Identification of candidate mechanosensory transduction channels in the aquatic insect Protohermes xanthodes (Megaloptera: Corydalidae) by transcriptome analysis.

Protohermes species are among the top aquatic predators in benthic invertebrate communities. Their ability to perceive mechanical stimuli may be functional in mediating responses to freshwater environmental cues. In this study, we performed a transcriptome analysis of the antennae, maxillae, and labium of Protohermes xanthodes Navás larvae (Megaloptera: Corydalidae), identifying 2 transmembrane protein genes (PxanPiezo and PxanNompC), which are phylogenetically related to mechanosensory transduction channels in other insects. PxanPiezo is a large transmembrane protein featuring 38 transmembrane helices that mediate its association with the cytoplasm. PxanNompC is another transmembrane protein containing an extensive intracellular ankyrin repeat domain, a structural feature that enables potential interactions with the cytoskeleton. PxanPiezo is widely expressed in the internal tissues, such as nerve tissue, the digestive organs, the excretory organ, and the energy storage tissue, as well as in the body surface tissues, including the antennae, maxillae, labium, legs, lateral filaments, anal prolegs, and the abdominal integument. In contrast, PxanNompC exhibits tissue-specific expression in body surface structures and is highly expressed in the abdominal integument. These results suggest that PxanPiezo and PxanNompC possess the structural basis required to convert mechanical stimuli into signal currents. Their distinct structural features and expression profiles imply potential differences in their mechanoelectrical transduction mechanisms. Furthermore, identifying mechanoelectrical transduction channel genes in P. xanthodes could facilitate the studies on the sensory mechanisms of this aquatic insect adapting the freshwater environments.