Photoperiod alters the diurnal rhythm pattern of testicular transcription and metabolism in Brandt's voles.

Photoperiod changes serve as critical environmental signals for seasonally reproducing animals, with their decoding dependent on the precise functioning of endogenous circadian clocks. Here we conducted a comprehensive analysis of diurnal transcripts and metabolites profiles in the testes of Brandt's voles (Lasiopodomys brandtii) under long photoperiod (LP) and short photoperiod (SP), to elucidate the role of circadian rhythms within peripheral testicular tissue in regulating reproduction. Phenotypic results demonstrated that LP promoted testicular development, whereas SP suppressed it. Then we observed relatively weaker transcriptional and metabolic rhythmicity in the testes under both photoperiods. The function of diurnal rhythmic genes was mainly related to homeostasis, developmental, reproductive behavior, motility and sperm flagellum assembly pathways, suggesting that diurnal clocks act as photoperiodic timekeeper for reproductive timing. In contrast, testosterone biosynthesis and key energy metabolism pathways essential for spermatogenesis were largely governed by non-rhythmic genes expression patterns. Together, these findings underscore the non-uniform pervasiveness of diurnal rhythmicity in testis, where reproductive initiation driven by the diurnal clock, while subsequent spermatogenic processes progressively deviate from 24 h rhythmicity.