甘薯病毒G CH株系和CH2株系中国分离物基因组全序列克隆及结构特征分析

为明确甘薯病毒G(sweet potato virus G,SPVG)CH株系中国分离物SPVG-CH-Ch1和CH2株系中国分离物SPVG-CH2-Ch1的基因组结构特征及遗传变异情况,利用RT-PCR和RACE方法克隆获得分离物SPVG-CH-Ch1和SPVG-CH2-Ch1的基因组全序列,应用DNAMAN软件对基因组全序列及不同编码区序列进行分子变异分析,并基于多聚蛋白基因序列利用MEGA 7软件进行系统进化分析。结果表明,分离物SPVG-CH-Ch1和SPVG-CH2-Ch1的基因组分别包含10 813个和10 834个核苷酸,均包含1个开放阅读框,由10 467个核苷酸组成,编码含有3 488个氨基酸残基的多聚蛋白。分离物SPVG-CH-Ch1与SPVG-CH2-Ch1之间的基因组全序列核苷酸一致性为78.6%,二者与GenBank中登录的其它SPVG分离物基因组全序列核苷酸一致性分别为78.6%～99.1%和77.9%～98.6%,其中SPVG-CH-Ch1与IS103分离物(KM014815)的核苷酸一致性最高,为99.1%,与WT325分离物(KF790759)的核苷酸一致性最低,为78.6%;SPVG-CH2-Ch1与WT325分离物的核苷酸一致性最高,为98.6%,与66Al分离(KX279878)的核苷酸一致性最低,为77.9%。系统进化树显示,SPVG-CH-Ch1与CH株系的7个分离物形成1个分支,SPVG-CH2-Ch1与CH2株系的WT325分离物形成1个分支。表明SPVG的CH株系和CH2株系之间的变异较大,株系内较保守。

Complete nucleotide sequence and characterization analysis of the sweet potato virus G CH and CH2 strains isolated from China

In order to elucidate the complete genomic organization and molecular variability of the sweet potato virus G (SPVG) CH and CH2 strains isolated from China, which named SPVG-CH-Ch1 and SPVG-CH2-Ch1, the complete genomic sequences of them were amplified by RT-PCR and RACE, genetic variation analysis of complete genomic sequences and individual protein sequences were per-formed using DNAMAN, and neighbor-joining phylogenetic tree of them with other isolates was gener-ated using MEGA 7.0 software. The results showed that the complete genomic sequence of the two iso-lates were 10 813 nucleotides (nt) and 10 834 nt in length, respectively. The genomic organizations of the two isolates contained one open reading frame of 10 467 nt encoding a polyprotein of 3 488 amino acids. The SPVG-CH-Ch1 isolate exhibited nt sequence identity of 78.6% with SPVG-CH2-Ch1 isolate. Pairwise comparisons showed that SPVG-CH-Ch1 and other SPVG isolates deposited in GenBank data-base shared 78.6%-99.1% nt sequence identity at the complete genomic sequence level. It was most closely related to the isolate IS103 (KM014815) with 99.1% nt identity and showed the lowest nt identi-ty with isolate WT325 (KF790759) by 78.6%. SPVG-CH2-Ch1 and the other SPVG isolates shared 77.9%-98.6% nt sequence identity at the complete genomic sequence level. It had the highest nt identi-ty with isolate WT325 (KF790759) by 98.6%, and the lowest nt identity with isolate 66Al (KX279878) by 77.9%. Phylogenetic tree analysis based on the polyprotein gene placed SPVG-CH-Ch1 isolate in CH strain and SPVG-CH2-Ch1 in CH2 strain containing WT325. The results indicated that SPVG had great genetic variability between CH and CH2 strains, but high degree of conservation in strains.