Structure and Expression Profiles of Two Putative Cotesia plutellae Bracovirus Genes (CpBV-H4 and CpBV-E94a) in Parasitized Plutella xylostella

Endoparasitoid wasp, Cotesia plutellae, parasitizes diamondback moth, Plutella xylostella, and interrupts host development and immune processes. Its obligate symbiotic virus, C. plutellae bracovirus (CpBV), has been regarded as a major source of interrupting the physiological alteration during the parasitization. On the process of genome sequencing of CpBV, two putative genes were detected and homologous to E94 of baculovirus and histone H4 subunit of a nucleosome, respectively. The open reading frame of CpBV-E94a was 642 bp encoding 214 amino acid residues, while that of CpBV-H4 was 423 bp encoding 141 amino acid residues. Both genes were on the same segment of CpBV genome. They were expressed only in the P. xylostella parasitized by C. plutellae in which all three tissues of hemo-cytes, fat body, and gut expressed both genes. Quantitative RT-PCR analyses indicated that their expression patterns in the parasitized host were similar and exhibited bimodal peaks at early and late parasitization periods. We discussed their physiological functions based on the gene structures.