Transcriptome analysis of Chongyi wild mandarin, a wild species more cold-tolerant than Poncirus trifoliata, reveals key pathways in response to cold
Introduction
Low temperature, either chilling (0–15 °C) or freezing (< 0 °C), is one of the major stressors limiting plant growth, development, yield and geographic distribution (Ji et al., 2019). A period of exposure to low but non-freezing temperatures could increase the tolerance of various temperate plants to subsequent freezing temperatures, which was defined as the process of cold acclimation (Thomashow, 1999). Besides decreasing temperature, the initiation of cold acclimation also needs decreasing photoperiod and changes in light quality (Chang et al., 2021). To date, many researches have been done and tremendous progresses have been made in dissecting the mechanism of cold acclimation and cold tolerance in plants (Baier et al., 2019; Ming et al., 2020; Prerostova et al., 2021). Cold-induced changes in membrane fluidity and rearrangement of the cytoskeleton might trigger the Ca2+ influx, which initiated the signal perception involving receptors such as calmodulin, Ca2+-dependent protein kinases (CPKs) and calcineurin B-like protein-interacting protein kinase 3 (CIPK3) (Kudla et al., 2018). Mitogen-activated protein kinase (MPKs) cascades and phytohormones, like abscisic acid (ABA), brassinosteroids (BRs), played important roles in the following cold signal transduction process (Li et al., 2017; Liu et al., 2020). Subsequently, an array of transcription factors (TFs) was activated and they regulated the expression of downstream cold regulated (COR) genes (Liu et al., 2014).
C-repeat binding factors (CBFs) play important roles in the cold-responsive pathway, which is also known as the dehydration-responsive element-binding factors (DREBs) and belonged to the APETALA2/ethylene-responsive factor-type transcription factor family (Fowler and Thomashow, 2002). CBFs can regulate the expression of a subset of COR genes encoding functional proteins like low-molecular-weight compatible osmolytes and reactive oxygen species (ROS)-scavenging proteins (Peng et al., 2014; Lv et al., 2020). The expression of CBFs was regulated by some upstream transcription factors, including inducer of CBF expression 1 (ICE1), MdBBX37, MdMYB88/MdMYB124, zinc finger of Arabidopsis thaliana 12 (ZAT12), ethylene-insensitive 3 (EIN3), brassinazole-resistant 1 (BZR1) and calmodulin binding transcription activators (CAMTA) (An et al., 2020; Doherty et al., 2009; Fowler et al., 2005; Huang et al., 2015; Kim et al., 2013; Li et al., 2017; Shi et al., 2012; Xie et al., 2018). On the post-translational level, the receptor-like cytoplasmic kinase cold-responsive protein kinase 1 (CRPK1) can phosphorylate 14-3-3 proteins and facilitate their binding with CBFs, leading to the proteasome-mediated degradation of CBFs (Liu et al., 2017). In addition, some CBF-independent genes were also reported, such as high expression of osmotically responsive gene 9, WKRY6, suppressor of overexpression of constans 1 (SOC1) (Zhu et al., 2004). Most of the above-mentioned investigations were done in Arabidopsis, while the cold responsive mechanism in non-model woody plants was less explored, especially in wild germplasms.
Citrus originated in Southeast Asia and spread worldwide with human activities, which has been one of the most economically important fruit crops (Liu, 1983; Zhu et al., 2019). China is considered as one of the centers of origin for the genus Citrus L. and rich in wild citrus germplasms, such as Ichang papeda (C. ichangensis), Hongkong kumquat (Fortunella hindsii), precocious trifoliate orange (Poncirus trifoliata), C. junos Sieb. ex Tanaka (Zhang et al., 2016; Wang et al., 2018). Wild mandarins were mostly distributed in a region around the Nanling Mountains in the south of China, such as Mangshan Mountain, Daoxian and Jiangyong Counties in Hunan Province, Chongyi County in the south of Jiangxi Province and Hezhou in the Guangxi Zhuang Autonomous Region (Nie and Hu, 1987; Li et al., 2007). Since commercial cultivars are vulnerable to various biotic and abiotic stresses due to the very narrow genetic diversity, wild germplasms have been considered as the ideal materials for genetic improvement of citrus (Wu et al., 2014). Therefore, the assessment of these wild citrus species resistant to various stresses is of great significance.
