Females of the parasitic wasp Diachasmimorpha longicaudata (DL) introduce an entomopoxvirus (EPV) with their eggs into larvae (hosts) of the Caribbean fruit fly, Anastrepha suspensa and other fruit flies (Diptera: Tephritidae). This virus (DLEPV) enhances the survival of the wasp's egg by disrupting the encapsulation response of host's hemocytes. DLEPV has a biconcave central core with two lateral bodies, a cytoplasmic site of replication, and a unipartite DNA genome of 250-300kb that is highly A-T rich. Studies to further test the hypothesis that DLEPV is a Group C (Diptera-infecting) EPV were designed to (1) identify possible occlusion bodies (a characteristic of EPVs) in the wasp and host, using transmission electron microscopy (TEM), (2) identify characteristic poxvirus motifs in DLEPV nucleotide and derived protein sequences, and (3) estimate the phylogenetic position of DLEPV relative to other EPVs and vertebrate poxviruses. TEM revealed that DLEPV-associated electron-dense plaques occur within an extracellular matrix (lumen) of the poison gland of female wasps. However, no occlusion bodies were present in the wasp or in host hemocytes. Blastp, ClustalW, ClustalX, and Prosite analyses identified DLEPV ORFs that encode putative NPH1, polyA polymerase, and NTPase proteins that have 32-68% amino acid identity with other poxvirus homologs. PAUP phylogenetic analysis of five additional putative protein sequences including the rifampicin resistance (RIF) protein, demonstrated that DLEPV is related to but distinct from AMEPV and HAEPV (Lepidoptera-infecting) and from MSEPV (Orthoptera-infecting) Group B EPVs and is the first Diptera-infecting EPV whose genes have been sequenced.
Supported by National Science Foundation grant IBN9986076.
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