瓜类褪绿黄化病毒新疆分离物基因组分析

The genome of Cucurbit chlorotic yellows virus from Xinjiang autonomous region of China

2016年秋季,新疆维吾尔自治区吐鲁番市哈密瓜大面积发生叶片黄化和褪绿的病害,症状呈瓜类褪绿黄化病毒(Cucurbit chlorotic yellows virus,CCYV)引起的典型特征。通过CCYV的特异性引物对该疑似样本进行了RT-PCR检测,获得了预期大小的扩增片段。随后,对新疆的CCYV分离物(CCYV-Xinjiang)全长基因组进行克隆并测序,获得了CCYV-Xinjiang分离物的RNA1和RNA2全长序列信息。对CCYV-Xinjiang和来自Gen Bank数据库的其他CCYV分离物的基因组序列分析,不同分离物RNA1和RNA2两条链的一致性分别是99.65%~99.93%和99.68%~99.89%。单独对基因组的各个非翻译区(UTRs)和编码区的核苷酸变异分析,数据表明不同区域其变异程度不同,其中RNA2的3'UTR区域变异最大,而RNA1的2个UTRs区域变异最小。对已登录Gen Bank的所有CCYV分离物基因组系统进化树分析结果表明,所有分离物聚在同一个组。另外,对来自Gen Bank的18个分离物的外壳蛋白(CP)氨基酸序列进行系统进化树分析,表明来自伊朗的3个分离物分在组2(GroupⅡ),而来自亚洲其他地区的分离物均被分到组1(GroupⅠ)。基于CCYV基因组的信息,发现来自亚洲地区的CCYV的群体遗传变异很小。

In the autumn of 2016, an outbreak of a disease causing yellowing and chlorosis on leaves was observed on Hami melon plants in Turpan City of Xinjiang Uygur Autonomous Region. Samples that are similar to typical symptom caused by Cucurbit chlorotic yellows viurs （CCYV） were collected. RT PCR using CCYV specific primer pairs resulted in amplified DNA fragments of predicted size. Complete RNA1 and RNA2 of CCYV isolated from Xijiang （CCYV Xinjiang） were cloned and sequenced. Identity analysis showed that the nucleotide identities of the complete RAN1 and RNA2 sequences of CCYV Xinjiang as well as other CCYV isolates from GneBank database ranged between 99.65% 99.93% and between 99.68% 99.89%, respectively. Nucleotide diversity of each ORFs and untranslated regions （UTRs） was also determined independently ; and the data showed that variability is not distributed evenly among the different regions of viral genomes, with the 3’ UTR of RNA2 and both of the UTRs of RNA1 showing the most and least diversity, respectively. Phylogenetic analysis based on the genomes of all of the CCYV isolates detected in this publication showed that all of these isolates could be grouped into one group. On the other hand, phylogenetic analysis based on CP amino acid sequence of 18 CCYV isolates from GenBank database showed that all of these isolates could be grouped into two distinct monophyletic clades according to geographic distribution, i.e. Iran isolates for Group Ⅱ and other Asian isolates for GroupⅠ. The CCYV isolates from the Asia show very low genetic diversity in genome.