Certain strains of the braconid parasitoid Cotesia melanoscela carry two different viruses within their ovaries, one of which (here designated CmV2) is apparently not a polydnavirus. Virus replication occurs in the ovarian calyx and in some other tissues of both male and female parasitoids; as yet, no replication has been observed in the testis, however. In addition, CmV2 is one of only two parasitoid viruses known to replicate in host insect larvae, and we not show that this virus is also capable of replicating in vitro; the virus is nevertheless nonpathogenic for gypsy moth larvae. The virus is not transmissible per os, either to host animals or to larvae of parasitoid strains lacking it. CmV2 is stably maintained within strains carrying it apparently by a vertical transmission mode involving the maternal line; transmission via the male germ line could not be demonstrated. While purification of the virus was not achieved, preliminary work allows us to suggest the genome consists of a single double-stranded DNA molecule of approximately 125 kb.
Summary Earlier studies have suggested that successful parasitism by certain braconid parasitoids may depend on the presence in host insect larvae of both polydnavirus and venom. We have shown that venom from the braconid parasitoid, Cotesia melanoscela, was required for in vivo persistence of polydnavirus DNA in host larvae. In parallel studies using an in vitro system, we observed that in the presence of venom nucleocapsids were released into the cytoplasm and subsequently uncoated at nuclear pores; in the absence of venom, this sequence of events was not observed.
Rabbit aortic tissue was labeled with 3H-phenoxybenzamine or 14C-dibenamine and treated with collagenase and elastase to remove collagen and elastin. The residue consisting of numerous small membranous vesicles and disrupted aggregates of actomyosin was treated with 2% SDS-EtSH and chromatographed on a Sephadex G-200 column. The radioactivity was located in a protein peak of molecular weight approximately 64,000 thus providing a demonstration of a protein-2-halogenoethylamine complex in smooth muscle.