In 1977, a loose-skin mandarin (Citrus reticulata) was first discovered in the valleys of Chongyi County, locally called ‘Chou Gan’ in Chinese, meaning ‘smelly tangerine’ (Luo, 1981). But its evaluation and utilization has been rare. P. trifoliata was the commonly recognized citrus species with remarkable cold hardiness after a period of acclimation (Peng et al., 2020; Wang et al., 2019). Our preliminary experiments revealed that Chongyi wild mandarin had lower electrolyte leakage (EL) and malondialdehyde (MDA) content than P. trifoliata did after cold treatment, indicating that it might be more cold-tolerant. Therefore, we validated the cold tolerance of Chongyi wild mandarin using the membership function value method and analyzed its transcriptomic alteration in response to cold stress, which may contribute to the genetic improvement of cold-tolerant citrus cultivars in future.
Section snippets
Plant materials and cold treatment
Two-year-old trifoliate orange (Poncirus trifoliata (L.) Raf.) and Chongyi wild mandarin (Citrus reticulata Blanco) seedlings were collected in the nursery of National Navel Orange Engineering Research Center at Gannan Normal University. In late May, the 15–20 cm long shoots from the two plant materials were detached and placed in the ddH2O containing 0.1 % (w/v) NaCl to avoid freezing during 0 °C treatment. After being pre-cultured under ambient condition for 1 d, the detached shoots were
Chongyi wild mandarin showed less membrane damages than Poncirus trifoliata did
Electrolyte leakage (EL) and malondialdehyde (MDA) contents of the leaves from P. trifoliata and Chongyi wild mandarin after 0 °C treatment were measured and compared. As shown in Fig. 1, EL and MDA contents were increasing as the treatment continued, and the two indexes of Chongyi wild mandarin at each sampling point were significantly lower than that of P. trifoliata (P < 0.05/0.01/0.001). In addition, compared with the sharp elevation of EL in P. trifoliata after 3 d, EL in Chongyi wild
Discussion
P. trifoliata was used as an ideal rootstock in Citrus industry and a cold-hardy material in fundamental research (Dahro et al., 2016; Ming et al., 2020). In the present work, we reported a more cold-hardy wild citrus germplasm, Chongyi wild mandarin. Elucidation of its physiological and molecular mechanisms in response to cold will be of great significance.
Conclusion
In summary, we demonstrated the physiological and transcriptional alterations of a cold-hardy citrus germplasm, Chongyi wild mandarin, in response to cold. A corresponding working model was proposed in Fig. 11. Those common cold signaling pathways were triggered in Chongyi wild mandarin as in Arabidopsis and other plants, including Ca2+, MPKs, ABA, ethylene, but BR cascade probably played the dominant role. On the transcriptional level, a large quantity of TFs participated in the cold response
Funding
This work was supported by the National Natural Science Foundation of China (31760563) and National College Students Innovation and Entrepreneurship Training Program (201910418006).
CRediT authorship contribution statement
Ting Peng: Conceptualization, Funding acquisition, Supervision, Writing - original draft, Writing - review & editing. Xiao-Shang You: Methodology, Investigation, Validation, Formal analysis. Li Guo: Funding acquisition, Writing - review & editing. Ba-Lian Zhong: Resources, Investigation. Lan-Fang Mi: Methodology, Formal analysis. Jian-Mei Chen: Resources, Validation. Xuan Xiao: Writing - original draft, Writing - review & editing.
Declaration of Competing Interest
The authors report no declarations of interest.
References (64)
- et al.
Evaluation of 14 morphological, yield-related and physiological traits as indicators of drought tolerance in Chinese winter bread wheat revealed by analysis of the membership function value of drought tolerance (MFVD)
Field Crops Res.
(2012) - et al.
Whole-plant live imaging of reactive oxygen species
Mol. Plant
(2019) - et al.
De novo transcriptome sequencing and gene expression profiling of sweet potato leaves during low temperature stress and recovery
Gene
(2019) - et al.
Comparison of CBF1, CBF2, CBF3 and CBF4 expression in some grapevine cultivars and species under cold stress
Sci. Hortic.
(2015) - et al.
BZR1 positively regulates freezing tolerance via CBF-dependent and CBF-independent pathways in Arabidopsis
Mol. Plant
(2017) - et al.
