The period gene alters daily and seasonal timing in Ostrinia nubilalis

The timing of insects’ daily (feeding, movement) and seasonal (diapause, migration) rhythms affects their population dynamics and distribution. Yet, despite their implications for insect conservation and pest management, the genetic mechanisms underlying variation in timing are poorly understood. Prior research in the European corn borer moth ( Ostrinia nubilalis ) associated ecotype differences in seasonal diapause and daily activity with genetic variation at the circadian clock gene period ( per ). Here, we demonstrate that populations with divergent allele frequencies at per exhibit differences in daily behavior, seasonal development, and the expression of circadian clock genes. Specifically, later daily activity and shortened diapause were associated with a reduction and delay in the abundance of cycling per mRNA. CRISPR/Cas9-mediated mutagenesis revealed that per and/or an intact circadian clock network were essential for the appropriate timing of daily behavior and seasonal responsiveness. Furthermore, a reduction of per gene dosage in per heterozygous mutants ( per ^-/+ ) pleiotropically decreased the diapause incidence, shortened post-diapause development, and delayed the timing of daily behavior, in a manner phenotypically reminiscent of wild-type individuals. Altogether, this combination of observational and experimental research strongly suggests that per is a master regulator of biological rhythms and may contribute to the observed life cycle differences between bivoltine (two generation) and univoltine (one generation) O. nubilalis .