A model for rhythmic and temperature-independent growth in ‘clock’ mutants of neurospora

Abstract

The Q 10 for the frequency (number of bands per 24 hours) of the ‘clock’ mutant (strain CL11A) of Neurospora crassa over the range 20–30° C is close to 1.0. By contrast, that for the double mutant, ‘wrist watch’ (strain CL12a), is closer to 2 over this temperature range. Strain CL12a differs from ‘clock’ in other ways as well, including 1) decreased rate of linear extension and band size, 2) greater sensitivity of growth rate to high temperatures and, 3) masking of rhythmic growth below 15° C. The response to temperature of several colonial mutants and standard (‘wild-type’) strains was studied and it is shown that some strains are temperature-independent yet arhythmic. A temperature-compensation model is presented to explain the response of ‘clock’ mutants to temperature and it is concluded that they demonstrate a non-circadian free-running endogenous rhythm.