Genetic interactions between clock mutations in Neurospora crassa: can they help us to understand complexity?

Recent work on circadian clocks in Neurospora has primarily focused on the frequency (frq) and white-collar (wc) loci. However, a number of other gene s are known that affect either the period or temperature compensation of th e rhythm. These include the period (no relationship to the period gene of D rosophila) genes and a number of genes that affect cellular metabolism. How these other loci fit into the circadian system is not known, and metabolic effects on the clock are typically not considered in single-oscillator mod els. Recent evidence has pointed to multiple oscillators in Neurospora, at least one of which is predicted to incorporate metabolic processes. Here, t he Neurospora clock-affecting mutations will be reviewed and their genetic interactions discussed in the context of a more complex clock model involvi ng two coupled oscillators: a FRQ/WC-based oscillator and a 'frq-less' osci llator that may involve metabolic components.