Ronald J. Konopka

Reciprocal Behaviour Associated with Altered Homeostasis and Photosensitivity of Drosophila Clock Mutants

The circadian oscillators of genetically short–period and long–period Drosophila exhibit reciprocal behaviour in four distinct ways: (1) with respect to the dependence of period on temperature, (2) in the change of period during constant darkness after ten days of constant light, (3) in the change of period during the second ten days of darkness as compared with the period during the first ten days, and (4) in the period change resulting from exposure to low–intensity constant light. The homeostatic control of the dependence of period length on temperature is impaired in the mutants as compared with wild–type files. The normal Drosophila pacemaker may comprise two mutually coupled oscillators, whereas the mutants may represent a reduction in activity of one or the other constituent oscillator.

Effects of dosage alterations at the per locus on the period of the circadian clock of Drosophila

SummaryThe normal 24-h period of the circadian rhythms of locomotor activity and eclosion of Drosophila melanogaster is altered by changes in per gene dosage. Females with only one dose of per+ or pers (the 19-h short-period mutant allele) or per1 (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 pers 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 pers indicate that the hypermorphic phenotype of pers results from increased activity of the pers gene product rather than an overproduction of per+ product. This is the first report of such a mutant action in Drosophila.

Tyrosine and catecholamine metabolism in wild-type Drosophila melanogaster and a mutant, ebony

Abstract Microinjection of radioactive tyrosine, dopa, and dopamine into mature larvae of Drosophila revealed that the sclerotization pathway is similar but not identical to that in Calliphora : (a) tyrosine is converted to tyrosine-o-phosphate and not to dopa, and (b) the substrate N-acetyldopamine does not accumulate. Larvae of the mutant ebony appear to be similar to the wild type with respect to tyrosine, dopa, and dopamine utilization. About the time of eclosion, however, ebony has twice as much dopamine as normal. Some implications of this are discussed with reference to the mutant phenotype.

Circadian clock phenotypes of chromosome aberrations with a breakpoint at the per locus

SummaryThe circadian rhythm phenotypes of eight chromosome aberrations with a breakpoint in the region of the per locus (3B1-2) were analyzed. Two duplications and five deficiencies with a 3B1-2 breakpoint produce either a wild-type 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 period (31–39 h), rhythms that grade into arrhythmicity, or completely arrhythmic phenotypes. This is a unique phenotype that had not previously been observed for mutants at the per locus. 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 clock phenotypes of 3B1-2 chromosome aberrations, the three per mutant alleles, and per+ duplications suggest that mutations at the per locus shorten, lengthen, or eliminate periodicity by respectively increasing, decreasing, or eliminating per activity.

Mosaic Analysis of a Drosophila Clock Mutant

SummaryGynandromorphs that showed mosaicism for an X chromosome carrying a short-period (pers) circadian clock mutation and several visible mutations were produced by two different methods. A blastoderm fate map of cuticle markers as well as the focus of the clock mutation were constructed with the aid of a least-squares computer program. The focus location was consistent with a brain location for the clock. Some flies with mosaic heads had activity rhythms with both male and female components, suggesting that the oscillators in the two halves of the brain were of different genotype and could function independently.

Characterization of Andante, A New Drosophila Clock Mutant, and its Interactions with Other Clock Mutants

A new clock mutant, named Andante, has been identified on the X chromosome of Drosophila melanogaster. Andante lengthens the period of the circadian eclosion and locomotor activity rhythms by 1.5-2.0 hours. The phase response curves for the eclosion and activity rhythms, indicating light-induced phase shifts, show a similar degree of lengthening. Andante also lengthens the periods of other clock mutants, including Clock, and alleles of the period locus. Analysis of locomotor activity rhythms reveals that Andante is semi-dominant, and Andante rhythms are highly temperature compensated. The sine oculis mutation, which eliminates the outer visual system, has no effect on the period of Andante. Deficiency mapping indicates that Andante is located in the 1OE1-2 to 1OF1 region of the X chromosome, close to the miniature-dusky locus. Whereas Andante flies have a dusky wing phenotype, dusky flies do not have an Andante clock phenotype.

Mosaic analysis in the Drosophila CNS of circadian and courtship-song rhythms affected by a period clock mutation.

The period gene in Drosophila melanogaster controls not only daily rhythms associated with adult emergence and behavior, but also a much higher frequency rhythm that accompanies the males courtship song. This oscillation in the rate of sound production (normal period, ca. one minute) is either sped up (by perS), slowed down, or eliminated in the three classic per mutants. We have conducted a mosaic analysis in which both lovesong and circadian locomotor cycles were examined in a series of flies that were each part perS and part per+. Consistent with previous studies, the focus for per control of the adults circadian rhythm of locomotion was found to be in the brain. However, several mosaic individuals were found to exhibit a mutant locomotor rhythm but a wild-type song cycle, or vice-versa, enabling us provisionally to map the song-rhythm focus to the thoracic ganglia. That per is expressed only in glial cells in the thoracic nervous system and, in general, mediates slow (hour-by-hour) fluctuations in the levels of its own products are discussed from the standpoint of the current mosaic mapping results and the renewed focus they bring to the genes influence on an ultradian rhythm.

Effects of a Clock Mutation on the Subjective Day — Implications for a Membrane Model of the Drosophila Circadian Clock

The fly brain, like the human brain, possesses an oscillatory system which enables the brain to form a model of the 24 hour cycle in the external environment. This oscillator is termed circadian, since it continues to oscillate in the absence of environmental cues with a period of about a day.1 The molecular mechanism of the circadian oscillator in any organism is as yet unknown. Since the fruit fly is an excellent organism for the study of the effects of mutations on nervous system function, chemically induced mutations affecting circadian rhythmicity were isolated.2,3 These mutations behave as alleles of a single genetic locus, per,which has been mapped by means of deletions to the 3B1-2 region of the X chromosome.2–4 They affect the periodicity of the eclosion rhythm and the adult locomotor activity rhythm in a similar manner: the short-period allele, per s ,shortens the period from 24 hours in wild-type to 19 hours in the mutant; the long-period allele, per 1 , lengthens the period to 29 hours; and an arrhythmic allele, per o , produces aperiodic eclosion and activity.

Neurogenetics of Drosophila Circadian Rhythms

The isolation of single-gene mutations has proved to be a useful tool in investigating the molecular basis of cellular processes. Although the discovery that living organisms possess endogenous oscillators with a period of about a day (circadian) was made more than two centuries ago, the molecular nature of these oscillators is still unknown. In an effort to understand the genetic control of circadian rhythmicity, as well as to provide a means of identifying a molecule that may be a component of the underlying oscillator, my laboratory is studying the genetics, physiology, and behavior of Drosophila that bear chemically induced mutations which alter the periodicity of the circadian eclosion and adult locomotor activity rhythms. This paper summarizes some of the results of these investigations.

Genetics and Development of Circadian Rhythms in Invertebrates

The scope of this review includes the developmental ontogeny and genetics of the driving oscillator and overt rhythms in invertebrates. The discussion is generally confined to meta-zoan organisms, except in cases where comparison with data from lower organisms is useful. The terms pacemaker and oscillator are usually used in the singular, although the actual physiological pacemaker may be made up of components—a population of coupled oscillators—or, at least, represented bilaterally in the two hemispheres of the brain. Only true circadian rhythms—those that persist in constant conditions—are covered; diel rhythms, which are expressed in LD but not in constant conditions, are not discussed.