Characterization And Biological Function Of Puccinia Striiformis Mitovirus 2

Wheat stripe rust,caused by the obligate biotrophic fungus Puccinia striiformis f.sp.tritici(Pst),seriously affects wheat production.With the next-generation sequencing(NGS)development,an increasing number of mycoviruses have recently been characterized.Recently,it is reported that fungal viruses are able to help wheat stripe rust infect wheat in the interaction.The discovery of novel mycoviruses expands our knowledge of virus taxonomy,ecology and evolution.Here,we report the complete genome sequence and biological characterization of a new mitovirus from strain GS-1 which was designated as “Puccinia striiformis mitovirus 2”(Ps MV2).The main results are as follows.1.Gained contigs of viruses derived from the wheat stripe rust by technology of the viral metagenomics sequencing.Assembled contigs by DNAMAN 8.0 and selected cabdidate virus sequences.We cloned its complete genome by RACE(rapid amplification of c DNA ends)and RT-PCR technology.2.The stem-loop structures of the 5’ and 3’ UTRs of Ps MV2 were predicted using Mfold program.It protected viruse from being damaged by endonuclease in mitochondrion.Furthermore,multiple protein sequence alignment suggested that the predicted Rd Rp domain contains the six conserved motifs.3.Phylogenetic analysis revealed that Ps MV2 clustered with members of the genus Unuamitovirus and was phylogenetically closest to Cr MV1.Taken together,Ps MV2 belongs to the genus Unuamitovirus within the family Mitoviridae.4.To investigate the expression pattern of Ps MV2 during Pst infection stages quantitative RT-PCR(q RT-PCR)was used.Results indicated that Ps MV2 is highly induced at early stages of Pst race CYR31 infection and induced a higher transcription level.We used the transient expression method mediated by A.tumefaciens to verify the ability of Ps MV2 to suppress Bax-triggered PCD,which is similar to the defense-related HR in plant cells5.By BSMV mediated gene silencing(BSMV-HIGS)technology,I temporarily silenced Ps MV2 in the affinity strain CYR31,comparing to control which not silenced target genes Ps MV2,the interaction of silenced CYR31 with the wheat resulted in increased accumulation of reactive oxygen species(ROS),restricted hyphae area and the mycelia growth,inferring the reduced pathogenicity of Pst.The results showed that Ps MV2 was able to promote the virulence of its fungal host and demonstrate the positive effect of Ps MV2 toward Pst virulenceIn summary,this study reporte a noval +ss RNA mitovirus from wheat strip rust.We clear its genome structure and ascertain its taxonomic status.Besides,the results primarily illustrate biological effects that Ps MV2 promote host pathogenicity in Pst.This study enriches the research on the types and diversity of mycovirus,and will provide theoretical basis for the cultivation of resistant varieties.