Novel biopesticides targeting the neuromuscular system of the peach potato aphid Myzus persicae

Abstract

The amount of biopesticides currently used in pest control is still below 1% of the global pesticide market, with environmentally damaging products constituting the majority of all commercial insecticides. There is thus an increased need for biopesticides, including those from invertebrate venoms, which are often highly specific. One example of this is to use a fusion protein approach where a peptide-toxin is fused to a carrier protein, in this instance GNA, which has the capability of crossing the insect gut epithelium allowing inhibitory molecules of the neuromuscular system to be delivered to these remote sites of action via oral ingestion. In this study, five variants of spider Segestria florentina toxin (SFI) fused to snowdrop lectin (Galanthus nivalis agglutinin; GNA) were successfully expressed in Pichia pastoris X33 and subsequently purified. To improve the level of expression of the intact recombinant protein SFI1/GNA, an expression vector construct containing two gene copies was assembled. Insecticidal activities of all these novel fusion proteins were demonstrated by oral feeding to Myzus persicae. SFI1, SFI3, SFI5, SFI6, and SFI8 GNA-based fusion proteins (0.1 mg/ml), which target voltage-gated ion channels in the insect CNS, caused significant mortality to M. persicae compared to GNA alone. LC50 values for the variants 2XSFI1/GNA, SFI5/GNA and SFI8/GNA were 0.006 mg/ml, 0.038 mg/ml, and 0.08 mg/ml respectively. The GNA-based fusion proteins expressing -conotoxin E1 from cone snails, which target nicotinic acetylcholine receptors, was also successfully expressed in P. pastoris; in these, GNA was at the N-terminus and the toxin at the C-terminus. The LC 50 values for the GNA/-conotoxin E1 was 8 μg/μl. The results demonstrate that these candidate molecules show promise for future development as bio-pesticides.