title: Enhancer of zeste plays an important role in photoperiodic modulation of locomotor rhythm in the cricket, Gryllus bimaculatus.
abstract: BACKGROUND
  Insects 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.
  
  
  RESULTS
  To 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.
  
  
  CONCLUSIONS
  These results suggest that histone modification by Gb'E(z) is involved in photoperiodic modulation of the G. bimaculatus circadian rhythm.
authors.affiliation: Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530 Japan.
authors.forename: Yoshimasa
authors.initials: Y
authors.lastname: Hamada
authors.affiliation: Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530 Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Tokuoka
authors.affiliation: Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Kita-ku, Okayama 700-8558 Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Bando
authors.affiliation: Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Kita-ku, Okayama 700-8558 Japan.
authors.forename: Hideyo
authors.initials: H
authors.lastname: Ohuchi
authors.affiliation: Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530 Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Tomioka
keywords: Circadian rhythm; Clock gene; Enhancer of zeste; Histone modification; Photoperiodic modulation