生物钟转录抑制复合体 Evening Complex 调控茉莉酸诱导叶片衰老的分子机制研究

By initiating leaf senescence to cope with environmental stresses or to utilize the limited nutrients and energy for growth and reproduction, plants are able to relocate energy and nutrients from aging leaves to developing tissues or storage organs. Circadian clock regulates many biological processes of plants, however, whether it can regulate leaf senescence still await further exploring. The evening complex, comprised of ELF4 (EARLY FLOWERING 4), ELF3 (EARLY FLOWERING 3) and LUX (LUX ARRHYTHMO) proteins, play a crucial repressive role in core oscillator of circadian clock. But whether it involved in the regulation of jasmonate-induced leaf senescence and the potential underlying molecular mechanism still remain elusive. During our preliminary study, we found the mutants of evening complex components showed accelerated JA-induced leaf senescence, while ovexpression ELF3 reduced the JA-induced leaf senescence. In this project, we will aiming to decipher the underlying molecular mechanism of evening complex regulating JA-induced leaf senescence. We will systematically investigate JA-induced leaf senescence in evening complex component mutants and transgenic lines by utilizing the established physiological experiments. Moreover, we want to investigate which component of JA signaling pathway is the direct target of evening complex. In addition, we will try to establish the signaling module of ‘Evening complex-MYC2-SAG29-leaf senescence’ which mediates the cross talk between circadian clock and plant leaf senescence. Our research in this project will elucidate the related underlying molecular mechanisms of the clock and plant leaf senescence and lay the broad foundation for cross talk between circadian clock and JA signaling, which will be beneficial for future crop breeding.

植物启动叶片衰老过程促进营养和能量由源到库转移，提高植物对干旱等胁迫的耐逆性和存活率。生物钟在时间维度动态地调控着植物生长发育的多个方面，但对生物钟调控叶片衰老的研究还甚少。前期研究我们发现生物钟转录抑制复合体Evening Complex的相关突变体加速了茉莉酸诱导的叶片衰老过程，而超表达植株则减缓了此过程。本项目将深入研究Evening Complex调控茉莉酸诱导叶片衰老的分子机制。研究内容包括定性和定量分析Evening Complex相关材料对茉莉酸诱导叶片衰老的生理表型；发掘和定位Evening Complex调控茉莉酸信号途径的关键节点；利用分子生物学和遗传学手段确定MYC2为Evening Complex的靶基因，进而建立“Evening Complex—MYC2—SAG29—叶片衰老”模型等。本项目将精细解析生物钟调控茉莉酸诱导植物叶片衰老的机理，为分子设计育种提供借鉴。

生物钟是生物体为了适应环境昼夜周期变化而进化出的协调细胞内基因表达、代谢网络调控的分子系统，调控植物的新陈代谢、生长发育等多个过程。生物钟使植物的内源节律与外部昼夜变化的光和温度等环境条件相协调，为植物的生长发育提供竞争性优势。叶片衰老过程能够将营养和能量从衰老的叶片向正在发育的组织和器官转移，以便更好地适应环境胁迫，但生物钟是否参与调控叶片衰老过程目前尚不清楚。本项目从生物信息学、生理学、分子生物学以及遗传学等角度阐释了生物钟核心组分Evening Complex在调控植物叶片衰老过程中发挥的功能及分子机理。主要研究发现Evening Complex各亚基突变体叶片衰老提前而过表达材料则延缓衰老，Evening Complex相关突变体的转录组分析表明Evening Complex可能通过茉莉酸信号调控叶片衰老，进一步结合生物信息学预测以及生化分子实验鉴定到Evening Complex调控叶片衰老的直接靶基因为MYC2，最后遗传学实验也验证了Evening Complex对MYC2的分子遗传调控关系。因此本项目精细解析了Evening Complex调控茉莉酸诱导叶片衰老的作用机制。“Evening Complex-MYC2”这一生物钟与茉莉酸信号互作的新模块，为作物分子设计育种提供理论借鉴。通过本项目，我们在Molecular Plant、International Journal of Molecular Sciences、Frontiers in Plant Science和Plant Physiology发表论文4篇。