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.

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.

Hybridization of tRNAs of Drosophila melanogaster to polytene chromosomes.

Highly purified tRNAs from Drosophila melanogaster were iodinated with 125I and hybridized to squashes of polytene chromosomes of Drosophila silivary glands followed by autoradiography to localize binding sites. Most tRNAs hybridize strongly to more than one site and weakly to one or more additional sites. The major sites for various tRNAs are the following: tRNA2Arg, 42A, 84F1,2; tRNA2Asp, 29DE; tRNA3Gly, 22BC, 35BC, 57BC, tRNA2Lys, 42A, 42E; tRNA5Lys, 84AB, 87B; tRNA2Met, 48B5-7, 72F1-2, 83F-84A; tRNA3Met, 46A1-2, 61D1-2, 70F1-2; tRNA4Ser, 12DE, 23E; tRNA7Ser, 12DE, 23E; tRNA3aVal, 64D; tRNA3bVal, 84d3-4, 92b1-9; tRNA4Val, 56D3-7, 70BC.

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.

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.

The localization of transfer RNA5Lys genes in Drosophila melanogaster.

Transfer RNA(5) (Lys) was isolated and purified from Drosophila melanogaster. It was iodinated in vitro with sodium [(125)I]iodide and hybridized in situ to the polytene salivary gland chromosomes from Drosophila. Autoradiographs exposed three to four weeks allowed the localization of this tRNA to the right arm of chromosome 2 between bands 48F and 49A.

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. 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.

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.

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.