Systematic profiling of nudivirus-like genes reveals conserved and differentiated roles in a domesticated endogenous virus

Abstract

Cotesia vestalis bracovirus (CvBV) is a type of domesticated endogenous virus (DEV) derived from ancestral nudiviruses that is integrated into the genome of the parasitoid wasp Cotesia vestalis. The CvBV proviral genome is composed of two distinct components: one encoding genes associated with virion morphogenesis and assembly, and the other harboring virulence genes that are excised, circularized, and packaged into virions. CvBV replication and particle assembly occur exclusively in the ovaries of female wasps. While prior studies have largely focused on the function of virulence genes during parasitization, the molecular mechanisms underlying CvBV replication and assembly remain poorly understood. Here, we identified 71 nudivirus-like genes in the C. vestalis genome through integrated transcriptomic and proteomic analyses. Using gene silencing and microscopy-based imaging approaches, we functionally characterized 24 key genes involved in DNA replication (helicase, integrase-1, and integrase-2), transcriptional regulation (p47, lef-5, and lef-9), capsid formation (vp39, PmV, HzNVorf9–1, HzNVorf9–2, HzNVorf106, 38k, 27b, and K425_459), envelope formation (11k, 17a-1, 35a-1, 35a-2, and K425_461), virion assembly (vlf-1, HzNVorf140–1, and HzNVorf140–2), and viral infectivity (pif-0 and vp91). Although the functions of most nudivirus-like genes are generally conserved among baculoviruses, nudiviruses, and bracoviruses, lef-5, K425_459, 11k, and vp91 appear to have undergone functional divergence relative to their homologs in baculoviruses, nudiviruses, and Microplitis demolitor bracovirus, highlighting lineage-specific adaptations in CvBV. Collectively, our work provides a molecular framework for understanding CvBV assembly and serves as a valuable resource for investigating bracovirus evolution.