Four Novel Botourmiaviruses Co-Infecting an Isolate of the Rice Blast Fungus Magnaporthe oryzae

Abstract

Via virome sequencing, six viruses were detected from <i>Magnaporthe oryzae</i> strains YC81-2, including one virus in the family <i>Tombusviridae</i>, one virus in the family <i>Narnaviridae</i> and four viruses in the family <i>Botourmiaviridae</i>. Since the RNA-dependent RNA polymerase (RdRp) of one botourmiavirus show the highest identity (79%) with Magnaporthe oryzae ourmia-like virus 1 (MOLV1), the virus that was grouped into the genus <i>Magoulivirus</i> was designated as Magnaporthe oryzae botourmiavirus 2 (MOBV2). The three other novel botourmiaviruses were selected for further study. The complete nucleotide sequences of the three botourmiaviruses were determined. Sequence analysis showed that virus 1, virus 2, and virus 3 were 2598, 2385, and 2326 nts in length, respectively. The variable 3' untranslated region (3'-UTR) and 5'-UTR of each virus could be folded into a stable stem-loop secondary structure. Each virus consisted of a unique ORF encoding a putative RdRp. The putative proteins with a conserved GDD motif of RdRp showed the highest sequence similarity to RdRps of viruses in the family <i>Botourmiaviridae</i>. Phylogenetic analysis demonstrated that these viruses were three distinct novel botourmiaviruses, clustered into the <i>Botourmiaviridae</i> family but not belonging to any known genera of this family. Thus, virus 1, virus 2, and virus 3 were designated as Magnaporthe oryzae botourmiavirus 5, 6, and 7 (MOBV5, MOBV6, and MOBV7), respectively. Our results suggest that four distinct botourmiaviruses, MOBV2, MOBV5, MOBV6, and MOBV7, co-infect a single strain of <i>Magnaporthe oryzae</i>, and MOBV5, MOBV6, and MOBV7 are members of three unclassified genera in the family <i>Botourmiaviridae</i>.