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A Garen

Publications and source records attributed to A Garen.

At least 37 records · Page 2Linked to original sources
PubMed1986

Molecular organization and expression of the genetic locus glued in Drosophila melanogaster.

The Glued locus of Drosophila melanogaster is genetically defined as the functional unit which is affected by the dominant Glued mutation Gl. Genomic DNA was cloned from the region of the Glued locus, at 70C2 on chromosome 3, by using a P element insertion in the region as a molecular marker. Three genes encoding polyadenylated transcripts were detected within a 30-kilobase span of the cloned DNA. The gene nearest the P element insertion site was identified as a Glued gene on the basis of alterations in its DNA and encoded transcript associated with the Gl mutation and with reversions of Gl which eliminate the dominant effect by inactivation of the mutant allele. Expression of the wild-type Gl+ gene is temporally regulated during development; the amount of the encoded transcript is highest in the embryonic stage, decreasing in the first and second larval instars, and then increasing in the third instar and pupal stages. There is a maternal contribution of the Gl+ transcript to the embryo, which probably accounts for the maternal lethal effect of Glued mutations on early development. In situ hybridizations of Gl+ DNA to RNA in tissue sections showed that the Gl+ transcript is present in virtually all tissues of the embryo, late larva, and pupa. The general distribution of this transcript is consistent with genetic evidence indicating that the Glued locus controls a generally essential cell function (P. J. Harte and D. R. Kankel, Genetics 101:477-501, 1982). Different Glued mutations produce distinct phenotypic effects, including adults with severe visual defects, larvae lacking imaginal discs, and early lethality. These diverse mutant phenotypes are discussed in terms of quantitative changes in the Glued function. Closely adjacent to Gl+ is another gene which is transcribed in a divergent direction and expressed coordinately with Gl+ throughout Drosophila development. It remains to be determined whether this gene is also involved with the Glued function.

Animals↗
PubMed1985

Molecular genetics of a transposon-induced dominant mutation in the Drosophila locus Glued.

The organization of the Drosophila locus Glued containing the dominant allele Gl was shown to differ from that of the normal locus by an insertion of a 9-kilobase-pair DNA segment near the 3' end of a transcribed region. The insertion causes the formation of a truncated polyadenylylated transcript of 5.1 kilobases instead of the normal 6.0 kilobases. The inserted DNA segment has the properties of a transposon and was identified by its corresponding restriction map as B104, which is a retrovirus-like transposon with direct terminal repeats. B104 appears to be oriented in Gl with the same polarity of transcription as Gl. The truncated Gl transcript terminates prematurely inside the 5' terminal repeat of B104, in the region of a putative polyadenylylation signal. We discuss the general implications of this finding for transposon- and retrovirus-induced mutagenesis and for the origin of dominant mutations.

Alleles↗
PubMed1984

Mutations affecting functions of the Drosophila gene glued.

Glued mutations in Drosophila comprise an essential complementation group with complex developmental effects. The original Glued mutation (Gl) has dominant nonlethal effects in heterozygous flies, principally on the morphogenesis of the visual system. Gl also has a recessive lethal effect early in development. Mutations that reverse the dominant visual effects of Gl (GlR mutations) were induced by gamma-radiation or by insertions of the transposable P element. The GlR(G) mutations induced by gamma-radiation do not reverse the lethal effect of Gl; these appear to be null mutations, some of which (and possibly all) delete segments of the Glued region. The GlR(P) mutations induced by insertion of the P element also reverse concomitantly a recessive lethal effect of Gl, suggesting that both the recessive and dominant effects are controlled by the same gene. The reversal of a lethal effect of Gl by the P element is remarkable, since it indicates that an essential gene function can be restored by insertion of unrelated DNA. Another class of lethal Glued mutations was induced in the normal Gl+ strain by ethyl methanesulfonate (EMS). The EMS mutations belong to the same essential complementation group as Gl, but do not have the strong dominant effects of Gl on the visual system. The GlR(P) mutations provide a molecular marker for the Glued gene, which was used to map the gene to the 70C2 band of chromosome 3L by in situ hybridization of a P element probe to polytene chromosomes from the GlR(P) strains and also to isolate clones of Glued genomic DNA for molecular studies of the normal gene and the various Glued mutations.

Animals↗
PubMed1983

Selective gene expression induced by ecdysterone in cultured fat bodies of Drosophila.

