Identification of β-chain of Fo F1 -ATPase in apoptotic cell population induced by Microplitis bicoloratus bracovirus and its role in the development of Spodoptera litura.

Two physiological changes of Spodoptera litura parasitized by Microplitis bicoloratus are hemocyte-apoptosis and retarded immature development. β-Chain of Fo F1 -ATPase was found from a S. litura transcriptome. It belongs to a conserved P-loop NTPase superfamily, descending from a common ancestor of Lepidopteran clade. However, the characterization of β-chain of ATPase in apoptotic cells and its involvement in development remain unknown. Here, the ectopic expression and endogenous Fo F1 -ATPase β-chain occurred on S. litura cell membrane: in vivo, at the late stage of apoptotic hemocyte, endogenous Fo F1 -ATPase β-chain was stably expressed during M. bicoloratus larva development from 4 to 7 days post-parasitization; in vitro, at an early stage of pre-apoptotic Spli221 cells by infecting with M. bicoloratus bracovirus particles, the proteins were speedily recover expression. Furthermore, endogenous Fo F1 -ATPase β-chain was localized on the apoptotic cell membrane. RNA interference (RNAi) of Fo F1 -ATPase β-chain led to significantly decreased head capsule width. This suggested that Fo F1 -ATPase β-chain positively regulated the development of S. litura. The RNAi effect on the head capsule width was enhanced with parasitism. Our research found that Fo F1 -ATPase β-chain was expressed and localized on the cell membrane in the apoptotic cells, and involved in the development of S. litura.