番茄黄脉花叶病毒（TYVMV）是一个新鉴定的单组份双生病毒新种，前期研究发现，其V2既是一个强致病因子、又具有PTGS强抑制子功能还能诱导寄主过敏性反应。但至今对这类V2蛋白的致病机理未见系统研究。本项目拟以TYVMV编码的V2为诱饵，利用Y2H从本氏烟cDNA文库中筛选与V2互作的大量寄主因子，BiFC和Co-IP等方法验证其互作；截段突变或点突变筛选V2互作的关键位点，明确关键位点突变对其抑制子功能、致病及诱导HR能力的影响；构建各V2突变体病毒的侵染性克隆，分析其致病性差异；在V2转基因植株、各V2突变体病毒/野生型病毒接种植株中比较各寄主因子表达量的变化，明确V2与各寄主因子的互作功能及对其信号途径的影响；将寄主因子过表达或沉默后，接种病毒及各V2突变体病毒，检测其对病毒致病及V2功能的影响。由此揭示V2多途径调控寄主因子逃逸植物的防御体系实现病毒成功侵染的分子机制。

Tomato yellow vein mosaic virus (TYVMV) is a distinct monopartite begomovirus in China. Previous data showed V2 encoded by TYVMV was a multifunctional protein as a powerful pathogenic factor, viral suppressor of post transcriptional gene silencing and a determinant of hypersensitive response. While the pathogenic mechanism caused by this kind of V2 was unknown. In this project, the host factors interacted with V2 will be screened using Yeast two hybrid system (Y2H), and will be confirmed by Bimolecular Fluorescence Complementation (BiFC) and Co-Immunoprecipotation (Co-IP). The V2 mutants will be constructed and the V2 key sites critical for V2/host factors's interaction will be identified by Y2H、BiFC or Co-IP, and their influence in inducing PTGS、symptom determinant and hypersensitive response will be assessed. The infectious clones of V2 mutants (TYVMVmV2) will be constructed and the viral pathogenicity will be analyzed. To understand the interaction function of V2 and these host factors, the transcripts level and protein level of host factors will be tested in V2 transgenic plants, the TYVMVmV2-infected and the wild TYVMV-infected plants. The host factors overexpressed or knocked down plants were produced, and challenged by the TYVMVmV2 or the wild TYVMV, and the infection efficiency、the viral accumulation and V2 activity in these plants will be analyzed to learn the effect of viral pathogenicity caused by the host factors. With these research work above, it will expand our knowledge of the biological mechanism of V2 encoded by TYVMV regulate the host factors to counter host defense for viral infection.