| Abstrakt: |
Previously, we have described the properties of recombinant baculoviruses expressing three chimeric genes,mag4, sat2,andssh1,that encode secretable insect selective sodium channel toxins, μ-Aga-IV from the spiderAgelenopsis aperta,As II from the sea anemoneAnemonia sulcata,and Sh I from the sea anemoneStichadactyla 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 blowflyLucilia sericataand the fall armywormSpodoptera frugiperda.To determine if toxin synergy also occurs in the context of virus replication, we inserted the chimeric toxin genes into nonessential sites of theAutographa californicanuclear polyhedrosis virus (AcMNPV) genome under the control of either a modified promoter, PsynXIV, or an insect derived promoter, Phsp70. Comparative analyses showed that viruses expressing toxin genes under the control of the Phsp70promoter were more effective as biopesticides than under the control of PsynXIV. Two toxins, μ-Aga-IV and As II, exerted the most potent effects inS. frugiperdaandTrichoplusia nilarvae, respectively. A virus simultaneously expressing two Phsp70-promoted toxin genes,mag4andsat2,exhibited properties similar to the two viruses expressing each of the toxin genes individually except that larval feeding time (FT50) was reduced an additional 10%, indicating a small advantage to coproducing synergistic toxins. |
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