Clock genes influence mate‐searching behaviour and opsin gene expression in a diurnal moth

Abstract Lepidoptera comprise butterflies and moths, which generally exhibit distinct diurnal and nocturnal activity rhythms, respectively. While clock genes are well known to play a critical role in regulating reproductive behaviour in nocturnal moths, their putative functions in diurnal moths remain largely unclear. Here, we used the day‐flying moth, Phauda flammans (Walker), as a model to investigate the developmental stage‐ and tissue‐specific expression patterns of homologous clock genes, and to elucidate the potential roles of key clock genes in mate‐searching—an essential component of reproductive success. Our results showed that nine homologous clock genes, such as period ( Pfper ), timeless ( Pftim ), cryptochrome1 ( Pfcry1 ), cryptochrome2 ( Pfcry2 ), cryptochrome‐like ( Pfcry‐like ), Clock ( PfClk ), cycle ( Pfcyc ), vrille ( Pfvri ) and slimb ( Pfsli ), were expressed across eggs, larvae, pupae and adults of P. flammans . Among different tissues of adults, these clock genes were predominantly highly expressed in the antennae. RNA interference‐mediated knockdown of Pfcry1 , Pfcry‐like and Pfvri led to a significant alteration in the expression of all opsin genes ( long‐wavelength , ultraviolet and blue ) and a reduction in mate‐searching success in P. flammans , indicating that these clock genes are involved in regulating mate‐searching through the regulation of opsin genes. These findings provide new insights into the molecular mechanisms by which clock genes regulate reproductive behaviour in diurnal moths.