小麦黄花叶病毒(WYMV)2个山东分离物的全基因组序列及进化分析

Evolutional analysis of two new isolates of Wheat yellow mosaic virus from Shandong Province,China

利用5'RACE结合一步法RT-PCR分别从山东泰安与临沂冬小麦上克隆了小麦黄花叶病毒(Wheat yellow mosaic virus,WYMV)的全基因组序列。这2个分离物(TADWK和LYJN)基因组间核苷酸一致性分别为97.21%(RNA1)和95.12%(RNA2)。通过对目前已报道的共14个分离物的基因组不同部分的分析,表明5'UTR是WYMV基因组变化幅度最大的区域,而编码区(ORF)及3'UTR的序列一致性较高且变动幅度小。另外,发现LYJN RNA2的5'UTR与已报道的所有分离物RNA2的核苷酸一致率仅为90%左右。综合分析RNA1和RNA2的系统发生树,表明WYMV各基因组片段呈单独进化特征,不同分离物间存在RNA重排。RNA重组分析显示在LYJN RNA1和TADWK RNA2发现了RNA重组。此研究说明WYMV在山东地区存在分离物分化现象,WYMV的5'UTR是基因组中的突变热点。

Genome sequence of Wheat yellow mosaic virus （WYMV） isolated from Tai′an city and Linyi city in Shandong province of China were determined using one-step RT-PCR and 5′RACE. Sequence identities between these two isolates （TADWK and LYJN） were 97.21% for RNA1 and 95.12% for RNA2 at the nucleotide level. Furthermore, sequence identities of genome, 5′UTR,ORFs, and 3′UTR between these two isolates and other reported twelve isolates were analyzed, suggesting that 5′UTR was the most variable region within WYMV genome, whereas ORFs and 3′UTR were relative stable with a low efficiency of mutation. In addition, nucleotide identities on 5′UTR were only about 90% between LYJN and other thirteen isolates. Phylogenetic trees on RNA1 and RNA2 showed that RNA1 and RNA2 of WYMV were evolved individually and RNA reassortment occurred among different isolates.Meanwhile, RNA recombination events were detected in LYJN RNA1 and TADWK RNA2 as well as several other isolates. Conclusively, this study revealed the evolutional diversification of WYMV isolates in Shandong province, and also indicated that 5′UTR was the mutation hotspot within WYMV.