A putative actin destabilizer, CpBV-RTX, encoded in Cotesia plutellae bracovirus and its expression in the parasitized Plutella xylostella

A novel gene was identified in Cotesia plutellae bracovirus (CpBV). It was encoded in an endoparasitoid wasp, C. plutellae, and its symbiotic virus, CpBV, genomes but not in its natural host, Plutella xylostella, genome. The gene has an open reading frame of 94 amino acid sequence. A bioinformatic analysis indicates that the gene has a signal peptide of 18 residues at amino terminus and 4 glycosylation sites at threonine, serine, and two asparagine residues. The gene expression was specific in parasitized P. xylostella by C. plutellae, not in nonparasitized larvae. In parasitized larvae, it was expressed at the first day after parasitization and resumed its expression on the fourth day. Its expression showed tissue specificity at fat body/epidermis, but not at hemocyte and gut among tested tissues. Its sequence showed some similarity with a bacterial toxin, RTX of Vibrio spp. especially in its actin cross-linking domain. The viral gene has been named as CpBV-RTX. Its putative physiological function was discussed in terms of host-parasite molecular interactions.