摘要：

为了挖掘稻曲病菌中的真菌病毒资源,深入解析新型真菌病毒基因组结构与功能的关系,以分离自海南省的一株表型异常的稻曲病菌菌株Uv321为研究对象,在前期宏转录组数据的基础上,鉴定该菌株中存在的新型真菌病毒的种类,并围绕着该新型真菌病毒开展了一系列的研究。结果表明,在菌株Uv321中鉴定到一种新型真菌病毒,命名为Ustilaginoidea virens botourmiavirus 7(UvBV7)。UvBV7基因组为正单链RNA(+ssRNA),全长2 406 nt,GC含量为53.78%,包含一个编码RNA依赖的RNA聚合酶(RdRP)的开放阅读框(ORF),该ORF编码643个氨基酸,分子量约为72.727 ku。病毒末端二级结构预测表明,UvBV7的5'和3'末端的碱基均互补配对,形成发夹结构。BlastP比对表明,UvBV7与隶属于葡萄孢欧尔密病毒科、Botoulivirus病毒属的病毒Erysiphe necator associated ourmia-like virus 72有着最高的相似度,但仅为44.52%。基于UvBV7及其他相似病毒的RdRP序列的多重比对结果表明,UvBV7与葡萄孢欧尔密病毒科成员的RdRP氨基酸序列存在8个保守结构域,并在第Ⅵ保守结构域中发现GDD基序,这是病毒RdRP蛋白典型的高度保守核心基序;基于病毒RdRP氨基酸序列构建的系统发育树的结果也表明,UvBV7与隶属于Botoulivirus属的成员聚集成一簇。因此,UvBV7是隶属于葡萄孢欧尔密病毒科、Botoulivirus属的一种新型真菌病毒。稻曲病菌不同菌株的对峙培养结果表明,UvBV7可在营养体亲和的菌丝间进行水平传播,但菌丝尖端-利巴韦林法、高温-利巴韦林法和原生质体再生-利巴韦林法处理均不能将菌株Uv321中的真菌病毒UvBV7脱除。综上所述,本研究不仅丰富了稻曲病菌中真菌病毒的多样性,也为稻曲病的生物防治提供了潜在的低毒力生防因子。

关键词: 稻曲病, 真菌病毒, +ssRNA, 葡萄孢欧尔密病毒科, Botoulivirus属

Abstract:

In order to excavate the mycovirus resources in Ustilaginoidea virens and deeply analyze the relationship between the genome organization and function of a novel mycovirus,it took a U.virens strain Uv321 with abnormal phenotype,isolated from Hainan Province,as the research object,and identified the species of the novel mycovirus in the strain Uv321 on the basis of the previous meta-transcriptome data,a series of studies have been carried out around the novel mycovirus.The results showed that a novel mycovirus was identified in strain Uv321,named Ustilaginoidea viruses botourmiavirus 7 (UvBV7).The genome of UvBV7 is positive single-stranded RNA(+ssRNA),with a total length of 2 406 nt and a GC-content of 53.78%,containing an open reading frame(ORF)encoding RNA-dependent RNA polymerase(RdRP),which encodes 643 amino acids with a molecular weight of about 72.727 ku.The prediction of the protein secondary structure of the viral terminal showed that the 5' and 3' terminal bases of UvBV7 were complementary and paired,forming a hairpin structure.The BlastP alignment showed that UvBV7 had the highest similarity with the virus Erysiphe necator associated ourmia-like virus 72,which belonged to the genus Botoulivirus in the family Botourmiaviridae,but only 44.52%.The multiple alignment results based on the RdRP sequences of UvBV7 and other similar viruses showed that there were 8 conserved domains in the RdRP amino acid sequences of UvBV7 and the members of the family Botourmiaviridae.The GDD motif was found in the Ⅵ conserved domain,which is the typical highly conserved core motif of viral RdRP proteins.The phylogenetic tree constructed based on the amino acid sequence of the viral RdRP also indicated that UvBV7 clustered with the members belonging to the genus Botoulivirus.Therefore,UvBV7 is a novel mycovirus belonging to the genus Botoulivirus in the family Botourmiaviridae.The results of dual cultures of different strains of U.virens showed that UvBV7 could be transmitted horizontally between vegetative compatibility strains,but the mycelial tip-ribavirin,heat-ribavirin and protoplast regeneration-ribavirin treatments were unable to eliminate the mycovirus UvBV7 in strain Uv321.In conclusion,this study not only enriched the diversity of mycoviruses in U.virens,but also provided potential biocontrol agents with hypovirulence for the biocontrol of rice false smut.

Key words: Rice false smut, Mycovirus, +ssRNA, Botourmiaviridae, Botoulivirus