Epistatic and synergistic interactions between circadian clock mutations in Neurospora crassa

We identified a series of epistatic and synergistic interactions among the circadian clock mutations of Neurospora crassa that indicate possible physi cal interactions among the various clock components encoded by these genes. The period-6 (prd-6) mutation, a short-period temperature-sensitive clock mutation, is epistatic to both the prd-2 and prd-3 mutations. The prd-2 and prd-3 long-period mutations show a synergistic interaction in that the per iod length of the double mutant strain is considerably longer than predicte d. In addition, the prd-2 prd-3 double mutant strain also exhibits overcomp ensation to changes in ambient temperature, suggesting a role in the temper ature compensation machinery of the clock. The prd-2, prd-3, and prd-6 muta tions also show significant interactions with the frq(7) long-period mutati on. These results suggest that the gene products of prd-2, prd-3, and prd-6 play an important role in both the timing and temperature compensation mec hanisms of the circadian clock and may interact with the FRQ protein.