内质网叶绿体互作及其在植物抗病毒过程中作用

Both endoplasmic reticulum (ER) and chloroplast are important organelles that in charge of the biosynthesis of proteins, nucleotides, lipids, ATP, and other molecules. Therefore, the ER- chloroplast membrane contact sites (MCSs) may be more active in the biosynthesis of different molecules. The replications of viruses need synthesizing a large amount of proteins, nucleotides, and other molecules. At the same time, the replications of viruses consume a large amount of ATP. Therefore, ER-chloroplast MCSs provide ideal loci for viruses to perform replication processes. RNA silencing is the major anti-viral mechanism in plants. The replications of viruses lead the accumulation of double-stranded RNA (dsRNA), the inducer of RNA silencing. The quickly replication of viruses thus recruit the key components of RNA silencing to the viral replication loci to suppress viral replications. However, we know little about the connection of ER with chloroplast, as well as the replications of viruses and RNA silencing at the ER-chloroplast MCSs. Our preliminary data shows that: ER and chloroplast are tightly connected; viruses replicate at the ER-chloroplast MCSs; AtAGO2, the key component of RNA silencing, interacts with RBP1, a chloroplast localized protein, at ER-chloroplast MCSs; RH3 facilitates the plant resistance to viruses. Next, we will focus on the ER-chloroplast MCSs, and determine the interaction of AtAGO2 with RBP1. The replications of different viruses and enrichment of other RNA silencing components at the ER-chloroplast MCSs will be studied, respectively. Successful implementation of this proposal will improve our understanding on the connection network of organelles. With these cell biological studies, it will also provide a novel insight into the plant immunity and RNA silencing mechanisms.

内质网与叶绿体均是细胞内非常活跃的生物合成中心，其交联部位的生物合成与互作更为活跃。病毒的快速复制不仅需要大量合成蛋白质和核酸等生物大分子，并且要消耗大量的能量，内质网与叶绿体交联部位将为病毒的复制提供理想场所。RNA沉默是植物抗病毒的主要机制，病毒复制必然招募RNA沉默抗病毒组份在复制位置富集抑制其扩增。申请人前期发现内质网与叶绿体紧密相连；植物病毒在交联部位复制；RNA沉默核心蛋白AtAGO2与叶绿体定位的RBP1为两个细胞器互作的关键因子，并参与植物抗病毒反应。项目将聚焦内质网与叶绿体的交联互作，以AtAGO2与RBP1的互作为切入点，环环相扣深度解析内质网与叶绿体互作对病毒复制的调控机制；阐释抗病毒RNA沉默组份在交接位置的富集及抗病毒功能。研究的开展将完善对细胞器互作的认识，揭示内质网与叶绿体的关键蛋白在交联互作中的作用，并从细胞生物学角度加深对RNA沉默和植物与病毒互作的理解。

叶绿体普遍被认为是由原核蓝藻在植物细胞中内共生进化而来，然而其与真核细胞特异的RNA沉默功能仍然未知。鉴于RNA沉默在植物抗病毒免疫中的重要作用，我们探索了RNA沉默与植物抗病毒免疫之间的细胞生物学联系。我们发现，拟南芥Argonaute2（AGO2）在内质网-叶绿体膜接触位点装载sRNAs。RH3是一种叶绿体定位的RNA解旋酶，它与AGO2相互作用，并在内质网-叶绿体的膜接触位点促进内源性sRNA和外源性病毒sRNA装载到AGO2中。此外，内质网-叶绿体膜接触位点被证明是病毒的复制的重要位点之一。我们的研究表明，内质网-叶绿体膜接触位点为RNA沉默和病毒复制提供了空间，揭示了叶绿体在RNA沉默中的新功能，并揭示了RNA沉默与宿主抗病毒免疫之间的细胞生物学相关性。