Fbxl4 Regulates the Photic Entrainment of Circadian Locomotor Rhythms in the Cricket Gryllus bimaculatus .

Photic entrainment is an essential property of the circadian clock that sets the appropriate timing of daily behavioral and physiological events. However, the molecular mechanisms underlying the entrainment remain largely unknown. In the cricket the immediate early gene plays an important role in photic entrainment, followed by a mechanism involving s (s). However, the association between expression and s remains unclear. In the present study, using RNA-sequencing analysis, we found that five family genes (, and ) encoding F-box and leucine-rich repeat proteins are likely involved in the mechanism following light-dependent induction. RNA interference (RNAi) of / significantly downregulated s expression, whereas RNAi of the genes exerted no effect on expression. The genes showed rhythmic expression under light-dark cycles (LDs) with higher expression levels in early day (), whole day (), or day-to-early night (, , and ), whereas their expression was reduced in the dark. We then examined the effect of their RNAi on the photic entrainment of the locomotor rhythm and found that RNAi of either disrupted or significantly delayed the re-entrainment of the locomotor rhythm to shifted LDs. These results suggest that light-induced expression stimulates expression to reset the circadian clock.