Identification and characterization of a novel Iflavirus in a stored-product psocid, Liposcelis bostrychophila (Psocodea: Liposcelididae)

Abstract

Liposcelis bostrychophila (Badonnel) is a worldwide stored-product pest that tends to develop resistance to commonly used insecticides rapidly. To control insect pest biologically, insect-specific viruses (ISVs) are considered to be a promising agent, but few ISVs have been reported in stored-product psocids. In this study, a novel iflavirus named Liposcelis bostrychophila iflavirus (LbIFV) was identified. This virus has a genome length of 9,263 nucleotides and was isolated from L. bostrychophila using RNA-Seq technology. The polyprotein of LbIFV contains two picornavirus capsid protein-like domains, an RNA-dependent RNA polymerase (RdRp) domain, an RNA helicase, and a 3C-protease. The virus replicates in its host, and triggers the activation of the host's antiviral immunity, specifically through the small interfering RNA (siRNA)-based mechanism. Phylogenetic analysis showed that LbIFV clustered with Bundaberg bee virus 4, Sacbrood virus, and Darwin bee virus 4, which suggested that LbIFV was presumed to belong to Iflaviridae. LbIFV was transmitted vertically from parent to offspring, and the viral infection rate reached 100%. LbIFV was present at all developmental stages of L. bostrychophila, and it successfully co-existed in this psocid for a long period. The abundance of LbIFV in L. bostrychophila decreased significantly under high temperatures and insecticide exposures. In summary, LbIFV is the first characterized RNA virus in Liposcelis species, and it established stable symbiotic relationships with L. bostrychophila.