A novel toti-like virus from a plant pathogenic oomycete Globisporangium splendens.

We investigated virus infection in the plant pathogenic oomycete Globisporangium splendens, formerly classified as Pythium splendens, in Japan. From 12 strains investigated, three strains contained virus-like double-stranded (dsRNA). Next-generation sequencing revealed that the G. splendens strain MAFF 425508 and MAFF 305867 contained a virus related to toti-like viruses, that we named Pythium splendens RNA virus 1 (PsRV1). PsRV1 has a ca. 5700 nt-length genome encoding two overlapping open reading frames (ORFs). The ORF2 encodes an RNA-dependent RNA polymerase (RdRp). Phylogenetic analysis with deduced RdRp amino acid sequences indicated that PsRV1 was closely related to Pythium polare RNA virus 1 (PpRV1) from G. polare infecting mosses in the Arctic. PsRV1 was vertically transmitted through the hyphal swellings, vegetative organs of G. splendens, in a temperature-dependent manner. Also, we showed that PsRV1 infected in a symptomless manner.

Genome sequence of a novel partitivirus identified from the oomycete Pythium nunn.

The mycoparasitic oomycete Pythium nunn isolate UZ415 contains two double-stranded RNAs (dsRNAs) of different sizes. The 1707-nt dsRNA1 and the 1475-nt dsRNA2 potentially encode an RNA-dependent RNA polymerase (RdRp) and a coat protein (CP), respectively, with sequence similarity to the RdRp and CP of gammapartitiviruses (< 57% and < 36%). Phylogenetic analysis of the deduced RdRp amino acid sequences indicated that the virus identified from P. nunn is classifiable as a distinct member of the genus Ganmmapartitivirus in the family Partitiviridae. This virus isolate is hereby named Pythium nunn virus 1 (PnV1).