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Freezing stress is one of the main factors limiting the growth and yield of wheat. In this study, we found that TaMYB4 expression was significantly upregulated in the tillering nodes of the strong cold-resistant winter wheat variety Dongnongdongmai1 (Dn1) under freezing stress. Weighted gene co-expression network analysis, qRT-PCR and protein–DNA interaction experiments demonstrated that monodehydroascorbate reductase (TaMDHAR) is a direct target of TaMYB4. The results showed that overexpression of TaMYB4 enhanced the freezing tolerance of transgenic Arabidopsis. In TaMYB4 overexpression lines (OE-TaMYB4), AtMDHAR2 expression was upregulated and ascorbate-glutathione (AsA–GSH) cycle operation was enhanced. In addition, the expression of cold stress marker genes such as AtCBF1, AtCBF2, AtCBF3, AtCOR15A, AtCOR47, AtKIN1 and AtRD29A in OE-TaMYB4 lines was significantly upregulated. Therefore, TaMYB4 may increase freezing tolerance as a transcription factor (TF) in Arabidopsis through the AsA–GSH cycle and DREB/CBF signaling pathway. This study provides a potential gene for molecular breeding against freezing stress. [ABSTRACT FROM AUTHOR]

The basic leucine zipper (bZIP) regulates plant growth and responds to stress as a key transcription factor of the Abscisic acid (ABA) signaling pathway. In this study, TabZIP genes were identified in wheat and the gene structure, physicochemical properties, cis-acting elements, and gene collinearity were analyzed. RNA-Seq and qRT-PCR analysis showed that ABA and abiotic stress induced most TabZIP genes expression. The ectopic expression of TaABI5 up-regulated the expression of several cold-responsive genes in Arabidopsis. Physiological indexes of seedlings of different lines under freezing stress showed that TaABI5 enhanced the freezing tolerance of plants. Subcellular localization showed that TaABI5 is localized in the nucleus. Furthermore, TaABI5 physically interacted with cold-resistant transcription factor TaICE1 in yeast two-hybrid system. In conclusion, this study identified and analyzed members of the TabZIP gene family in wheat. It proved for the first time that the gene TaABI5 affected the cold tolerance of transgenic plants and was convenient for us to understand the cold resistance molecular mechanism of TaABI5. These results will provide a new inspiration for further study on improving plant abiotic stress resistance. [ABSTRACT FROM AUTHOR]

Mitogen-activated protein kinases (MAPKs) play important roles in plant stress response. As a major member of the MAPK family, MPK3 has been reported to participate in the regulation of chilling stress. However, the regulatory function of wheat (Triticum aestivum ) mitogen-activated protein kinase TaMPK3 in freezing tolerance remains unknown. Dongnongdongmai No.1 (Dn1) is a winter wheat variety with strong freezing tolerance; therefore, it is important to explore the mechanisms underlying this tolerance. In this study, the expression of TaMPK3 in Dn1 was detected under low temperature and hormone treatment. Gene cloning, bioinformatics and subcellular localisation analyses of TaMPK3 in Dn1 were performed. Overexpressed TaMPK3 in Arabidopsis thaliana was obtained, and freezing tolerance phenotype observations, physiological indices and expression levels of ICE-C-repeat binding factor (CBF)-COR -related genes were determined. In addition, the interaction between TaMPK3 and TaICE41 proteins was detected. We found that TaMPK3 expression responds to low temperatures and hormones, and the TaMPK3 protein is localised in the cytoplasm and nucleus. Overexpression of TaMPK3 in Arabidopsis significantly improves freezing tolerance. TaMPK3 interacts with the TaICE41 protein. In conclusion, TaMPK3 is involved in regulating the ICE-CBF-COR cold resistance module through its interaction with TaICE41, thereby improving freezing tolerance in Dn1 wheat.

Dongnongdongmai No.1 (Dn1) is one of the few winter wheat varieties that can successfully overwinter at temperatures as low as -25°C or even lower. To date, few researches were carried to identify the freeze tolerance genes in Dn1 and applied them to improve plant resistance to extreme low temperatures. The basic helix-loop-helix (bHLH) transcription factor MYC2 is a master regulator in JA signaling, which has been reported to involve in responses to mild cold stress (2°C and 7°C). We hypothesized that MYC2 might be part of the regulatory network responsible for the tolerance of Dn1 to extreme freezing temperatures. In this study, we showed that wheat MYC2 ( TaMYC2 ) was induced under both extreme low temperature (-10°C and-25°C) and JA treatments. The ICE-CBF-COR transcriptional cascade, an evolutionary conserved cold resistance pathway downstream of MYC2, was also activated in extreme low temperatures. We further showed that overexpression of any of the MYC2 genes from Dn1 TaMYC2A, B, D in Arabidopsis led to enhanced freeze tolerance. The TaMYC2 overexpression lines had less electrolyte leakage and lower malondialdehyde (MDA) content, and an increase in proline content, an increases antioxidant defences, and the enhanced expression of ICE-CBF-COR module under the freezing temperature. We further verified that TaMYC2 might function through physical interaction with TaICE41 and TaJAZ7, and that TaJAZ7 physically interacts with TaICE41. These results elucidate the molecular mechanism by which TaMYC2 regulates cold tolerance and lay the foundation for future studies to improve cold tolerance in plants., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Wang, Yu, Xia, Xing, Fan, Xu, Cang and Zhang.)