title: Entrainment elicits period aftereffects in Neurospora crassa.
abstract: Circadian clocks continue to oscillate in constant conditions with their own period (tau) and entrain to a cyclic environment by adjusting their intrinsic period to that of the zeitgeber. When circadian clocks are released from entrained to constant conditions, the tau of their initial free-run often depends on the nature of the prior zeitgeber. These postentrainment effects on period (tau-aftereffects) have predominantly been reported for animals but, so far, not fungi. The authors therefore investigated tau aftereffects in the classic circadian model system Neurospora crassa. The standard laboratory strain frq+, the short-period mutant frq(1), and the long-period mutant frq(7) were entrained to 11 different photoperiods in a 24-h day (2-22 h) and to zeitgebers with six different T (16-26 h), and then released to constant darkness. tau-Aftereffects in response to different photoperiods correlated weakly with prior photoperiod in frq+ and were unsystematic in both period mutant strains. Strength and direction of the tau-aftereffect in zeitgeber cycles with different T depended on their length and on the strain, showing a negative correlation with zeitgeber length in frq+ and positive correlations in frq(1) and frq(7). It has been proposed that tau-aftereffects are based on interactions of oscillators within a cellular network. The present findings in Neurospora, which grows as a syncytium, suggest that tau-aftereffects also exist in circadian systems based on multioscillatory networks organized at the molecular level.
authors.affiliation: Institute for Medical Psychology, Ludwig-Maximilian University, Munich, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Diegmann
authors.forename: Astrid
authors.initials: A
authors.lastname: Stück
authors.forename: Cornelia
authors.initials: C
authors.lastname: Madeti
authors.forename: Till
authors.initials: T
authors.lastname: Roenneberg
mesh_terms: D057906:Circadian Clocks / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D003624:Darkness; D008027:Light; D009492:Neurospora crassa / Q000502:physiology; D017440:Photoperiod