the frequency/white collar oscillator; they do not possess all of the characteristics of a circadian clock on their own because this is supplied by the fwo. however, rhythms in clock-controlled gene-16 (ccg-16) are coupled to the fwo but function autonomously, demonstrating that neurospora crassa contains at least 2 potential pacemakers, but only one that can be reset by light and temperature while maintaining temperature compensation. the frq-less oscillator has never been proven to affect the true circadian clock. the mechanism and significance for frq-less oscillators (flo) are still under research. evolution the frq protein is conserved within the sordariacea but diverges outside of this group. nonetheless bona fide frq-based circadian cocks have been found in organisms other than neurospora both within the sordariacea, for instance, in the salient fungal pathogen botrytis, and also as far afield as pyronema within the pezizomycetes, an early-diverging lineage of filamentous ascomycetes. frq was even found in non-dikarya group of fungi. the finding of frq and conserved circadian clock mechanism inside non-dikarya, arbuscular mycorrhizal fungi expanded the evolutionary history of this gene in fungal kingdom. frq seems to diverge very quickly during its evolution. a part of the reason why the frq primary amino acid sequence diverges so quickly may be because it is an intrinsically disordered protein and as a result lacks the structural constraints that limit sequence changes. since codon optimization of the frq gene results in impaired circadian feedback loop function, frq displays non-optimal codon usage bias across its open reading frame in contrast to most other genes. frq is an intrinsically disordered protein that is not well conserved, even across fungi. unlike frq, however, wc-1 is very well conserved. it is the founding member of the family of blue light photoreceptors used in the entire kingdom of fungi. moreover, it is similar in structure and function to bmal1. casein kinase 2 is conserved in the circadian oscillators of plants (arabidopsis) and flies (drosophila). a similar form of cki is necessary for the degradation of period (per) proteins in drosophila and mammals. the drosophila gene slimb is orthologous to fwd1 in neurospora, both of which are crucial for clock protein degradation. in general, the ttfls found in fungi and animals share a similar regulatory architecture, with a single step negative feedback loop, pas-pas heterodimeric activators that are conserved, and negative element proteins that largely lack structure and are much less well conserved. a similar palette of kinases modifies the clock proteins in all cases.