstrates a functional and temporal link between DNA repair and cell cycle regulation.

Tea cultivars with leaf color variation have attracted increasing attention in tea production and research due to their unusual appearances and appealing flavors. However, the molecular mechanism underlying this variation is little known due to the unavailability of genetic transformation and a highly complex genome. Here, a natural tea plant mutant producing pale green branches (pgb) was discovered and characterized. Ultrastructural and biochemical analyses showed that the leaves of the pgb mutant had defective chloroplast structure and significantly lower pigment content than the normal control. Comprehensive expression detection of chloroplast-development-related genes further indicated that a significant downregulation of CsGLKs in the pgb mutant likely caused the chloroplast defect. Transcriptome analyses and polyphenolic compound determination highlighted a tight correlation between photosynthesis and secondary metabolite biosynthesis in tea plant. These results provide useful information illuminating the mechanism of chloroplast development and leaf color variation in tea plant.

Chrysanthemum [Dendranthema morifolium Tzvel.] is an ornamental plant grown under long-term artificial cultivation conditions. In production, early Chrysanthemum blossoms are often promoted by artificial short-day treatment. However, we found that the flower colour of Chrysanthemum blossoms induced by artificial short-day treatment was lighter than those induced by the natural photoperiod. To explore the intrinsic mechanism of colour fading in flowers, we performed full-length transcriptome sequencing of Chrysanthemum morifolium cv. ‘Jinbeidahong’ using single-molecule real-time sequencing and RNA-sequencing under natural daylight (ND) and short daylight (SD) conditions. The clustered transcriptome sequences were assigned to various databases, such as NCBI, Swiss-Prot, Gene Ontology and so on. The comparative results of digital gene expression analysis revealed that there were differentially expressed transcripts (DETs) in the four stages under ND and SD conditions. In addition, the expression patterns of anthocyanin biosynthesis structural genes were verified by quantitative real-time PCR. The major regulators of the light signalling ELONGATED HYPOCOTYL5 genes were markedly upregulated under ND conditions. The patterns of anthocyanin accumulation were consistent with the expression patterns of CHI1 and 3GT1. The results showed that the anthocyanin synthesis is tightly regulated by the photoperiod, which will be useful for molecular breeding of Chrysanthemum.

The involvement of wheat germ agglutinin (WGA) in the protective action of 24-epibrassinolide (EBR) against drought stress was studied in the seedling roots of two wheat cultivars differing in drought tolerance. Under dehydration conditions, the contents of ABA and WGA were shown to change significantly in the roots of either drought-tolerant cultivar Omskaya 35 or drought-sensitive cultivar Salavat Yulaev. Meanwhile, accumulation of either ABA or WGA started earlier and was two times greater in plants of drought-tolerant cultivar. Since WGA is an excreted protein, it is not surprising that the level of lectin in the roots gradually decreased by the 7th day of treatment due to its exudation into root environment. Pre-sowing treatment with EBR contributed to additional accumulation of lectin as compared to the control variants of either cultivar, while the hormone treatment did not change ABA content. Meanwhile, under conditions of drought, EBR-pretreated seedlings were characterized by lower level of accumulation of ABA and WGA in the roots. EBR application was found to prevent drought-induced inhibition of cell division in the root apical meristem, while WGA excreted into the root environment may contribute significantly to the effect.

The HD-ZIP Ⅳ transcription factors have been identified and functional characterized in many plant species. However, no tobacco HD-ZIP IV gene has been isolated, and it is not yet known whether HD-ZIP IV genes are involved in controlling flavonols accumulation in plants. Here, we cloned a HD ZIP gene named NtHDG2 from Nicotiana tabacum, which belongs to the class IV of HD-ZIP family, and the NtHDG2-GFP fusion protein is localized to the nucleus. We further observed that the flavonols contents in the NtHDG2 overexpression leaves increase to 1.9–4.5 folds of that in WT plants, but in the NtHDG2-RNAi plants the flavonols contents reduce to 20.9%–52.7% of that in WT plants. The transcriptions of one regulatory gene NtMYB12, and three structural genes (NtPAL, NtF3′H, NtF3GT), contributing to flavonols biosynthesis, were significantly induced by NtHDG2. However, the transcription level of NtNAC002, a flavonols biosynthesis repressor, was also significantly up-regulated in NtHDG2-overexpression lines, but significantly down-regulated in the RNAi lines, indicating that HDG2 regulates the synthesis of flavonols as a complex regulatory network. Moreover, ectopic expression of NtHDG2 gene promoted the transcription of several AP2/ERF genes, including NtERF1-5, NtERF109, NtDREB1, and NtCIPK11, which participate in regulating root development and resistance to abiotic stresses. Our findings reveal the new function of HD-ZIP IV transcription factors in flavonoids biosynthesis, and indicate that HD-ZIP IV members may play an important role in plant resistance to abiotic stress. The NtHDG2 gene provides a promising target for genetically manipulating to increase the amounts of flavonols in tobacco leaves.