New environmentally-friendly technologies for slug control based on orally-delivered fusion proteins containing specific molluscicidal toxins

Abstract

The aim of this project was to investigate the potential for a novel technology, originally conceived and developed for the control of insect pests, to be extended for the control of mollusc crop pests, with focus on the grey field slug Deroceras reticulatum.

This technology allows naturally occurring proteins, which have low, or no, toxicity when delivered orally to be converted into effective and orally active pesticides. The approach, patented by the academic partners, uses genes encoding fusion proteins that contain a plant-derived protein carrier (Galanthus nivalis agglutinin; GNA) linked to an insect derived peptide (neurohormone, venom toxin, etc.) that must normally be delivered to the blood in order to be active (e.g. via a sting). Whereas neither component of the fusion is toxic when fed alone or as a mixture, the fusion protein shows oral toxicity as a result of the carrier transporting the active peptide across the insect gut and delivering it to the blood, from where it can access the central nervous system. The proteins are produced in bacterial or yeast expression systems and delivered orally as a component of diet. Our primary aim was to investigate if peptides derived from the venom of mollusc-hunting cone snails (Conus spp.), that had previously been reported to have mollusc-specific activity (conotoxin), could be exploited for the generation of molluscicidal fusion proteins.

Considerable difficulties were encountered with the expression of functional cone snail-derived peptides. Nevertheless, we reported the first successful production of a conopeptide using a yeast-based system. Contrary to published claims, this conopeptide was found to have insecticidal activity and exhibited no toxicity towards slugs. The limited research that has been conducted with molluscs significantly restricted the number of candidates available for exploitation using fusion protein technology. Results obtained from this project have provided promising evidence to suggest that further investment in a biotechnological approach for the development of new molluscicides is worthwhile. An overview of the approach and results are presented in this report but disclosure is limited to protect Intellectual Property.