叶绿体信号识别颗粒54kD亚基（cpSRP54）在水稻条纹病毒侵染过程中的功能研究

Chloroplasts are the sites of photosynthesis in plant cells and participate in signal communication between organelles and plant defense responses. Chloroplasts are considered to be the common target attacked by many plant viruses. In-depth study of chloroplast protein function is of great significance for understanding the pathogenesis of viruses and host antiviral mechanisms. CpSRP54 is a chloroplast protein identified in Nicotiana benthamiana by quantitative proteomics in our laboratory. Its normal function is mainly responsible for transporting light-harvesting chlorophyll-binding proteins (LHCPs) from chloroplast stromal to thylakoid membrane. RSV infection can reduce the transcript amount and protein accumulation of cpSRP54 and the cpSRP54 gene silencing tobacco plants constructed by TRV-mediated gene silencing technology showed susceptibility compared to control plants after inoculation with RSV which led to the discovery that RSV infection could destroy the normal function of cpSRP54 and that cpSRP54 mediated downstream genes may be involved in host antiviral responses. In addition, jasmonic acid content in cpSRP54-silenced tobacco was significantly reduced, indicating that cpSRP54 silencing interferes with normal JA synthesis in plants. This study intends to use a variety of techniques to elucidate the molecular mechanism of RSV affecting the function of cpSRP54 and to explore the downstream genes of cpSRP54.

叶绿体是植物细胞中光合作用的场所，并参与细胞器之间的信号交流及植物抗病防卫反应。叶绿体被认为是众多植物病毒侵染时共同的攻击靶标，深入研究叶绿体蛋白功能对理解病毒致病及寄主抗病毒机制具有重要意义。cpSRP54是我们实验室前期通过定量蛋白质组学技术在本氏烟中鉴定到的一个叶绿体蛋白，它的正常功能主要是负责将光捕获叶绿素结合蛋白从叶绿体基质转运至类囊体膜。RSV侵染能降低cpSRP54的转录本及蛋白质积累量，同时cpSRP54基因沉默烟草植株接种RSV后表现出比对照植物感病，由此可以推出RSV侵染能破坏cpSRP54的正常功能，cpSRP54介导的下游基因可能参与寄主抗病毒反应。此外，cpSRP54沉默的烟草中茉莉酸含量显著降低，表明cpSRP54沉默干扰了植物体内JA的正常合成。本研究拟综合采用多种技术阐明RSV影响cpSRP54功能的分子机制及探索cpSRP54调节的下游基因。

叶绿体是植物细胞中光合作用的场所，并参与细胞器之间的信号交流及植物抗病防卫反应。叶绿体被认为是众多植物病毒侵染时共同的攻击靶标，深入研究叶绿体蛋白功能对理解病毒致病及寄主抗病毒机制具有重要意义。茉莉酸（JA）是植物抗病毒免疫过程中的一种重要激素，越来越多的证据表明植物病毒能通过干扰JA的合成和信号反应来对抗寄主的防卫反应。本项目对叶绿体类囊体膜蛋白转运蛋白NbcpSRP54在水稻条纹病毒（RSV）和芜菁花叶病毒（TuMV）侵染过程中的功能开展了系列研究。发现NbcpSRP54介导本氏烟抗病毒免疫活性正常发挥，RSV和TuMV侵染均能减少NbcpSRP54的蛋白积累量及JA正常含量。NbcpSRP54能与JA合成途径重要基因NbAOC.1互作，并介导了NbAOC.1正确定位到叶绿体类囊体膜。RSV和TuMV侵染也都能干扰NbAOC.1在胞内的正确定位。不同病毒的沉默抑制子蛋白（TuMV的P1蛋白、马铃薯X病毒（PVX）的p25、辣椒轻斑驳病毒（PMMoV）的p126）都能以泛素蛋白酶体和自噬途径依赖的方式介导NbcpSRP54的降解，表明NbcpSRP54是不同病毒共同选择的一个攻击靶标。