大豆GmLBD36蛋白调控基因沉默和防卫反应的机理研究

卵菌是一类极具毁灭性的真核微生物。最近研究表明，RNA沉默抑制也是卵菌抵抗宿主免疫反应的重要防御手段，但其具体的分子机理还不清楚。我们近来鉴定了一个新的大豆疫霉效应子PsAvh111能够抑制L1植株中GUS基因沉默。初步结果表明，PsAvh111是疫霉侵染大豆所必须的毒性因子；可以促进疫霉和病毒的侵染；并且通过与宿主GmLBD36蛋白的互作诱导靶基因的显著上调表达。此外，GmLBD36具有內源RNA沉默抑制活性。在此基础上，本项目拟以GmLBD36基因为研究对象，通过效应子与GmLBD36互作研究，明确GmLBD36在大豆疫侵染过程中的作用模式；阐明GmLBD36对mRNA去帽酶的表达和活性影响；解析效应子通过激活GmLBD36的表达，使RNA沉默途径与mRNA 降解途径竞争相似的RNA底物来抑制大豆防卫反应的作用机制，其结果将为大豆疫霉根腐病的防治提供重要的理论。

Oomycete belongs to one of the most prominent eukaryotic plant pathogenic organisms. our previous results indicated that RNA silencing is also an important defence strategy against oomycete pathogens in plants. However, the specific mechanism of how oomycete effectors suppress host RNA silencing remains elusive. Recently, we identified a novel suppressor of RNA silencing, PsAvh111, in Phytophthora sojae (P. sojae) RxLR effectors using a stable transgenic system that effector genes was overexpressed in L1 plants, then investigated the suppression of GUS gene silencing in transgenic L1 plants. Our preliminary data showed that the PsAvh111 is required for full virulence in P. sojae, and enhance the plant susceptibility to both PVX virus and Phytophthora parasitica in Nicotiana benthamiana leaves and to P.sojae in soybean hair root. Through co-IP combined with MS screening, we identified GmLBD36a/b as a novel interacting protein of PsAvh111 and greatly induce GmLBD36a/b gene expression in soybean. And GmLBD36a/b encode endogenous suppressor of RNA silencing. In this proposal, our research is focused on the molecular mechanism of GmLBD36a/b in manipulating host immunity and promoting mRNA degradation by decapping pathway in soybean. Our final objective is to fully understand the pathogenic mechanism by competing for similar RNA substrates between RNA silencing pathway and mRNA decay pathway. Success of this project will pave the way for elucidating pathogenic mechanism of Phytophthora effectors and developing new strategy for Phytophthora root and stem rot disease control.