中国甘薯双生病毒C4基因分子变异及遗传多态性分析

Molecular variation and genetic polymorphism of C4 gene in sweepoviruses of China

甘薯双生病毒是中国甘薯上一种重要的病毒,其C4基因编码的蛋白是一个多功能蛋白,参与了寄主症状的形成及病毒在植物体内移动等。本研究利用PCR方法扩增了24个分离物的C4基因,通过SDT、Dna SP等软件分析,结果表明,24个分离物核苷酸序列均为258个碱基,一致率为73.3%~100.0%,编码85个氨基酸,一致率为47.1%~100.0%。中国甘薯双生病毒分离物C4基因构建系统进化树分为2个组,组Ⅰ包括本研究的15个双生病毒分离物及中国大部分双生病毒分离物,又分为2个亚组,亚组2仅有15个双生病毒分离物,其中本研究的6个分离物位于此亚组;组Ⅱ含有30个双生病毒分离物,包括本研究的9个分离物。非同义突变与同义突变比值大于1,说明C4基因处于正向选择。亚组1错配分布图为单峰,说明该组种群呈突然暴发的状态,其余组或亚组为多峰锯齿状,表明种群或者亚种群已经存在很长时间,长期处于动态平衡。

The multi-functional protein encoded by C4 gene of sweepovirus is involved in the host symptoms forma-tion and the virus movement. To characterize the C4 gene infecting Ipomoea batatas in China, the gene fragments of 24 iso-lates from sweet potato were amplified by PCR and analyzed by SDT, DnaSP and so on. The nucleotide sequences and ami-no acid sequences of the 24 isolates shared similarities of 73.3%-100. 0% and 47.1%-100. 0%, respectively, containing 258 base pairs and 85 amino acids. Phylogenetic trees constructed based on C4 gene revealed that the isolates were divided into two groups. GroupⅠincluded most of the isolates collected from China and 15 isolates in this study, and was divided into two subgroups. GroupⅡincluded 21 isolates from Genbank and 9 isolates in this study. The ratio of nonsynonymous mu-tation to synonymous mutation （ dN/dS ratio） of C4 gene was 1.53, indicating that C4 gene was under positive selection. The mismatch distribution of sweepoviruses for all groups and subgroups except subgroup 1 shaped multimodal and jagged, sug-gesting that the population/subpopulations were long-exist-ing.