Originally published as Genetics Published Articles Ahead of Print on January 21, 2007.

Genetics, Vol. 175, 1175-1183, March 2007, Copyright © 2007
doi:10.1534/genetics.106.068270

Circadian Rhythms in Neurospora crassa: Clock Mutant Effects in the Absence of a frq-Based Oscillator

Laura Lombardi, Kevin Schneider, Michelle Tsukamoto and Stuart Brody¹

Division of Biological Sciences, University of California, San Diego, California 92093-0116

¹ Corresponding author: Division of Biological Sciences, University of California, San Diego, Mail Code 0116, 9500 Gilman Dr., La Jolla, CA 92093.
E-mail: sbrody{at}ucsd.edu

In Neurospora, the circadian rhythm is expressed as rhythmic conidiation driven by a feedback loop involving the protein products of frq (frequency), wc-1 (white collar-1), and wc-2, known as the frq/wc (FWC) oscillator. Although strains carrying null mutations such as frq¹⁰ or wc-2 lack a functional FWC oscillator and do not show a rhythm under most conditions, a rhythm can be observed in them by the addition of geraniol or farnesol to the media. Employing this altered media as an assay, the effect of other clock mutations in a frq¹⁰- or wc-2-null background can be measured. It was found that the existing clock mutations fall into three classes: (1) those, such as prd-3 or prd-4 or frq¹, that showed no effect in a clock null background; (2) those, such as prd-1 or prd-2 or prd-6, that did have a measurable effect in the frq¹⁰ background; and (3) those, such as the new mutation ult, that suppressed the frq¹⁰ or wc-2 effect, i.e., geraniol/farnesol was not required for a visible rhythm. This classification suggests that some of the known clock mutations are part of a broader multioscillator system.

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