CIRCADIAN-RHYTHMS IN FUNGI

Endogenous circadian clocks, present in both prokaryotes and eukaryote s, provide the machinery by which organisms keep in synchrony with the external world. The ability of the clock to measure accurate time all ows changes in the environment (particularly light and temperature) to be anticipated so that biological activities can occur at the appropr iate times of day. The observed circadian rhythms are, as a general fe ature, established through the daily control of specific target genes by the clock. Demonstrations of circadian rhythms are widespread, and in the fungi the clock has been shown to control daily rhythms in spor e development and liberation. Within the fungi, Neurospora crassa prov ides the preeminent model system for investigations into the underlyin g processes of circadian rhythms. Through genetic and molecular approa ches, significant progress has been made in describing the N. crassa c ircadian system. As discussed in this review, the analysis of the N. c rassa clock has provided important details on (i) how the clock is ass embled and (ii) how environmental signals are perceived by the clock, and (iii) a description of rhythmic output genes that are regulated by the clock.