Temperature-sensitive mutations in Drosophila melanogaster. XVII. Heat- and cold-sensitive lethals on chromosome 3.

Ethyl methanesulfonate-treated third chromosome of Drosophila melanogaster were tested for the presence of dominant and recessive temperature-sensitive lethal mutations at 17 degrees , 22 degrees and 29 degrees C. Out of 1,176 chromosomes tested, no dominant ts lethals, 21 heat-sensitive, 22 cold-sensitive and 10 heat-cold-sensitive lethals were recovered. Heat-cold sensitivity was produced by a single mutation in all cases. Sixty-two percent of the ts lethals were fertile as homozygotes in both sexes. Surprisingly, 88% of the ts lethals mapped between st and Sb, a region straddling the centromere and estimated to comprise 12.9% of the genetic length and 55% of the physical length of chromosome 3. All but one of the heat- and cold-sensitive lethals complemented with each other at their respective restrictive temperatures.

Temperature-sensitive mutations in Drosophila melanogaster. XII. The genetic and developmental effects of dominant lethals on chromosome 3.

Out of 25,000 EMS-treated third chromosomes examined, ten dominant temperature-sensitive (DTS) lethal mutations which are lethal when heterozygous at 29 degrees C but survive at 22 degrees C were recovered. Seven of the eight mutations mapped were tested for complementation; these mutants probably define eight loci. Only DTS-2 survived in homozygous condition at 22 degrees C; homozygous DTS-2 females expressed a maternal effect on embryonic viability. Two of the mutant-bearing chromosomes, DTS-1 and DTS-6, exhibited dominant phenotypes similar to those associated with Minutes. Each of the seven mutants examined exhibited a characteristic phenotype with respect to the time of death at 29 degrees C and the temperature-sensitive period during development. Only DTS-4 exhibited dominant lethality in triploid females.

Temperature-sensitive mutations in Drosophila melanogaster. IX. Dominant cold-sensitive lethals on the autosomes.

Ethyl methanesulfonate-treated autosomes were screened for the presence of dominant cold-sensitive (DCS) lethal mutations in Drosophila melanogaster. None was found among 6,552 treated and 168 untreated third chromosomes. Twenty-three DCS-L chromosomes which caused death at 17 degrees C but survived at 22 degrees C and 29 degrees C were recovered from 5,046 mutagenized chromosome 2's.-The DCS-L mutations all mapped around dp and appeared to be functionally allelic. Lethality of heterozygotes for most of the DCS-L's occurred over a prolonged interval from the embryonic through the larval instars. Prolonged incubation at 17 degrees C did not demonstrate any maternal effect on zygotic survival.

Genetic and developmental analysis of a temperature-sensitive minute mutation of Drosophila melanogaster.

A temperature-sensitive (ts) third chromosome Minute (M) mutation, designated Q-III, has been recovered and characterized. Q-III heterozygotes raised at 29 degrees exhibit all of the dominant traits of M mutants including small bristles, rough eyes, prolonged development, reduced viability and interactions with several unrelated mutations. Q-III homozygotes raised at 29 degrees are lethal; death occurs primarily during the first larval instar. When raised at 22 degrees, Q-III heterozygotes are phenotypically normal and Q-III homozygotes display moderate M traits. In addition, Q-III elicits ts sterility and maternal-effect lethality. As is true of M lesions, the dominant traits of Q-III are not expressed in triploid females raised at 29 degrees. Complementation tests suggest that Q-III is a ts allele of M(3)LS4, which is located in 3L near the centromere.--Reciprocal temperature-shift experiments revealed that the temperature-sensitive period (TSP) of Q-III lethality is polyphasic, extending from the first instar to the latter half of pupation. Heat-pulse experiments further resolved this into two post-embryonic TSPs: one occurring during the latter half of the second larval instar, and the other extending from the larval/pupal boundary to the second half of pupation. In addition, heat pulses elicited a large number of striking adult phenotypes in Q-III individuals. These included pattern alterations such as deficiencies and duplications and other morphological defects in structures produced by the eye-antennal, leg, wing and genital imaginal discs and the abdominal histoblasts. Each defect or pattern alteration is associated with a specific TSP during development.--We favor the interpretation that most of the major Q-III defects, particularly the structural duplications and deficiencies, result from temperature-induced cell death in mitotically active imaginal anlagen, while the small macrochaete phene probably results from the direct effects of Q-III on bristle synthesis. The hypothesis that the Q-III locus specifies a component required for protein synthesis is discussed, and it is concluded that this hypothesis can account for the pleiotropy of Q-III, and that perhaps it can be extended to M loci in general.

