Effects of Simultaneous Expression of Two Sodium Channel Toxin Genes on the Properties of Baculoviruses as Biopesticides

Abstract

Abstract Previously, we have described the properties of recombinant baculoviruses expressing three chimeric genes, mag4, sat2, and ssh1, that encode secretable insect selective sodium channel toxins, μ-Aga-IV from the spider Agelenopsis aperta, As II from the sea anemone Anemonia sulcata, and Sh I from the sea anemone Stichadactyla helianthus, respectively. We now show that μ-Aga-IV and As II act at distinct sites on voltage-sensitive sodium channels of insects and synergistically promote channel opening. We also show that these toxins have synergistic insecticidal activity against the blowfly Lucilia sericata and the fall armyworm Spodoptera frugiperda. To determine if toxin synergy also occurs in the context of virus replication, we inserted the chimeric toxin genes into nonessential sites of the Autographa californica nuclear polyhedrosis virus (AcMNPV) genome under the control of either a modified promoter, P synXIV , or an insect derived promoter, P hsp70 . Comparative analyses showed that viruses expressing toxin genes under the control of the P hsp70 promoter were more effective as biopesticides than under the control of P synXIV . Two toxins, μ-Aga-IV and As II, exerted the most potent effects in S. frugiperda and Trichoplusia ni larvae, respectively. A virus simultaneously expressing two P hsp70 -promoted toxin genes, mag4 and sat2, exhibited properties similar to the two viruses expressing each of the toxin genes individually except that larval feeding time (FT 50 ) was reduced an additional 10%, indicating a small advantage to coproducing synergistic toxins.