Regulation of opsin and circadian clock genes on mate-finding behavior of the day-flying red moth, Phauda flammans (Walker).

First, significantly higher mate-finding success was found under light condition than under constant darkness condition in Phauda flammans , a typical diurnal moth. We speculate that mate-finding behavior in P. flammans may be influenced by the light-sensitive opsin genes Long wavelength opsin ( PfLW ), Ultraviolet opsin ( PfUV ) and Blue opsin ( PfBL ), which are potentially regulated by both light-cues and endogenous circadian rhythms. Second, the circadian clock genes Period ( PfPer ), Timeless ( PfTim ), Cryptochrome1 ( PfCry1 ), Cryptochrome2 ( PfCRY2 ), Cryptochrome3 ( PfCry-like ), Clock ( PfClk ), Cycle ( PfCyc ), Vrille ( PfVri ), and Slimb ( PfSli ) were identified in P. flammans . Third, circadian rhythms in the relative expression levels of opsin and circadian clock genes were demonstrated via quantitative real-time PCR analysis, with peak expression coinciding with the mate-finding peak. Notably, the relative expression of PfLW in males P. flammans was significantly higher than that in females P. flammans at the mate-finding peaks Zeitgeber time (ZT) 8 and ZT 10 under light, while the expression of the opsin gene PfBL showed a similar pattern at ZT 10 under light. Additionally, the expression of the clock gene PfCry-like was significantly higher in males than in females at ZT 8 and ZT 10 under light, while PfPer , PfTim , PfClk and PfCyc exhibited similar male-biased expression patterns at ZT 10 under light. Conversely, PfCry1 and PfVri expression was significantly higher in females than in male at ZT 8 under light. In conclusion, sex differences were detected in the expression of opsin and circadian clock genes, which indicated that light-mediated regulation of these genes may contribute to the daytime mate-finding behavior of P. flammans .