INTERGENERIC COMPLEMENTATION OF A CIRCADIAN RHYTHMICITY DEFECT - PHYLOGENETIC CONSERVATION OF STRUCTURE AND FUNCTION OF THE CLOCK GENE-FREQUENCY

The Neurospora crassa frequency locus encodes a 989 amino acid protein that is a central component, a state variable, of the circadian biolo gical clock. We have determined the sequence of all or part of this pr otein and surrounding regulatory regions from additional fungi represe nting three genera and report that there is distinct, preferential con servation of the frequency open reading frame (ORF) as compared with n on-coding sequences. Within the coding region, many of the domain hall marks of the N.crassa protein are highly conserved, especially an inte rnal region bearing the causative mutations in frq(1) and frq(7), the most extreme alleles in the frequency allelic series. Despite consider able diversity among the strains analyzed in terms of morphology, grow th, circadian clock output and frq sequence, the ORF from the most dis tantly related fungus included in this study (Sordaria fimicola) rescu es rhythmicity in a N.crassa frequency null strain. Both sequence cons ervation, and the ability of frequency from a genus displaying one dev elopmental program to complement circadian defects in a separate genus with a distinct, clock-regulated developmental program, are consisten t with a central role of the frequency gene product in a general circa dian oscillator capable of controlling diverse outputs in a variety of systems.