Monarch butterflyCryptochrome 1loss-of-function mutants reveal differences in light entrainment of 24-hour behavioral rhythms in insects

Abstract

SUMMARYLight is one of the strongest cues for entrainment of circadian clocks in most organisms. Previous work inDrosophila melanogaster(dm) has shown that entrainment relies on both the visual system and the circadian, blue-light photoreceptor Cryptochrome (dmCRY). Here, we used the monarch butterflyDanaus plexippus(dp) to test conservation of this mechanism among insects and the relative importance of monarchCryptochrome 1(dpCry1) in the entrainment of its clockin vivo. We showed that loss of functionaldpCry1abolishes adult circadian eclosion behavior and molecular circadian rhythms in the monarch brain. These rhythms can be restored by entrainment to temperature cycles, demonstrating that the core circadian clock is intact indpCry1mutants. Importantly, we showed that rhythmic flight activity is also disrupted indpCry1mutants but not in the visually impaireddpNinaB1mutants, suggesting that unlikeDrosophilalight-entrainment of the monarch circadian clock relies solely on dpCRY1 photoreception.