Characterization of two genes of Cotesia vestalis polydnavirus and their expression patterns in the host Plutella xylostella.

Cotesia vestalis is an endoparasitoid of larval stages of Plutella xylostella, the diamondback moth. For successful parasitization, this parasitoid injects a polydnavirus into its host during oviposition. Here we isolated two genes, which we named CvBV1 and CvBV2. CvBV1 was located on segment CvBV-S5 with a size of 790 bp, while CvBV2 was located on segment CvBV-S51 with a size of 459 bp. A gene copy of CvBV2 was found on segment CvBV-S48, which we name CvBV2'. Gene duplication occurred in both genes, tandem gene duplication for CvBV1 and segmental duplication for CvBV2. Gene transcripts of the two genes were detected in hosts as early as 0.5 h post-parasitization (p.p.) and continued to be detected for six days, and tissue-specific expression patterns showed that they could be detected in the haemolymph and brain at 2 h p.p., suggesting that they could participate in early protection of parasitoid eggs from host cellular encapsulation.