Signal Sequence and Promoter Effects on the Efficacy of Toxin-Expressing Baculoviruses as Biopesticides

Baculovirus recombinants expressing a neurotoxin gene,tox34,from the straw itch mitePyemotes triticihave been previously shown to paralyze or kill insects approximately 50% faster than wild-type. We constructed a series of recombinants of the baculovirusAutographa californicanucleopolyhedrovirus which expressedtox34with different signal sequences or were controlled by different promoters to evaluate their influence on toxin expression in cell culture and in insects. Heterologous signal sequences provided no significant increase in the overall levels of the maturetox34gene product, Tox34, secreted into the tissue culture media from infected cells and no improvement in the time required for paralysis of insect hosts. The time required for paralysis was promoter-dependent; the late 6.9K DNA binding protein gene promoter was generally the most effective promoter, although an insect HSP70 promoter was equally or more effective in one of the species.