番茄低温响应转录因子NAC4的功能鉴定及调控机理研究

NAC转录因子在调控植物生长发育及非生物逆境应答中发挥着重要作用。前期，我们发现低温胁迫下一新的NAC转录因子基因（NAC4）在多毛番茄和普通番茄中差异表达，且多毛番茄ShNAC4与普通番茄SlNAC4在氨基酸序列上差异较大。初步分析表明，超量表达ShNAC4转基因植株矮化，难直立，对低温更敏感。共表达分析表明NAC4同果胶甲酯酶及ACC合成酶具有相似的表达模式。我们推测NAC4可能通过调控细胞壁发育和/或乙烯生物合成负调控番茄的抗寒性。为进一步阐明NAC4在番茄生长发育、低温应答中的功能及其调控机制，揭示ShNAC4和SlNAC4序列的差异是否会导致二者分子及生物学功能的不同，本项目将对ShNAC4和SlNAC4的表达模式、亚细胞定位、转录激活活性、在低温应答、细胞壁发育、乙烯生物合成中的功能及调控机制进行比较分析，并在此基础上，进一步探究细胞壁发育、乙烯生物合成与植株抗寒性之间的关系。

NAC transcription factors play vital roles in regulating plant growth and developmental processes as well as in response to abiotic stresses. In our previous study, a novel NAC transcription factor gene, NAC4 was differentially expressed between Solanum habrochaites and S.lycopersicum under cold stress, and there were some obvious differences in the deduced amino acid sequences of ShNAC4 and SlNAC4. Preliminary functional analysis indicated that the ShNAC4 overexpression transgenic plants were dwarf, unable to stand erect, and hypersensitive to cold stress as compared with the non-transgenic plants. Co-expression analysis showed that the expression of NAC4 is highly correlated with pectin methylesterase and ACC synthase gene. We surmised that NAC4 may negatively regulate cold tolerance by regulating cell wall development and/or ethylene biosynthesis in tomato. To further elucidate the function and regulatory mechanism of NAC4 in growth and development, and cold stress response in tomato, and reveal whether the differences in sequence between ShNAC4 and SlNAC4 would lead to a change in molecular and biological functions, the expression patterns, subcellular localization, transcriptional activation, the functions and regulatory mechanisms of ShNAC4 and SlNAC4 in response to cold stress, cell wall development，and ethylene biosynthesis will be compared and analyzed. Based on these, the relationship between cell wall development, ethylene biosynthesis, and cold tolerance will be further explored in this study.