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), which acts as a symbiotic virus of the endoparasitoid wasp C. plutellae. The gene was encoded in the genome of CpBV, but not in the genome of its natural host, Plutella xylostella. The gene has an open reading frame comprised of 94 amino acids. A bioinformatic analysis indicated that the gene encodes a signal peptide comprised of 18 residues at its amino terminus and 4 glycosylation sites at threonine and serine residues, as well as two asparagine residues. The expression of the gene by C. plutellae was specific in parasitized P. xylostella, but not in unparasitized larvae. In parasitized larvae, the expression of the gene occurred on the first day after parasitization, and its expression resumed on the fourth day. The gene showed tissue specific expression in the fat body and epidermis, but not in hemocytes and gut tissue. Its sequence showed some similarity with that of a bacterial toxin, RTX, of Vibrio spp., especially in its actin cross-linking domain. The viral gene has been named CpBV-RTX, and its putative physiological function is discussed in terms of host-parasite molecular interactions.