Determining the nucleotide sequence and capsid-coding region of himetobi P virus: a member of a novel group of RNA viruses that infect insects.

Abstract

We determined the complete genome sequence of Himetobi P virus (HiPV), an insect picorna-like virus, which was isolated from the small brown planthopper, Laodelphax striatellus. The genome of HiPV consists of 9,275 nucleotides excluding the poly (A) tail, and contains two large open reading frames (ORFs), which were separated by a 176-nucleotide noncoding region. The deduced amino acid sequence of the first ORF contains core motifs of picornaviral helicase, protease, and RNA-dependent RNA polymerase. The capsid protein-coding region was mapped onto the second ORF by determining the N-terminal amino acid sequences of the capsid proteins. Subgenomic RNA for the capsid protein gene was not detected in the infected tissue. The capsid protein precursor gene of HiPV lacks an AUG initiation codon at the expected position and the upstream sequence of the gene is predicted to form several stem-loop structures, suggesting that the precursor is produced by internal ribosome entry site (IRES) mediated-translation, as occurs in Plutia stali intestine virus (PSIV). These characteristics of the HiPV genome are similar to those of a new group of RNA viruses consisting of Drosophila C virus (DCV), Rhopalosiphum padi virus (RhPV), and PSIV.