Neuropeptide signalling systems present promising avenues for the development of new pest control agents due to their integral roles in insect homeostasis, development, and behaviour. This project primarily examines the crop of the foregut, a muscular organ presents in almost all but not exclusively in the order Diptera, serving the dual purposes of food storage and regurgitation.
Myosuppressin and its receptors, which are well-conserved across insect orders, are known to inhibit muscle contractions in the gut, positioning them as prime candidates for disrupting gut function. A critical aspect of this study is understanding that only when ingested food efficiently passes through the foregut can the animal continue its feeding process, highlighting a potential target area for intervention.
Using mass spectrometry and immunohistochemistry, we confirmed the identity and spatial distribution of this peptide in the foreguts of two economically significant agricultural pests; cabbage root fly, Delia radicum and medfly, also known as Mediterranean fruit fly, Ceratitis capitata. Our physiological findings highlight myosuppressin capability to significantly inhibit spontaneous crop contractions, responding even to nano- and pico-molar peptide concentrations. Leveraging the adaptable genetics of Drosophila melanogaster, we delved into the potential roles of two myosuppressin G-protein-coupled receptors, DmsR-1 and DmsR-2, in regulating crop muscle contractions. Employing knock-out mutants for both receptors, we established that DmsR-1 plays a critical role in the robust inhibition of crop contractions. Myosuppressin was observed to degrade swiftly when exposed to peptidases in crop of D. radicum. Consequently, we tested a biostable myosuppressin receptor agonist, Benzethonium chloride (Bztc), for its potential to disrupt crop function. Microinjections of the native peptide led to complete oviposition inhibition, highlighting a potential new pathway for myosuppressin signalling that warrants further exploration. This finding emphasizes the potential of myosuppressin as an eco-friendly pest control agent. Given the substantial economic implications associated with the medfly, our neuropeptidome analysis offers a rich repository of prospective novel targets.
The discussion further delves into the advantages and challenges of harnessing peptidergic signalling for insect control. It particularly addresses the inherent biostability issues of peptides and underscores the necessity for metabolically stable analogues that can engage with peptide receptors while minimizing degradation
