中国甘薯双生病毒外壳蛋白基因分子变异及遗传多样性分析

Molecular variation and genetic diversity analysis of coat protein gene in Sweetpoviruses in China

甘薯双生病毒是中国甘薯上一类重要病毒,其外壳蛋白(coat protein,CP)基因具有介体传毒、基因包被等多功能。揭示其分子变异,可以为病毒防治及育种工作提供理论依据。利用PCR方法扩增获得了24个甘薯双生病毒分离物的cp基因,采用SDT、Dna SP、RDP3、MEGA等软件对其进行分子变异分析。结果表明:24个分离物核苷酸序列均为765个碱基,一致率为88.3%~100%,编码254个氨基酸,一致率为94.5%~100%。中国甘薯双生病毒分离物系统进化树分为2个组,组I包括大部分分离物及本研究获得的22个分离物,又分为了2个亚组;组Ⅱ含有29个分离物,包括本研究中的XU8_2和XU8_3,这2个分离物与其他分离物可能为不同的种。非同义突变与同义突变比值大于1,说明cp基因处于正向选择即多样化选择。错配分布图除亚组1相对比较平滑外,其余组或亚组分离物均为多峰锯齿状,表明除亚组1种群呈突然暴发的状态外,其他组或亚种群已经存在很长时间,处于动态平衡状态。

The objectives of this study were to study the gene and gene variation of Sweetpoviruses infecting Ipomoea batatas in China. Sweetpovirus coat protein gene fragments of 24 isolates from sweet potato were ampl ified by PCR u-sing the infected leaf samples randomly collected from sweet potato research center and SDT, DnaSP, RDP3 , MEGA and other software were used to analysis testifies. The result showed that, the nucleotide sequences and amino acid sequences showed similarieties of 88. 3% - 100% and 94. 5% - 100% , respectively fo r the 24 isolates containing 765 base pairs and 254 amino acids. Phylogenetic trees constructed with all Chinese isolates revealed that the isolates were divided into 2 groups. Group I included most o f the isolates collected from China, and 22 isolates obtained in this study, and divided into 2 subgroups. Group II included only 27 isolates from Genbank and 2 isolates, XU 8_2 and XU8_3 obtained in this study, so these 2 isolates might be new species. The ratio between mutations in the non-synonymous and synonymous sites （dN/ds ratio ） of cp was 〉 1 , implying the coat protein gene was under positive selection. The shapes of mismatch distribution of Sweetpoviruses for all groups and subgroups except subgroup I were multimodal and ragged, indicating that all these population/subpopulations were long-existing ones.