A new dicistro-like virus from soldier fly, Inopus flavus (Diptera: Stratiomyidae), a pest of sugarcane

Abstract

The native Australian soldier flies, Inopus spp. (Diptera: Stratiomyidae), are agricultural pests of economic importance to the sugarcane industry. While adult soldier flies do not feed on sugarcane, larvae spend one to two-years underground feeding on roots, causing mechanical and systemic damage to crops (Saccharum officinarum L.) that impacts yield. Current measures of pest control commonly target above ground pests and are ineffective against solider fly larvae, highlighting the importance of novel control methods. A screen of the salivary gland transcriptome of Inopus flavus (James) revealed the presence of viral RNA belonging to a potentially novel member of the Dicistroviridae family. Viruses from this family have been found naturally infecting insects from a range of taxonomic groups and they often cause pathogenesis in their hosts. To characterise the genetic and physical properties of the new virus, the positive RNA genome was analysed using a combination of sequencing approaches. The virus genome is organised similarly to members of the Dicistroviridae with two open reading frames (ORF) the first encoding non-structural proteins and the second encoding structural proteins. The genome includes two potential internal ribosomal entry sites (IRES) one within the 5' UTR and the other in the intergenic region (IGR). Based on the amino acid sequences of the non-structural and structural polyproteins encoded by the two ORF soldier fly virus groups within the dicistrovirus family. Virus particles purified from infected larvae and visualised by electron microscopy are icosahedral, non-enveloped, and 30 nm in diameter. The genetic and physical characteristics of this novel soldier fly virus are consistent with it being a member of the Dicistroviridae.

Transcriptome Analysis Reveals a Diverse Range of Novel Viruses in Australian Sugarcane Soldier Fly (Inopus flavus) Larvae

“… * These viruses were previously reported by Asselin et al (2021) [ 13 ] and Colmant et al (2022) [ 14 ]. …”

“…With these reads, we identified several RNA virus sequences from the Narnaviridae , Totiviridae , Partitiviridae , Orthomyxoviridae and Xinmoviridae families in soldier fly salivary glands. We also identified viral sequences from the Dicistroviridae and the currently unclassified flavi-like jingmenvirus genus in our datasets ( Table 1 ), but these have been reported previously [ 13 , 14 ]. In addition, we found the full genome sequence of a non-enveloped single-stranded DNA virus from the Parvoviridae family.…”

“…In this study, we used total RNA sequencing to investigate the virome of soldier fly larvae. Previously, employing this approach, we described the identification of a novel dicistro-like virus [ 13 ] and a novel jingmenvirus [ 14 ] in our RNA-Seq data. Subsequently, we expanded our analysis to further explore the presence of additional viral sequences.…”