Engineering Insect-Resistant Plants by Transgenic Expression of an Insecticidal Spider-Venom Peptide

The insecticidal spider-venom peptide ω-hexatoxin-Hv1a (Hv1a) from the Australian Blue Mountains funnel-web spider Hadronyche versuta is one of the most potent insect-specific neurotoxins isolated to date. Hv1a blocks voltage-gated calcium channels in the insect central nervous system, a mechanism quite distinct from existing chemical insecticides. It induces a slow-onset paralysis that precedes death in a taxonomically wide range of insects. Hv1a's broad spectrum of target insects, novel mode of action, and absence of toxicity to vertebrates makes the Hv1a gene an attractive tool for generating insect-resistant transgenic crops. The oral activity of Hv1a can be enhanced by coupling it to the plant lectin Galanthus nivalis agglutinin (GNA) or with the minor capsid protein of pea enation mosaic virus (CP). Recombinant fusions of Hv1a with GNA were produced using the Pichia pastoris expression system to study the intrinsic insecticidal activity of Hv1a-GNA and GNA-Hv1a fusion proteins. By using injection bioassays with houseflies, we found that the intrinsic insecticidal activity of Hv1a was maintained when it was fused to GNA. Moreover, feedin