侵染葱鳞葡萄孢的一种新型dsRNA病毒

A novel dsRNA mycovirus infecting the phytopathogenic fungus Botrytis squamosa

测定了葱鳞葡萄孢（Botrytissquamosa）菌株LeekBc-10和GarlicBc-2的菌丝生长速度、致病力和菌株LeekBc-10中一种dsRNA病毒的eDNA序列及其推定编码的蛋白质序列，并对该病毒进行了系统进化分析。结果表明：菌株OarlicBc-2菌丝生长较快、致病力较强，菌株LeekBc-10菌丝生长较慢、致病力较弱。菌株Leek-Bc-10菌丝中有2条dsRNA片段（dsRNA-1和dsRNAu2），序列测定表明：dsRNA-1和dsRNA-2核苷酸序列与相对应BotrytisporriRNAvirus1（BpRV1）中2条dsRNA片段的相似性分别为91．7％和97．7％，故可判断菌株LeekBc-10中的dsRNA是一种真菌病毒，暂时命名为BotrytissquareosaRNAvirus1（BsRV1）。BsRV1中dsRNA-1和dsRNA-2分别含有一个大的开放阅读框（ORF），即ORFⅠ和ORFⅡ，各自编码长度为1901和1788个氨基酸的假定蛋白，且分别与BpRV1中的对应假定蛋白的相似度为97．1％和98．7％。对BsRVlORFl编码的假定蛋白的分析表明：该蛋白含有RdRp-4（RNAdependemRNApolymerase）超家族蛋白的保守结构域。BsRVl的RdRp与Totiviridae、Chrysoviridae和Megabirnaviridae等科病毒的RdRp同源性为19％～23％，且具有上述病毒RdRp的8个保守结构域。系统发育分析表明：BsRVl与BpRVl聚在一起形成一个独立分支，属于同一种病毒，且不能归到任何已有的病毒科中，因而可能代表一个新的病毒科。

The growth rate and pathogenicity of strains LeekBc-10 and GarlicBc-2 of Botrytis squa- mosa have been determined in this study. Double stranded RNAs （dsRNAs） in strain LeekBc-10 were eDNA cloned and the resulting eDNA sequences were used to infer proteins and taxonomic status. The results showed that the strain LeekBc-10 was inferior in growth on potato dextrose agar and more vul- nerable to infection of garlic leaves, compared to the strain GarlicBc-2. Two dsRNAs, dsRNA-1 and dsRNA-2, were detected in the mycelia of strain LeekBc-10. Sequences of dsRNA-1 and dsRNA-2 are 91.7% and 97.7% identical to the corresponding sequences of dsRNA-1 and dsRNA-2 from Botrytis porri RNA virus 1 （BpRV1）. Therefore, the dsRNAs in the strain LeekBc-10 are the genome of a RNA virus, designated as Botrytis squamosa RNA virus 1 （BsRV1）. Two open reading frames （ORF）, ORF I and ORF II, were predicted on the dsRNA-1 and dsRNA-2 of BsRV1, respectively. They putatively encode two proteins with 1 901 and 1 788 amino acid residues respectively, which were 97. 1% and 98. 7 % similar to the proteins putatively encoded by ORF I and ORF II of BpRV1 respectively. The pro- tein encoded by ORF I of BsRV1 contains the RdRp_4 （_RNA-_dependent _RNA polymerase） superfamily domain. The RdRp of BsRV1 has eight conserved motifs for viruses belonging to Totiviridae, Chryso- viridae and Megabirnaviridae and is 19%-23% identical to those encoded by the viruses in these fami- lies. This study suggests that BsRV1 and BpRV1 belong to the same virus species, possibly represen- ting a novelvirus family.