Siratro latent polerovirus (SLPV): a new polerovirus from Australia with a non-functional open reading frame 0

Abstract

Macroptilium atropurpureum (siratro) samples from Queensland, Australia were collected as part of virus surveys and screened using tissue blot immunoassays for the presence of luteoviridae viruses. Sequencing of a reverse transcription polymerase chain reaction (RT-PCR) product, generated with degenerate primers for poleroviruses, revealed the non-symptomatic virus in siratro was a novel polerovirus, given the proposed name siratro latent polerovirus (SLPV). SLPV-specific RT-PCR showed that SLPV was widely distributed in siratro throughout Queensland. SLPV was transmitted via Aphis craccivora (cowpea aphids) to siratro and Pisum sativum (field pea). The complete genome of one isolate of SLPV was found to be 6090 nucleotides in length and shared only 69% nucleotide identity with its closest match, phasey bean mild yellows virus. Poleroviruses contain six major open reading frames (ORFs) labelled ORF 0–5. The SLPV genome has a similar arrangement. However, the region that should encode for ORF 0 is missing an AUG start codon. Sequencing of this region, from eight SLPV isolates, from different geographic regions, showed all lacked the ORF 0 AUG site and some isolates contained point mutations and deletions in this region, thus inhibiting translation of ORF 0. These results suggest that SLPV does not have a functional ORF 0 which may affect viral pathogenicity and restrict host range. This is the first report, to date, of a polerovirus with an apparently non-functional ORF 0 region.