Overexpression of an AP2/ERF family gene, BpERF13, in birch enhances cold tolerance through upregulating CBF genes and mitigating reactive oxygen species
Plant Sci.
(2020) - et al.
SERKing coreceptors for receptors
Trends Plant Sci.
(2016) - et al.
Gain- and loss-of-function mutations in Zat10 enhance the tolerance of plants to abiotic stress
FEBS Lett.
(2006) - et al.
Regulation of the Arabidopsis GSK3-like kinase RASSINOSTEROID-INSENSITIVE 2 through proteasome-mediated protein degradation
Mol. Plant
(2008) - et al.
Hormonal responses associated with acclimation to freezing stress in Lolium perenne
Environ. Exp. Bot.
(2021)
The zinc-finger protein Zat12 is required for cytosolic ascorbate peroxidase 1 expression during oxidative stress in Arabidopsis
J. Biol. Chem.
Molecular regulation of CBF signaling in cold acclimation
Trends Plant Sci.
Genome of wild mandarin and domestication history of mandarin
Mol. Plant
ABA-dependent and ABA-independent signaling in response to osmotic stress in plants
Curr. Opin. Plant Biol.
The cold-inducible CBF1 factor-dependent signaling pathway modulates the accumulation of the growth-repressing DELLA proteins via its effect on gibberellin metabolism
Plant Cell
Apple B-box protein BBX37 regulates jasmonic acid mediated cold tolerance through the JAZ-BBX37-ICE1-CBF pathway and undergoes MIEL1-mediated ubiquitination and degradation
New Phytol.
Preparing plants for improved cold tolerance by priming
Plant Cell Environ.
GSK3-like kinases positively modulate abscisic acid signaling through phosphorylating subgroup III SnRK2s in Arabidopsis
Proc. Natl. Acad. Sci. U. S. A.
Champions of winter survival: cold acclimation and molecular regulation of cold hardiness in evergreen conifers
New Phytol.
Sucrose efflux mediated by SWEET proteins as a key step for phloem transport
Science
PtrA/NINV, an alkaline/neutral invertase gene of Poncirus trifoliata, confers enhanced tolerance to multiple abiotic stresses by modulating ROS levels and maintaining photosynthetic efficiency
BMC Plant Biol.
The zinc-finger protein Zat12 plays a central role in reactive oxygen and abiotic stress signaling in Arabidopsis
Plant Physiol.
Roles for Arabidopsis CAMTA transcription factors in cold-regulated gene expression and freezing tolerance
Plant Cell
MYB30 orchestrates systemic reactive oxygen signaling and plant acclimation
Plant Physiol.
Arabidopsis transcriptome profiling indicates that multiple regulatory pathways are activated during cold acclimation in addition to the CBF cold response pathway
Plant Cell
Low temperature induction of Arabidopsis CBF1, 2, and 3 is gated by the circadian clock
Plant Physiol.
BRASSINOSTEROID INSENSITIVE2 interacts with ABSCISIC ACID INSENSITIVE5 to mediate the antagonism of brassinosteroids to abscisic acid during seed germination in Arabidopsis
Plant Cell
ICE1 of Pyrus ussuriensis functions in cold tolerance by enhancing PuDREBa transcriptional levels through interacting with PuHHP1
Sci. Rep.
ROS-driven oxidative modification: its impact on chloroplasts-nucleus communication
Front. Plant Sci.
Roles of CAMTA transcription factors and salicylic acid in configuring the low-temperature transcriptome and freezing tolerance of Arabidopsis
Plant J.
Advances and current challenges in calcium signaling
New Phytol.
Diversity, classification and function of the plant protein kinase superfamily
Philos. Trans. R. Soc. Lond. B Biol. Sci.
Cited by (8)
Transcriptome analysis reveals key metabolic pathways and gene expression involving in cell wall polysaccharides-disassembling and postharvest fruit softening in custard apple (Annona squamosa L.)
2023, International Journal of Biological MacromoleculesPhytohormones and Cold Stress Tolerance
2023, Plant Hormones and Climate ChangeTranscriptomic analysis reveals mechanisms for the different drought tolerance of sweet potatoes
2023, Frontiers in Plant Science
- 1
These authors contributed equally to this work.