A novel betapartitivirus RnPV6 from Rosellinia necatrix tolerates host RNA silencing but is interfered by its defective RNAs.
The family Partitiviridae comprises of five genera with bi-segmented dsRNA genomes that accommodate members infecting plants, fungi or protists. All partitiviruses with only a few exceptions cause asymptomatic infections. We report the characterization of a novel betapartitivirus termed Rosellinia necatrix partitivirus 6 (RnPV6) from a field isolate of a plant pathogenic fungus, white root rot fungus. RnPV6 has typical partitivirus features: dsRNA1 and dsRNA2 are 2462 and 2499bps in length encoding RNA-dependent RNA polymerase and capsid protein. Purified particles are spherical with a diameter of 30nm. Taking advantage of infectivity as virions, RnPV6 was introduced into a model filamentous fungal host, chestnut blight fungus to investigate virus/host interactions. Unlike other partitiviruses tested previously, RnPV6 induced profound phenotypic alterations with symptoms characterized by a reduced growth rate and enhanced pigmentation and was tolerant to host RNA silencing. In addition, a variety of defective RNAs derived from dsRNA1 appear after virion transfection. These sub-viral RNAs were shown to interfere with RnPV6 replication, at least for that of cognate segment dsRNA1. Presence of these sub-viral elements resulted in reduced symptom expression by RnPV6, suggesting their nature as defective-interfering RNAs. The features of RnPV6 are similar to but distinct from those of a previously reported alphapartitivirus, Rosellinia necatrix partitivirus 2 that is susceptible to RNA silencing.
Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki 710-0046, Japan. Electronic address: chiba@nuagr1.agr.nagoya-u.ac.jp.
Sotaro
S
Chiba
Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki 710-0046, Japan. Electronic address: yu-hsin.lin@hb.nagase.co.jp.
Yu-Hsin
YH
Lin
Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki 710-0046, Japan. Electronic address: hkondo@okayama-u.ac.jp.
Hideki
H
Kondo
Institute of Fruit Tree Science, National Agriculture and Food Research Organization (NARO), Morioka, Iwate 020-0123, Japan. Electronic address: satokok@affrc.go.jp.
Satoko
S
Kanematsu
Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki 710-0046, Japan. Electronic address: nsuzuki@okayama-u.ac.jp.
Nobuhiro
N
Suzuki
D001203:Ascomycota / Q000235:genetics* / Q000821:virology*; D001483:Base Sequence; D000067148:Fungal Viruses / Q000235:genetics*; D015967:Gene Expression Regulation, Viral; D020868:Gene Silencing; D016679:Genome, Viral; D010802:Phylogeny; D034622:RNA Interference; D012331:RNA, Fungal / Q000235:genetics*; D012367:RNA, Viral / Q000235:genetics*; D014158:Transcription, Genetic
D012331:RNA, Fungal; D012367:RNA, Viral
Cryphonectria parasitica; Defective RNA; Partitivirus; RNA silencing; Rosellinia necatrix; dsRNA virus