Genetic Analysis of the Circadian Clock System of Drosophila melanogaster

Citation

Smith, Randall Forrest (1982) Genetic Analysis of the Circadian Clock System of Drosophila melanogaster. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/9rwg-p020. https://resolver.caltech.edu/CaltechTHESIS:05172018-103149078

Abstract

The circadian rhythm phenotypes of eight chromosome aberrations with a breakpoint in the region of the per locus (3B1-2) of Drosophila melanogaster have been analyzed. Two duplications and five deficiencies with a 3B1-2 breakpoint produce either a wild-type (approx. 24-h period) or an arrhythmic clock phenotype while one translocation with a 3B1-2 breakpoint, T(1;4)JC43, produces locomotor-activity rhythms with either very-long periods (31-39 hr), rhythms that grade into arrhythmicity, or completely arrhythmic phenotypes. The clock phenotypes of 3B1-2 chromosome aberrations suggest that arrhythmicity results from the total lack of per function while long-period phenotypes result from a reduction, but not complete elimination, of per activity. An extensive complementation analysis of 3B1-2 chromosome aberrations and per mutant alleles provided no compelling evidence for genetic complexity at the per locus. This is in contrast to the report of Young and Judd (1978). Analysis of both the locomotor-activity and eclosion phenotypes of 3B1-2 chromosome aberrations did not uncover differences in the genetic control of these two rhythms.

The normal 24-h period of the circadian rhythms of locomotor activity and eclosion of Drosophila is shown to be altered by changes in per gene dosage. Females with only one dose of per⁺ or per^s (the 19-h short-period mutant allele) or per^l (the 29-h long-period mutant allele) have periods which are about 1-2 h longer than the corresponding females with 2 doses. Females with 3 doses of per⁺ and males with 2 doses of per⁺ or per^s have periods which are 1/2 to 1 h shorter than the corresponding individuals without the extra dose. Males with three per⁺ doses have periods which are about 1.5 h shorter than wild-type males; additional per⁺ doses do not shorten period further. The observation that decreased per dosage lengthens period while increased dosage shortens period suggests that the long- and short-period mutations alter period by respectively decreasing and increasing per gene or gene product activity. The per⁺ dosage results and the complementation behavior of per^s indicate that the hypermorphic phenotype of per^s results from increased activity of the per^s gene product rather than an overproduction of per⁺ product. This is the first report of such a mutant action in Drosophila.

By screening mutagenized sex-linked and autosomal stocks for ones in which the normal period or phase of the circadian rhythm of eclosion (adult emergence) has been altered, a new X-linked clock mutant has been isolated which lengthens the normal 24-h period of both the the eclosion and adult locomotor-activity rhythms to about 25.5 h. This mutant, which we have named Andante (And), is not an allele of the per locus; recombination and deficiency mapping has placed the Andante locus at a separate site between polytene chromosome bands 10E2 and 10F1 (tentatively at 10E3, just proximal to the m-dy complex at 10E2-3). Andante, like all of the per mutant alleles, has a semi-dominant effect on period. The eclosion rhythm of Andante, like wild-type, has a low-amplitude (Type 1) phase-resetting response to light pulses, but compared to wild-type the Andante phase-resetting curve (PRC) is lengthened by 1-2 h per cycle.

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