Detection And Sequence Analysis Of Three RNA Mycoviruses In Nigrospora Oryae Strain CS-1

Mycovirus is one kind of viruses hosting in the fungi.The infection way of the mycoviruses has two kinds:single virus infection and multi-virus mixed infection. Usually mixed infection is in the majority. Some fungi infected with the virus have some symptoms,and others appear implicit phenomenon. Some mycoviruses can enhance the ability of adaptation to the environment,some viruses can slow down the growth rate of the host fungi,reduce the amount of spore,weaken the pathogenicity, and show low toxicity.The rice brown streak leaf spot is a kind of disease caused by Nigrospora oryzae. The disease mainly appeared on leaves in the late stage of rice growth,resulting in the decline of filled rice seed rate, and seriously affecting the heading. In Southern China, the incidence of the disease is gradually expanding, with increasing economic loss. In order to explore a new way to prevent the diseases, this study was carried out to study possible virus existence in the pathogenic fungus and the effect of virus on the host fungus. In this paper, we used the N. oryzae strain CS-1 as the material to detect the virus. The genome sequence and bioinformatics analysis were carried out to obtain the following results:1) Three RNA bands were detected in the fungus CS-1, by using cellulose CF adsorption separation and agarose gel electrophoresis. The bands showed the high content of RNA and the diversity of RNA. The bands were designated as RNA-L, RNA-M, RNA-S respectively in order of the size of molecular.2)The whole genome sequencing of 5 Kb RNA-L was carried out and analyzed by bioinformatics software.Sequence analysis revealed that RNA-L has a genomic structrue characteristic of the Totiviridae family, and contains 2 overlapping ORFs.It predicted that the victorivirus belonging to the family terminates the re start of the key sequence elements of the structure of the key components.And the respective ORF encoding protein victoriae virus 190S Helminthosporium (HvV 190) is the virus of CP and RdRp showed the highest similarity. Phylogenetic analysis indicates that the virus is a member of the victorivirus genus, which is named oryae victorivirus Nigrospora 2(NoRV2).3)Whole genome sequencing of a 3KB RNA-S showed that this fragment has characteristics of the genome structure of mitochondrial virus family. Sequence alignment revealed that the ORF encoding product of RNA-S has a typical conserved motif of mitochondrial virus RdRp. We nameRNA-Sas Nigrospora oryae mitovirus 1 (NoMV1).4)Sequence of the 3kb RNA-Malso has the typical of the genome structure of the mitochondrial genome.In this paper, it is the first time to find that both of Totiviridae and mitoviruses virus exist in N. oryzae.We have taken the whole genome sequence out,enriched the diversity of the fungal species inN. oryzae.The further experiment will conduct to verify the effect of the virus(es) on the host and get new material for biological control of rice leaf brown streak disease by constructing the full-length cDNA infectious clone.