An Evidence for Host Translation Inhibitory Factor Encoded in a Polydnavirus,Cotesia glomerata Bracovirus,Genome and Its Expression in Parasitized Cabbage White Butterfly,Pieris rapae

Polydnavirus is a DNA virus symbiotic to some endoparasitic wasps and plays a critical role in accomplishing successful parasitic life cycle of host wasps. Host translation inhibitory factor (HTIF) has been found in some polydnaviral genomes and performs parasitic functions leading to host immunosuppression and redirecting host nutrient usage to wasp development. The cabbage white butterfly, Pieris rapae, parasitized by a gregarious endoparasitoid, Cotesia glomerata, undergoes several physiological alterations including immune malfunctioning and failure of pupal metamorphosis. C. glomerata possesses its own symbiotic polydnavirus, C. glomerata bracovirus (CgBV). Its genome consisted of at least 12 segments in unequal amounts. Parasitized P. rapae hemolymph contained HTIF-like protein, which was determined through an immunoblotting assay using HTIF antibody of C. plutellae bracovirus (CpBV). RT-PCR using HTIF primers of CpBV produced an HTIF-like gene in P. rapae larvae parasitized by C. glomerata. Also, this HTIF-like gene was encoded in CgBV genome and its partial sequence of CgBV showed highly homology (98.5%) to amino acid sequence of an HTIF of CpBV, called CpBV15a. These results suggest that a common HTIF-like moiety may be shared among Cotesia-associated bracovirus.