In silico identification of neuropeptide genes encoded by the genome of Crassostrea virginica with a special emphasis on feeding-related genes.

Abstract

Suspension-feeding bivalves, including the oyster Crassostrea virginica, use mucosal lectins to capture food particles. For instance, oysters can increase the transcription of these molecules to enhance food uptake. However, the regulatory processes influencing food uptake remain unclear although likely involve neuropeptides. Information on the neuropeptidome of C. virginica is limited, hindering the comprehension of its physiology, including energy homeostasis. This study explored the genome of C. virginica to identify neuropeptide precursors in silico and compared these with orthologs from other mollusks. A special focus was given to genes with potential implication in feeding processes. qPCR was used to determine the main organs of transcription of feeding-related genes. To further probe the function of target neuropeptides, visceral ganglia extracts and synthetic NPF were injected into oysters to evaluate their impact on genes associated with feeding and energy homeostasis. A total of eighty-five neuropeptides genes were identified in C. virginica genome. About 50 % of these are suggested to play a role in feeding processes. qPCR analyses showed that visceral ganglia and digestive system are the main organs for the synthesis of feeding-related neuropeptides. Further, results showed that the transcription of several neuropeptide genes in the visceral ganglia, including NPF and insulin-like peptide, increased after starvation. Finally, the injection of visceral ganglia extracts and synthetic NPF increased the transcription of a mucosal lectin and a glycogen synthase, known to be involved in food capture and glucose storage. Overall, this study identifies key genes regulating oyster physiology, enhancing the understanding of the control of basic physiological mechanisms in C. virginica.