Genetic control of insect population. I. Cage studies of chromosome replacement by compound autosomes in Drosophila melanogaster.

A genetic method for insect control was evaluated using the test organism, Drosophila melanogaster. The technique involved the displacement under a system of continuous reproduction, of standard strains by those carrying compound autosomes. The eradication of the replacements could subsequently be achieved through the use of temperature-sensitive lethal mutations.-While certain compound autosome strains failed to displace standards in population cages, even at the initial release ratio of 25:1, others were highly successful. Indeed, for some strains when the ratio of compounds to standards was as low as 9:1, the population rapidly went to fixation in favor of the compound line.-Hatchability was found to be an insufficient index of fitness to estimate the initial ratios of compounds to standards that would guarantee fixation of the former. Differences in other fitness components, such as development time, were detected that could seriously modify displacement, especially with continuous overlapping generations. The importance of examining the fitness of various compound lines and selecting the most competitive in cages, prior to field tests, cannot be overemphasized.

The interaction of two complex loci, zeste and bithorax in Drosophila melanogaster.

It has been found that certain alleles of the zeste locus (z(a) 1-1.0) have no phenotype of their own, but interact with certain alleles at the bithorax locus (bx 3-58.8). This interaction takes the form of an enhancement of the homeotic bx phenotype to a more extreme form-i.e., the metathorax is transformed into mesothorax in varying degrees depending on the bx allele used. This enhancement is somewhat reminiscent of the transvection effect described by Lewis (1954). The characterization of the interaction thus far has shown that the enhancement only effects bx alleles which arise spontaneously, whereas the origin of the z(a) allele is unimportant. The gene claret nondisjunctional was used for the production of gynandromorphs which showed that the enhancing ability of z(a), like the eye pigment change caused by z, is autonomous. The enhancement of one specific allele (bx(34e)), which is temperature-sensitive, has allowed a delineation of the temperature-sensitive period of the bithorax locus to a period extending from the middle of the second larval instar to the middle of the third larval instar. These results, as well as those of other enhancer and suppressor systems in Drosophila, have revealed the possibility of the involvement of heterocyclic compounds in the control of cell determination and fate in Drosophila melanogaster.

Temperature-sensitive mutations in Drosophila melanogaster. 8. The homeotic mutant, ss a40a .

There exists in Drosophila a class of mutations called "homeotic" that cause changes in determination of the imaginal discs. The homeotic mutant, ss(a40a), was found to have a temperature-sensitive transformation of the arista segment of the antennal complex to a tarsus of the leg. In a selected stock penetrance was complete, so that at 29 degrees C normal aristae were produced, whereas at 17 degrees C complete tarsi developed in all flies. "Temperature-shift" studies revealed a temperature-sensitive period in the third larval instar. The temperature-initiated action of ss(a40a) does not appear to result from a simple wave or gradient of determination passing through the disc. Shifts up during the temperature-sensitive period yielded leg tissue proximally, which increased distally with progressively later shifts. Shifts down yielded leg tissue at the aristal base, which retreated with later shifts.

Temperature-sensitive mutations in Drosophila melanogaster. V. A mutation affecting concentrations of pteridines.

A temperature-sensitive ras allele has an effective lethal phase at 29 degrees C about 12 hr after pupation and a temperature-sensitive period for lethality beginning midway through the third larval instar and ending around pupation. The mutation also alters the quantity of pteridines present in the eyes, testes, and Malpighian tubules at 29 degrees C. The temperature-sensitive period for pigment production in the Malpighian tubules occurs in the egg and first instar larvae, and in eyes and testes after pupation. The demonstrated autonomy of the mutant in the eyes implies the tissue-specific functioning of the gene. We suggest that the different temperature-sensitive periods for a single mutation indicate tissue-specific activation of a gene at different times during development, although the possibility of activation of preformed polypeptides has not been eliminated.

