假马鞭曲叶病毒和中国胜红蓟黄脉病毒C4蛋白是RNA沉默的抑制子

为了研究中国胜红蓟黄脉病毒(Ageratum yellow vein Chin virus,AYVCNV)和假马鞭曲叶病毒(Stachytarpheta leafcurl virus,StaLCV)C4蛋白的功能,利用烟草脆裂病毒(Tobacco rattle virus,TRV)载体在本氏烟(Nicotianabenthamiana)中分别表达了这两种病毒的C4蛋白,结果发现它们均能在本氏烟中引起类似于病毒侵染的症状,推测AYVCNV和StaLCV的C4蛋白是病毒的致病因子;在RNA沉默的抑制试验中,AYVCNV和StaLCV的C4蛋白均能够在表达gfp基因的转基因本氏烟(16c)上抑制由gfp基因正义链引起的基因沉默的建立,证明它们都是RNA沉默的抑制子。

The C4 proteins of Ageratum yellow vein China virus and Stachytarpheta leaf curl virus are suppressors of RNA silencing

RNA silencing is a highly conserved mechanism in many eukaryotic organisms that involves sequence-specific RNA degradation. One of the important roles of RNA silencing is antiviral infection. To counter this defense mechanism, many plant viruses have evolved or acquired functional proteins (suppressors) for suppression of RNA silencing. Geminiviruses are a family of small circular single-stranded DNA (ssDNA) viruses that cause severe diseases in major crop plants worldwide. AC2 (C2) and AC4 (C4) proteins of many geminiviruses were reported to be suppressors of RNA silencing. Ageratum yellow vein China virus (AYVCNV) and Stachytarpheta leaf curl virus are two distinct geminiviruses identified in China. In this study, the functions of C4 of AYVCNV and StaLCV were studied, analysis of infectivity of AYVCNV and StaLCV C4 genes using Tobacco rattle virus (TRV) vector were carried out in Nicotiana benthamiana plants, N. benthamiana plants expressing C4 can induce the virus-like symptoms, indicating that the C4 gene of AYVCNV or StaLCV is symptom determinant. In experiment of suppression of RNA silencing, C4 protein of AYVCNV or StaLCV can suppresses the local silencing of gfp in transgenic N. benthamiana plants (16c), suggests that both of them are suppressors of RNA silencing. The above results indicate that C4 of AYVCNV or StaLCV is a symptom determinant and suppressor of RNA silencing.