Roles of transient receptor potential channels in eclosion and movement in the red flour beetle Tribolium castaneum

Transient receptor potential channels (TRPs) are a family of cation channels involved in various sensory mechanisms in Drosophila melanogaster, including mechanosensing. Phylogenetic analysis of mechanosensory TRPs in seven members of the TRPV, TRPN and TRPA subfamilies reveals a unique TcTrpA5 in Tribolium castaneum that is likely lost in D. melanogaster. Because mechanosensors are implicated in various key physiology, we investigate the roles of eight candidate mechanosensory TRPs in survival, walking behaviour and tonic immobility in T. castaneum using the RNA interference technique. Double-stranded RNA treatment of nompC (dsNompC) and trpA5 (dsTrpA5) results in eclosion failure, causing 93% mortality of beetles subjected to each of these treatments. The beetles that survive the dsNompC treatment show defects during sclerotization of the elytra. Adult beetles treated with dsNanchung and dsInactive show defects in the folding of the joint between the femur and tibia segments of the hind legs, resulting in abnormal walking behaviour and reduced walking speed. Regarding tonic immobility induced by mechanical stimulations on the ventral surface, knockout responses (death feignings) are significantly extended with dsNanchung, dsInactive and dsWaterwitch treatments. These data suggest that both nompC and trpA5 are required for adult eclosion. The functions of nanchung and inactive are involved in the folding the hind leg segments. In addition, nanchung, inactive, and waterwitch are likely the receptors involved in recovery from tonic immobility.