Entrainment elicits period aftereffects in neurospora crassa

摘要

Circadian clocks continue to oscillate in constant conditions with their own period (τ) 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 τ of their initial free-run often depends on the nature of the prior zeitgeber. These postentrainment effects on period (τ-aftereffects) have predominantly been reported for animals but, so far, not fungi. The authors therefore investigated τ 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 (222h) and to zeitgebers with six different T (1626h), and then released to constant darkness. τ-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 τ-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 τ-aftereffects are based on interactions of oscillators within a cellular network. The present findings in Neurospora, which grows as a syncytium, suggest that τ-aftereffects also exist in circadian systems based on multioscillatory networks organized at the molecular level.