可可毛色二孢菌效应子LtCre1与其寄主靶标基因的识别及应答机制

Botryosphaeria dieback caused by the botryosphariaceous pathogen Lasiodiplodia theobromae is one of the most important trunk diseases in the world. This disease has seriously affected the grape yield and quality in primary grape production areas. Host target identification for L. theobromae effectors in grapevine helps to understand the infection mechanism of the pathogen. However, it is still in its infancy. Our previous study showed that the expression of the effector LtCRE1from L. theobromae was induced during infection. This gene is most likely to encode a secreted protein with histone acetyltransferases domain. In addition, using transient expression assays in Nicotiana benthamiana, we found that LtCRE1could resulted in Burkholderia glumae- and BAX-induced cell death. Also, overexpression of LtCRE1 in L. theobromae enhanced disease severity. Therefore, yeast two-hybrid assays or MS methods will be conducted in this study to screen and identify target genes in grapevine which interact with LtCre1. We will also investigate how the target genes regulate plant immunity. In conclusion, these results will ascertain the role of LtCre1 in regulating plant immunity in grapevine. This will eventually lead us to find new target genes for L. theobromae control, which will facilitate the development of new control strategies for Botryosphaeria dieback.

可可毛色二孢菌是广泛引起木本植物枝干病害的植物机会病原真菌，其在我国引起的葡萄溃疡病发生危害严重。解析可可毛色二孢菌中效应蛋白与寄主体内靶标互作有助于我们深入理解可可毛色二孢菌引起病害的发生过程，但到目前为止尚未见到该菌中效应蛋白与寄主靶标互作的相关报道。我们的前期实验发现：效应子LtCRE1基因在可可毛色二孢菌侵染葡萄的过程中诱导表达，推定编码产物具有组蛋白乙酰转移酶活性，该基因的编码产物具有细胞死亡抑制活性，在可可毛色二孢菌中的超表达可增强病原菌的致病力。本研究拟通过酵母双杂交、质谱、蛋白互作、转基因等技术解析LtCre1在寄主中的作用位点、作用靶标及其互作调控机理，明确其与LtCre1互作的生物学意义。该研究有助于揭示木本植物机会病原菌的侵染机制以及该类病菌与寄主防卫反应的互作机制，为该类病菌高效防治策略的构建提供理论指导。

可可毛色二孢菌（Lasiodiplodia theobromae）是枝干病害葡萄溃疡病的主要致病菌之一，严重危害葡萄产业健康发展。病原真菌向寄主体内分泌多种效应因子来抑制寄主免疫反应以促进侵染定殖。然而，可可毛色二孢菌效应子调控寄主免疫的机制尚不明晰。前期实验，从可可毛色二孢菌中克隆获得效应子LtCre1，该效应子在烟草上可抑制BAX诱导的细胞坏死。遗传转化证实，效应子LtCre1的超表达转化子显著提高可可毛色二孢菌的毒力，而其RNAi干涉转化子的毒力显著降低。另外，效应子LtCre1在烟草上的异源表达降低了植株的抗病力，说明效应子LtCre1是可可毛色二孢菌一个重要的毒力因子。蛋白互作分析证实，效应子LtCre1与寄主葡萄RGS1-HXK1-interacting protein 1 （VvRHIP1）发生相互作用。VvRHIP1在烟草上的异源表达增强了植株对可可毛色二孢菌的抗病力，说明VvRHIP1是植物免疫一个正调控因子。进一步研究发现，LtCre1能够破坏VvRHIP1与糖受体蛋白VvRGS1的复合体的形成。并且，效应子LtCre1参与调节寄主植物糖信号传导途径。该研究结果表明，效应子LtCre1能够竞争性与VvRHIP1结合，通过破坏VvRHIP1与糖受体蛋白VvRGS1的互作，干扰寄主植物糖信号途径的正常传导，并抑制寄主的免疫反应，从而促进可可毛色二孢菌对寄主植物的侵染。