Circadian rhythms in Neurospora crassa: a mutation affecting temperature compensation

Area of Science:

• Mycology
• Chronobiology
• Molecular Genetics

Background:

• Circadian rhythms in Neurospora crassa exhibit temperature compensation, meaning their period is largely unaffected by temperature changes.
• The Q10 value quantifies the rate change with a 10°C temperature increase; a Q10 near 1 indicates compensation, while higher values suggest temperature dependence.

Purpose of the Study:

• To investigate the role of the cel locus mutation in disrupting temperature compensation of the circadian rhythm in Neurospora crassa.
• To determine the effect of fatty acid supplementation on the temperature compensation threshold in cel mutant strains.

Main Methods:

• Measuring the Q10 of the circadian rhythm of conidiation in wild-type and cel mutant Neurospora crassa strains across a temperature range (14-30°C).
• Supplementing cel mutant strains with various fatty acids (unsaturated, short-chain, long-chain saturated) and assessing their impact on the rhythm's Q10 and period.
• Identifying the threshold temperature (break point) at which temperature compensation is lost or gained in cel mutants.

Main Results:

• The wild-type bd csp strain showed a low Q10 (1.1) for its circadian rhythm, indicating temperature compensation, unlike its growth rate (Q10=2.4).
• The cel mutation abolished temperature compensation below 22°C (Q10=2.2, period ~40 hr) but retained it above 22°C (Q10=1.1, period 18-21 hr).
• Fatty acid supplementation modulated the threshold temperature: unsaturated/short-chain fatty acids raised it to 26°C, while long-chain saturated fatty acids lowered it to 18°C.

Conclusions:

• The cel locus is crucial for maintaining temperature compensation of the circadian rhythm in Neurospora crassa.
• Fatty acids, either as membrane components or metabolites, are implicated in the molecular mechanism underlying circadian rhythm temperature compensation.
• The study highlights a temperature-dependent regulatory role for fatty acids in biological timing.