液泡分选受体介导芜菁花叶病毒6K2转运促进病毒侵染的作用机制研究

芜菁花叶病毒（TuMV）是我国农业生产上普遍发生的重要马铃薯Y病毒属成员。病毒6K2蛋白是病毒复制复合体（VRC）囊泡形成的关键因子，其如何靶向多囊泡体（MVB）进行复制和进入质外体完成胞间运动的机制不明。鉴定该过程的重要寄主因子可为开发防病毒策略提供新的切入点。本研究聚焦本氏烟液泡分选受体（VSR）介导的蛋白转运途径，发现VSR4促进TuMV侵染，且和6K2特异性互作，VSR4标记的MVB颗粒和6K2诱导的VRC囊泡共定位。这些结果暗示VSR4可能介导6K2靶向MVB进行复制。我们拟进一步分析VSR4和6K2互作对TuMV复制和胞间运动的影响，VSR转运功能的缺失对6K2转运和TuMV侵染的影响以及VSR4是否介导6K2向质外体运输及其作用机制。研究结果将促进我们对病毒VRC囊泡运输的认识和VSR在其中的作用机制，为今后通过遗传修饰进行作物抗病毒育种提供靶标。

Turnip mosaic virus is a widely distributed potyvirus member and infects many agriculturally important crops in China. The second 6-kDa viral protein 6K2 is essential for vesicular viral replication complex (VRC) formation. TuMV VRC can target multivesicular body (MVB) for replication and enters apoplast for intercellular movement, however, the detailed mechanisms are still largely unknown. Identification of critical host factors involving in this process will provide a new potential target of anti-viral strategies. Here, we focus on the vacuolar sorting receptor (VSR)-mediated protein trafficking pathway in Nicotiana benthamiana cells. We found that the VSR4 is a proviral host factor of TuMV, and can interact with TuMV 6K2 specifically. Moreover, the VSR4-labelled MVB punctate bodies co-localized with 6K2-induced TuMV VRC. These results suggest that VSR4 may mediate trafficking of 6K2 to MVB for replication. Here, we will further determine the role of 6K2-VSR4 interaction in TuMV replication and intercellular movement, investigate the effect of dominant negative mutant of VSR4 on 6K2 trafficking and TuMV infection, and identify possible role of VSR4 in the release of 6K2-induced vesicles to extracellular space. These results will promote our understanding of TuMV vesicular VRC trafficking and elucidate the molecular mechanisms of VSR in this progress, and provide important information for anti-viral breeding by genetic modification of candidate host genes in crops.