Molecular and Behavioral Analysis of Four period Mutants in Drosophila melanogaster Encompassing Extreme Short, Novel Long, and Unorthodox Arrhythmic Types

Of the mutationally defined rhythm genes in Drosophila melanogaster, period (per) has been studied the most. We have molecularly characterized three older per mutants—perT, perClk, and per04—along with a novel long-period one (perSLIH). Each mutant is the result of a single nucleotide change. perT, perClk, and perSLIH are accounted for by amino acid substitutions; per04 is altered at a splice site acceptor and causes aberrant splicing. perSLIH exhibits a long period of 27 hr in constant darkness and entrains to light/dark (L/D) cycles with a later-than-normal evening peak of locomotion. perSLIH males are more rhythmic than females. perSLIH's clock runs faster at higher temperatures and slower at lower ones, exhibiting a temperature-compensation defect opposite to that of perLong. The per-encoded protein (PER) in the perT mutant cycles in L/D with an earlier-than-normal peak; this peak in perSLIH is later than normal, and there was a slight difference in the PER timecourse of males vs. females. PER in per04 was undetectable. Two of these mutations, perSLIH and perClk, lie within regions of PER that have not been studied previously and may define important functional domains of this clock protein.

MUTANTS OF THE BIOLOGICAL CLOCK IN CHLAMYDOMONAS REINHARDI

ABSTRACT A genetic analysis of the biological clock in Chlamydomonas reinhardi has been initiated. Of six wild-type strains tested (3 mt+ and 3 mt−), five had periods close to 24 hr whereas one had a 21-hr period. Mutants with altered clock period have been isolated. The periods of 3 of these variant strains are temperature compensated. Genetic crosses involving a long-period mutant suggest that a single gene confers the long-period character, and in general clock-period length seems to be a useful phenotypic measure of alterations in the clock due to genetic differences. One phase mutant was found but its behavior was variable and the phase of the rhythm, relative to a light–dark transition which initiates the rhythm, does not seem to be reliable as a parameter of clock differences. No markers have yet been mapped.