Temperature-sensitive mutations in Drosophila melanogaster. IV. A mutation affecting eye facet arrangement in a polarized manner.

Drosophila melanogaster females heterozygous for the mutation N(60g11) have wild type eyes when raised at 29 degrees C but a disrupted arrangement of facets and extra bristles at 21 degrees C. Shifts of cultures from one temperature to the other at different stages in development revealed that facet arrangement is altered by temperature during the third larval instar. The facet pattern is affected in a vertical wave that proceeds anteriorly from the posterior rim of the eye. The role of the Notch locus in development is briefly discussed.

The effects of increased temperature on electroretinograms of temperature-sensitive paralysis mutants of Drosophila melanogaster.

Mutations within the shibire locus of Drosophila melanogaster are non-complementing alleles which result in reversible paralysis at 29 degrees but retention of normal locomotor behavior at 22 degrees . Electroretinograms of six of the mutants have been recorded at various temperatures. Two changes occurred in the electroretinograms of flies carrying most of the alleles at high temperature: they lost the "on"- and "off"- transients of the normal electroretinogram, and the fast decay of the receptor potential was attenuated. For flies with four of the alleles, a base-line oscillation was also observed. Analysis of electroretinograms of mosaic shibire flies indicates that the loss of the transients can be attributed to both a pre-synaptic and a post-synaptic effect.

Temperature-sensitive mutations in Drosophila melanogaster. 3. Dominant lethals and semilethals on chromosome 2.

Dominant temperature-sensitive lethal and semilethal (DTS-L) mutations induced by ethyl methanesulfonate have been recovered in chromosome 2 of Drosophila melanogaster. The 19 (0.39% of the chromosomes screened) characterized had greater than 65 per cent viability at 22 degrees +/- 2 degrees C and less than 5 per cent at 29 degrees +/- 0.5 degrees C. Fifteen of the DTS-L's map genetically as point mutants, one appears to be a synthetic lethal, and the remaining three yielded sterile females. Ten different DTS mutants had a high survival in triploid females at 29 degrees C. Eleven DTS-L's were found to map in the same genetic region (dp-b). All behaved as recessive lethals at 22 degrees C and failed to survive at 22 degrees C when combined with mutants 3 and 12. Crosses of the 11 mutants in all possible pairwise combinations yielded a circular complementation map with a side branch. The effective lethal phases and temperature-sensitive periods during development were determined for 15 of the mutants.

Population control of caged native fruitflies in the field by compound autosomes and temperature-sensitive mutants.

A genetic technique for insect population control has been tested in cages under field conditions at two different locations in British Columbia. The method entails the population replacement of standard insects by those bearing compound autosomes using the principle of negative heterosis, thus permitting control or elimination through conditional mutations. Both native- and laboratory-derived compound strains of the fruitfly Drosophila melanogaster were tested in population cages against standards in the laboratory and at the two field sites. Those compound-bearing insects originating from the wild were the most successful, both in the laboratory and the field, in displacing standards from the cages down to a minimum initial ratio of 5 compounds to 1 standard. The importance is stressed of collecting strains from the wild, and performing the necessary genetic manipulations as rapidly as possible, prior to releasing the rearrangement in the field for control purposes.

Behavioral mutants of Drosophila melanogaster. III. Isolation and mapping of mutations by direct visual observations of behavioral phenotypes.

Sex-linked behavioral mutants were induced in Drosophila melanogaster with ethyl methanesulfonate (EMS) and isolated by direct visual observation of abnormal phenotypes. The four behavioral phenotypes used were flight-reduction, hyperactivity, hypoactivity and stress-sensitivity, and are easily discernable in either single or small populations of mutant flies. In one screen, forty-two behavioral mutants were recovered from strains derived from 800 mutagen-treated X chromosomes In a second screen, 139 behavioral mutants were obtained from 2369 X chromosomes. The high rate at which behavioral mutants were recovered in the second screen, when compared to new visibles (28) and new temperature-sensitive lethals (124), suggests that the isolation of behavioral mutations on the autosomes of Drosophila and in the genomes of larger insects should be practical.