Characterization of a protein tyrosine phosphatase gene CvBV202 from Cotesia vestalis polydnavirus (CvBV)

Cotesia vestalis (Haliday) (Hymenoptera: Braconidae) is an endoparasitoid of the larval stage of the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae) and injects a polydnavirus (CvBV) into its host during oviposition. In this paper we characterize CvBV202 and its product. CvBV202 is located on segment S2 of CvBV genome; it has a size of 984 bp and encodes a putative protein of 328 amino acids, including protein phosphatase domain and tyrosine-specific protein phosphatase domain. Gene transcripts were detected in extracts of the host as early as 2 h post-parasitization (p.p.) and continued to be detected for 6 days. Tissue-specific patterns of this gene expression showed that CvBV202 had a close relationship with the host's physiological alternations including immunosuppression, modulation of hormone titer, and nutrition metabolism. The protein was detected in the parasitized hosts at 12 h p.p. using western blot assay. The product of CvBV202 was found to be around 59 kDa, much larger than the predicted molecular weight of 37.8 kDa, suggesting that post-translational modification of CvBV202 occurs in host cells, corresponding with the existence of many post-translational modification sites. Immunofluorescence staining and confocal laser scanning microscopy revealed that CvBV202 and the fused protein eGFP-CvBV202 were observed both in the nuclear region and cytoplasm of the hemocytes of the naturally parasitized host larvae and rBac-eGFP-CvBV202-infected Tn-5B1-4 cells, respectively.