Identification of a novel member of the genus Laulavirus (family Phenuiviridae) from the entomopathogenic ascomycete fungus Cordyceps javanica

Abstract

The virus family Phenuiviridae (order Bunyavirales, comprising segmented negative-sense single stranded RNA viruses) has highly diverse members that are known to infect animals, plants, protozoans and fungi. In this study, we identified a novel phenuivirus infecting a strain of the entomopathogenic fungus Cordyceps javanica, tentatively named Cordyceps javanica negative-strand RNA virus 1 (CjNRSV1). The CjNRSV1 genome consisted of three negative-sense single stranded RNA segments (RNA1–3) with lengths of 7252, 2401 and 1117 nt, respectively. The 3¢- and 5¢-terminal regions of the RNA1, 2, and 3 segments had identical sequences, and the termini of the RNA segments were complementary to each other, reflecting a common characteristic of viruses in the order Bunyavirales. RNA1 encoded a large protein (~274 kDa) containing a conserved domain for the bunyavirus RNA-dependent RNA polymerase (RdRP) superfamily, with 57–80% identity to the RdRP encoded by phenuiviruses in the genus Laulavirus. RNA2 encoded a protein (~79 kDa) with no conserved domain but showing identity (47–63%) to the movement protein (MP, a plant viral cell-to-cell movement protein)-like protein (MP-L) encoded by RNA2 of laulaviruses. RNA3 encoded a protein (~28 kDa) with a conserved domain for the phenuivirid nucleocapsid protein superfamily. Moreover, in phylogenetic analysis using the RdRPs of various phenuiviruses and other unclassified phenuiviruses, CjNRSV1 was grouped with established members of the genus Laulavirus. Our results suggest that CjNRSV1 is a novel fungus-infecting member of the genus Laulavirus in the family Phenuiviridae.