Possible link between circadian rhythm and heat shock response in Neurospora crassa.

3-h pulses of elevated temperatures (30 degrees C, 35 degrees C, 40 degrees C) phase shift the circadian conidiation rhythm of Neurospora crassa. The phase and amplitude of the phase response curves (PRC) were measured in wild type (frq+) and frequency mutants (frq 1, frq 7). The dose dependence of the phase shifts was compared to the dose dependence of total protein synthesis inhibition and heat shock protein induction in the three strains. All processes showed an almost linear dependence on temperature. These experiments and other available data suggest that a temperature increase may act on the circadian rhythm by a process belonging to the heat shock response.