拟南芥转录因子JIP5参与茉莉酸调控芥子油苷水解过程的分子机制研究

Glucosinolate hydrolysis process mediated by myrosinase plays an important role in plant immunity, and this process is regulated by plant hormones jasmonic acid. However how jasmonic acid regulation glucosinolates hydrolysis process is still not clear. Our team got a transcription factor named JIP5 protein (JAZ-interaction protein 5) which has direct interaction with JAZ proteins through a preliminary screening by yeast two hybrid method. The preliminary experiment showed that jip5 mutant plant had lower expression of myrosinase genes, TGG1 and TGG2 induced by JA, where jip5 mutant plant had no other significant phenotypes mediated by JA. This suggests that JIP5 may specific participate in jasmonic acid mediated glucosinolates hydrolysis process. This project intends to further study the role of JIP5 in the glucosinolates hydrolysis process and explore the genetic relationship between JIP5 and the key components of jasmonic acid signal pathway in the glucosinolates hydrolysis process by using the means of genetics. At last we will find JIP5 direct target gene in the glucosinolates hydrolysis process through complete genomics method. The final aim of our project is to clarify the JA-JAZ-JIP5-myrosinase pathway which will have a good enricment to the mechanism research of plant resistance to chew type insect.

黑芥子酶介导芥子油苷水解过程在植物抗病虫害过程中起着重要的作用，这个过程受到植物激素茉莉酸的调控。然而，茉莉酸如何调控芥子油苷水解过程仍不清楚。前期我们利用酵母双杂交技术筛选得到一个与JAZ蛋白互作的转录因子JIP5（JAZ-interaction protein 5）。初步发现，jip5突变体中茉莉酸诱导的黑芥子酶编码基因TGG1和TGG2表达呈显著下调，而jip5突变体对茉莉酸介导的其他反应没有显著表型，表明JIP5可能特异的参与茉莉酸调控芥子油苷水解过程。本项目拟通过遗传学等手段深入研究JIP5在芥子油苷水解过程中的作用，并探究JIP5与茉莉酸信号传导途径关键元件在芥子油苷水解过程中的遗传学关系。最后通过全基因组学的方法寻找JIP5在芥子油苷水解过程中的直接靶基因。从而阐明茉莉酸→JAZ→JIP5→黑芥子酶这一信号传导途径，对充实植物抵抗咀嚼式昆虫的机制研究有很好的促进作用。

目前研究都集中在茉莉酸调控芥子油甘的合成过程，但是对于茉莉酸调控芥子油甘的水解过程还不清楚。本项目以前期发现茉莉酸信号通路中关键转录抑制子JAZ蛋白能够与芥子油甘水解过程中关键转录因子FAMA有互作关系，并以此为切入点，深入分析茉莉酸通过FAMA来调控芥子油甘水解过程，取得主要成果如下：确认了JAZ蛋白与FAMA的互作关系。通过酵母双杂、烟草split-luc系统以及co-ip等技术，多方面验证了JAZ蛋白的确与FAMA有互作关系，并发现JAZ蛋白的Jas功能域对于互作是必需的。明确了FAMA在芥子油甘水解过程中的作用，fama突变体能够降低黑芥子酶的活性，增加芥子油甘的含量；而FAMA过表达则能提高黑芥子酶的活性，降低芥子油甘的含量。解析了茉莉酸信号分子在芥子油甘水解过程中的作用。茉莉酸受体突变体coi1-2和JAZ蛋白的缺失Jas功能域的植株中黑芥子酶的活性降低，而且coi1-2突变体中TGG1和TGG2基因表达下降。阐明了FAMA调控芥子油甘水解的机理。FAMA能够结合到TGG1和TGG2的启动子上，调控TGG1和TGG2的表达，而这种调控受到JAZ蛋白的调节。最后解析了COI1调控的芥子油甘水解过程，即COI1信号通过调控FAMA的表达，从而激活下游TGG1和TGG2的表达，来激活芥子油甘的水解过程。本项目不仅阐述了茉莉酸调控芥子油甘水解的机理，还为利用茉莉酸在植物抗虫害过程中提供重要理论依据。