A ShK-like domain from Steinernema carpocapsae with bioinsecticidal potential

Entomopathogenic nematodes are used as biological control agents against a broad range of insect pests. We ascribed the pathogenicity of these organisms to the excretory/secretory products (ESP) released by the infective nematode. Our group characterized different virulence factors produced by Steinernema carpocapsae that underlie its success as an insect pathogen. A novel ShK-like peptide (ScK1) from this nematode that presents high sequence similarity with the ShK peptide from a sea anemone was successfully produced recombinantly in Escherichia coli . The secondary structure of ScK1 appeared redox-sensitive, exhibiting a far-UV circular dichroism spectrum consistent with an alpha-helical secondary structure. Thermal denaturation of the ScK1 allowed estimating the melting temperature to 59.2 ± 0.1 °C. The results from toxicity assays using Drosophila melanogaster as a model show that injection of this peptide can kill insects in a dose-dependent manner with an LD 50 of 16.9 µM per adult within 24 h. Oral administration of the fusion protein significantly reduced the locomotor activity of insects after 48 h ( p < 0.05, Tukey’s test). These data show that this nematode expresses insecticidal peptides with potential as next-generation insecticides. J.F. received a doctoral grant from the FCT (SFRH/BD/131698/2017). This work was funded by Fundo Europeu de Desenvolvimento Regional (FEDER) under project NanoNema (ACORES-01- 0145-FEDER000113), approved by the Autoridade de Gestão do Programa Operacional AÇORES 2020. J.B.V. acknowledges support by FCT-Fundação para a Ciência e a Tecnologia, Portuguese Institute (P.I), through iNOVA4Health (UIDB/04462/2020, UIDP/04462/2020) and LS4FUTURE Associated Laboratory (LA/P/0087/2020). G.B. and P.P. acknowledge funding from NORCE Norwegian Research Centre to host JF as well as funding from the Research Council of Norway (Grant ID: 221568) for expansion of the expression vector suite.