Enhancer of zeste plays an important role in photoperiodic modulation of locomotor rhythm in the cricket, Gryllus bimaculatus

Abstract

IntroductionInsects show daily behavioral rhythms controlled by an endogenous oscillator, the circadian clock. The rhythm synchronizes to daily light–dark cycles (LD) and changes waveform in association with seasonal change in photoperiod.ResultsTo explore the molecular basis of the photoperiod-dependent changes in circadian locomotor rhythm, we investigated the role of a chromatin modifier, Enhancer of zeste (Gb’E(z)), in the cricket, Gryllus bimaculatus. Under a 12 h:12 h LD (LD 12:12), Gb’E(z) was constitutively expressed in the optic lobe, the site of the biological clock; active phase (α) and rest phase (ρ) were approximately 12 h in duration, and α/ρ ratio was approximately 1.0. When transferred to LD 20:4, the α/ρ ratio decreased significantly, and the Gb’E(z) expression level was significantly reduced at 6 h and 10 h after light-on, as was reflected in the reduced level of trimethylation of histone H3 lysine 27. This change was associated with change in clock gene expression profiles. The photoperiod-dependent changes in α/ρ ratio and clock gene expression profiles were prevented by knocking down Gb’E(z) by RNAi.ConclusionsThese results suggest that histone modification by Gb’E(z) is involved in photoperiodic modulation of the G. bimaculatus circadian rhythm.

Photoperiod and temperature separately regulate nymphal development through JH and insulin/TOR signaling pathways in an insect

“…One possible mechanism is through epigenetic control, such as chromatin or DNA modification. In fact, trimethylation of histone H3K27 is involved in photoperiodic modulation of the circadian rhythms in the cricket, Gryllus bimaculatus (39). In G. bimaculatus, photoperiods modulate the circadian waveform of the locomotor rhythm and the optic lobe electrical activity in an experience-dependent manner, and the modulated waveform continues for a long period (40,41).…”