2.5-fold expansion of the genetic diversity of blunerviruses through plant (meta)transcriptome data-mining

Abstract

Kitaviruses are plant-infecting, non-systemic disease-causing viruses with multipartite single-stranded RNA genomes. Despite their importance, knowledge on kitaviruses is limited in comparison with other plant virus groups, mainly because of the lesser number of identified and characterized kitaviruses and their isolates. In the present study, we explored plant (meta)transcriptome data available in public domain and identified genome sequences of fifteen putative novel blunerviruses in fifteen plant species, including three gymnospermic and three monocot species. Four RNA segments (RNAs 1–4) of ten identified viruses were recovered, whilst atleast two RNA segments were recovered for the remaining viruses. Monocistronic RNA1 of identified viruses encodes methyltransferase (MET)-helicase (HEL) polyprotein, except RNA1 of Nanmu blunervirus 1 that encodes a relatively larger MET-HEL-RNA-dependent RNA polymerase (RdRp) polyprotein. Monocistronic RNAs 2 and 4, respectively of identified viruses, encode HEL-RdRp polyprotein and movement protein (MP). Three to four open reading frames (ORFs) were determined in RNA3 of identified viruses, of which the relatively conserved ORF3, always encodes the negevirus membrane protein (SP24) homolog. Phylogenetic analysis grouped the identified viruses with known blunerviruses. Based on genome organization, sequence identities of encoded proteins with known blunerviruses and phylogeny, the identified viruses are regarded as new members of the genus Blunervirus. The study paves way for initiating further studies on understanding the biological properties, economic importance and geographical distribution of identified blunerviruses.