The complete genomic sequence of a novel mycovirus from Rhizoctonia solani AG-1 IA strain B275
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ANNOTATED SEQUENCE RECORD
The complete genomic sequence of a novel mycovirus from Rhizoctonia solani AG-1 IA strain B275 Li Zheng • Huiquan Liu • Meiling Zhang Xiong Cao • Erxun Zhou
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Received: 24 October 2012 / Accepted: 8 January 2013 / Published online: 27 February 2013 Ó Springer-Verlag Wien 2013
Abstract The complete genome of a novel mycovirus, Rhizoctonia solani dsRNA virus 1 (RsRV1) was sequenced and analyzed. It is composed of two dsRNA genome segments, 2379 bp and 1811 bp in length, which were referred to as RsRV1-1 and RsRV1-2, respectively. RsRV1-1 contains a single open reading frame (ORF1), which has a conserved RNA-dependent RNA polymerase (RdRp) domain, whereas RsRV1-2 contains a single ORF2, which might encode a multifunctional protein. The genome organization of RsRV1 is similar to that of members of the family Partitiviridae. However, phylogenetic analysis indicated that RsRV1 formed a distinct clade together with three other unclassified viruses, suggesting that RsRV1 may belong to a new family of dsRNA mycoviruses. This is the first report of the full-length nucleotide sequence of a novel dsRNA mycovirus, RsRV1, infecting R. solani AG-1 IA strain B275, the causal agent of rice sheath blight.
Introduction The basidiomycete fungus Rhizoctonia solani Ku¨hn [teleomorph: Thanatephorus cucumeris (Frank) Donk] is a notorious soil-borne plant pathogen and exhibits a wide host range that includes rice, maize, potato, peanut, soybean, alfalfa, vegetables, ornamental plants, and forest and fruit trees [12]. Rhizoctonia solani is considered a L. Zheng M. Zhang X. Cao E. Zhou (&) Department of Plant Pathology, South China Agricultural University, Guangzhou, Guangdong 510642, China e-mail: [email protected] H. Liu Department of Plant Pathology, Northwest A & F University, Yangling, Shanxi 712100, China
collective species, consisting of at least 14 genetically isolated anastomosis groups (AGs) defined by their hyphal interactions [2, 4, 11]. Double-stranded RNAs (dsRNAs) are commonly detected in natural populations of R. solani isolates AG-2 to -13 [1]. Members of the genus Partitivirus have been detected, and a complete molecular characterization of the genome of a partitivirus from R. solani has been published [14]. Indirect evidence suggested that the 3.6-kbp (M2) and 6.4-kbp (M1) dsRNAs are associated with diminished or enhanced virulence in R. solani [5]. Studies have also shown that quinic acid can induce hypovirulence and expression of a hypovirulence-associated dsRNA in R. solani [7]. Although some progress has been made, little is known about the genetic content of numerous dsRNAs found in R. solani because most dsRNA mycoviruses infect R. solani asymptomatically [6, 18]. In the present study, a novel unclassified dsRNA mycovirus, R. solani dsRNA virus 1 (RsRV1), was isolated from R. solani AG-1 IA strain B275, the causal agent of rice sheath blight. Phylogenetic analysis of the deduced amino acid sequence of the putative RNA-dependent RNA polymerase (RdRp) suggested that RsRV1 is closely
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