Abstract: Cryptochromes (CRYs) are photolyase-like blue-light receptors originally identified in Arabidopsis thaliana (Arabidopsis) and have since been identified across diverse evolutionary lineages. Cryptochromes not only transduce blue-light cues to the circadian clock but also maintain the temperature compensation of circadian clock. However, the precise mechanism by which CRYs integrate blue light signals into the circadian clock in Arabidopsis is still under investigation. This study revealed that, when blue light was filtered out from white light, the circadian period length in Col-0 was extended, but not in the cry1 cry2 double mutant. This indicates that both blue light and CRYs are crucial for regulating the circadian rhythm. Furthermore, we discovered that CRY2 interacted with PSEUDORESPONSE REGULATOR 5 (PRR5), a key component of the circadian clock under blue light, which suppressed PRR5's transcriptional inhibition ability on CCA1 and LHY. These findings illuminate the pathway through which blue light influences the circadian clock via the CRY2–PRR5 module.

Key words: blue light, CCA1, circadian clock, CRY2, LHY, PRR5