黄瓜花叶病毒（CMV）基因组RNA2通过其亚基因组RNA4A产生RNA沉默抑制子2b蛋白。前期研究发现：番茄不孕病毒(TAV) RNA1与CMV RNA2的异源组合不能有效合成CMV亚基因组RNA4A，但支持其它病毒RNA的有效合成。由此，我们推断RNA1编码的复制酶组分1a蛋白在亚基因组RNA4A的合成中扮演重要的角色。那么，CMV 1a蛋白如何调控病毒亚基因组RNA4A的合成？为回答这个问题，本项目首先通过比较同源（CMV 1a/CMV 2a）和异源（TAV 1a/CMV 2a）复制酶对CMV亚基因组RNA4A合成的影响，明确CMV 1a蛋白在病毒亚基因组RNA4A合成中的重要性。然后，通过分析CMV 1a和TAV 1a蛋白的片段交换重组体以及点突变体对CMV亚基因组RNA4A合成的情况，明确调控CMV 亚基因组RNA4A合成的1a蛋白功能域或功能位点，初步阐明CMV 1a蛋白调控病毒亚基因组RNA4A合成的分子机制。

Cucumber mosaic virus (CMV) genome RNA2 produces RNA silencing suppressor 2b protein via its subgenome RNA4A. Previous finding shows that hetero-combination of Tomato aspermy virus (TAV) RNA1 and CMV RNA2 did not efficiently produce CMV subgenome RNA4A, but supported synthesis of other viral RNAs. On basis of this finding, we speculated that viral replicase component 1a protein encoded by RNA1 plays an important role in production of subgenome RNA4A.Then, we questioned how CMV 1a protein regulates synthesis of subgenome RNA4A? To do this, firstly this grant will confirm importance of CMV replicase component 1a protein in synthesis of subgenome RNA4A by comparing effect of heterogenous helicase (CMV 1a/CMV 2a) and homogenous helicase (TAV 1a/CMV 2a) on synthesis of CMV subgenome RNA4A. Afterwards, an effort will be made to uncover the molecular basis of CMV 1a protein regulating synthesis of viral subgenome RNA4A by determining 1a function domain responsible for RNA4A synthesis, RNA4A promoter sequence recognized by 1a, and interactions of 1a and 2a proteins with RNA4A promoter.