title: Characterization of a novel bipartite double-stranded RNA mycovirus conferring hypovirulence in the phytopathogenic fungus Botrytis porri.
abstract: The ascomycete Botrytis porri causes clove rot and leaf blight of garlic worldwide. We report here the biological and molecular features of a novel bipartite double-stranded RNA (dsRNA) mycovirus named Botrytis porri RNA virus 1 (BpRV1) from the hypovirulent strain GarlicBc-72 of B. porri. The BpRV1 genome comprises two dsRNAs, dsRNA-1 (6,215 bp) and dsRNA-2 (5,879 bp), which share sequence identities of 62 and 95% at the 3'- and 5'-terminal regions, respectively. Two open reading frames (ORFs), ORF I (dsRNA-1) and ORF II (dsRNA-2), were detected. The protein encoded by the 3'-proximal coding region of ORF I shows sequence identities of 19 to 23% with RNA-dependent RNA polymerases encoded by viruses in the families Totiviridae, Chrysoviridae, and Megabirnaviridae. However, the proteins encoded by the 5'-proximal coding region of ORF I and by the entire ORF II lack sequence similarities to any reported virus proteins. Phylogenetic analysis showed that BpRV1 belongs to a separate clade distinct from those of other known RNA mycoviruses. Purified virions of ~35 nm in diameter encompass dsRNA-1 and dsRNA-2, and three structural proteins (SPs) of 70, 80, and 85 kDa, respectively. Peptide mass fingerprinting analysis revealed that the 80- and 85-kDa SPs are encoded by ORF I, while the 70-kDa SP is encoded by ORF II. Introducing BpRV1 purified virions into the virulent strain GarlicBc-38 of B. porri caused derivative 38T reduced mycelial growth and hypovirulence. These combined results suggest that BpRV1 is a novel bipartite dsRNA virus that possibly belongs to a new virus family.
authors.affiliation: The State Key Laboratory of Agricultural Microbiology and The Key Laboratory of Plant Pathology of Hubei Province, Huazhong Agricultural University, Wuhan, Hubei, China.
authors.forename: Mingde
authors.initials: M
authors.lastname: Wu
authors.forename: Fengyin
authors.initials: F
authors.lastname: Jin
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Long
authors.initials: L
authors.lastname: Yang
authors.forename: Daohong
authors.initials: D
authors.lastname: Jiang
authors.forename: Guoqing
authors.initials: G
authors.lastname: Li
mesh_terms: D000595:Amino Acid Sequence; D020171:Botrytis / Q000472:pathogenicity* / Q000502:physiology / Q000821:virology*; D005737:Garlic / Q000382:microbiology* / Q000821:virology; D016679:Genome, Viral; D008969:Molecular Sequence Data; D010802:Phylogeny; D010935:Plant Diseases / Q000382:microbiology* / Q000821:virology; D012328:RNA Viruses / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D012330:RNA, Double-Stranded / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012367:RNA, Viral / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014774:Virulence
chemical_list: D012330:RNA, Double-Stranded; D012367:RNA, Viral; D014764:Viral Proteins