Colonies of the social wasp Polistes metricus were fed uninfected Spodoptera frugiperda larvae or larvae infected with either of two toxin-expressing recombinant baculoviruses or a recombinant virus containing the reporter gene, chloramphenicol acetyltransferase (cat). One of the toxin-expressing viruses contained a gene, tox34, encoding an insect-selective mite neurotoxin, TxP-I. The other contained AaIT, a gene encoding an insect-selective scorpion neurotoxin. Viruses used during the first half of the study contained the heterologous genes under the control of the Drosophila melanogaster HSP70 promoter, which is active constitutively in cells both permissive and nonpermissive to baculovirus infection. Viruses used during the latter half of the study contained the heterologous genes under very late viral promoter control. No difference between the wasp colonies fed uninfected S. frugiperda larvae and the colonies fed larvae infected with the toxin-expressing viruses was observed for the five developmental parameters tested. The presence of CAT and TxP-I, the toxin encoded by tox34 was detected in wasps fed the viruses with cat and tox34 under HSP70 promoter control, but no CAT activity was detected in wasps from colonies fed virus with cat under very late viral promoter control. TxP-I-related proteins were detected in one group of wasps fed larvae infected with the virus containing tox34 under very late viral promoter control. Promoter choice in constructing toxin-expressing recombinant baculoviruses for biological pest control is discussed.