Expression of the LSP-2 and P1 genes was induced in cultured fat bodies of Drosophila third-instar larvae by supplementing the culture medium with ecdysterone. The fat bodies were isolated from ecdysterone-deficient larvae of the temperature-sensitive mutant ecd1, which were shifted from the permissive to the restrictive temperature either at the beginning of the third instar for the detection of LSP-2 induction or several hours later for the detection of P1 induction. During normal larval development, the LSP-2 gene is expressed before the P1 gene, and this order is also observed in the cultured fat bodies. Induction was demonstrated by increased amounts of LSP-2 and P1 transcripts in the ecdysterone-supplemented fat bodies. The amount of P1 transcript was determined by two methods: one involved measuring the hybridization of a labeled P1 DNA probe to total fat body RNA; the other involved labeling the newly synthesized RNA in nuclei isolated from cultured fat bodies and measuring the hybridization of the labeled RNA to P1 DNA. Only the second method was used for the LSP-2 transcript because the earlier expression of the LSP-2 gene results in a measurable accumulation of the transcript in the fat bodies before ecdysterone supplementation. The maximal level of P1 induction was reached within 2 hr after supplementation, and the induction was not affected by a concentration of cycloheximide that strongly inhibited total protein synthesis, suggesting that ecdysterone acts directly on the P1 gene rather than indirectly by inducing formation of proteins required for the subsequent induction of P1. Ecdysterone appears to function normally in the cultured fat body system because the LSP-2 and P1 genes are induced in culture in the same order as in vivo and a third gene, G12, that is not induced in fat bodies in vivo also is not induced in culture.

Adipose Tissue↗
PubMed1982

Developmentally regulated gene expression in Drosophila larval fat bodies.

During third-instar larval development of Drosophila melanogaster, the fat body tissue synthesizes six major methionine-containing polypeptides, three of which are the alpha, beta, and gamma subunits of the hexameric larval serum protein LSP-1, a fourth is the single subunit of the hexameric larval serum protein LSP-2, and the other two are polypeptides P6 and P1. Genomic DNA clones of the six structural genes for the polypeptides were isolated and characterized. Each gene maps by in situ hybridization at a single chromosomal site and appears to be present as a single copy in the genome. The LSP-1 and LSP-2 genes show striking regulatory similarities: The LSP-1 beta and gamma transcripts are first detected in fat bodies within an hour after the second molt, and the LSP-1 alpha and LSP-2 transcripts a few hours later; the four transcripts are subsequently maintained at high levels during most of the third instar and rapidly decrease shortly before pupariation. Ecdysterone increases the levels of at least three of the four LSP transcripts in the fat bodies when ecdysterone-deficient larvae from the temperature-sensitive mutant ecd1 are supplemented with the hormone. The regulatory characteristics of the P6 and P1 genes differ in several ways from those of the LSP genes. Expression of the P6 and P1 genes begins later than the LSP genes, and the levels of the transcripts remain high at the end of the third instar after the LSP transcripts have markedly decreased. Ecdysterone increases the level of the P1 transcript, but not of the P6 transcript, in ecdysterone-deficient ecd1 larvae.

Adipose Tissue↗
PubMed1981

Constancy of somatic DNA organization in developmentally regulated regions of the Drosophila genome.

The purpose of this study was to test for the occurrence of changes in the organization, modification, or selective amplification of six developmentally regulated regions of genomic DNA during Drosophila development. Five of the regions contain structural genes, each of which maps at a single chromosomal site; the sixth region contains a dispersed segment that maps at about 30 different sites and appears to be transposable. The RNA transcripts and encoded proteins of the structural genes are major components of the fat body tissue in late third-instar larvae, in contrast to other larval tissues and young embryos in which the transcripts and proteins are hardly detectable. The dispersed segment shows the reverse developmental regulation: the amount of transcript is relatively high in young embryos and low in larval fat bodies. The test for changes in genomic DNA associated with the regulated expression of the six regions was based on comparative restriction mapping of the DNA from these sources. Genomic clones containing the transcribed and also flanking regions of DNA were used as probes to determine the positions of the complementary restriction fragments after electrophoresis in agarose gels. Each test, which involved digesting the genomic DNA samples with one of the endonucleases and probing with one of the clones, produced identical restriction maps for the different samples. The tests are capable of detecting changes in the organization of the cloned regions resulting from addition or removal either of endonuclease cleavage sites or of segments of DNA located between cleavage sites. Because the activities of several of the endonucleases, and probably all, are sensitive to methylation of one of the bases in the DNA recognition sequence, certain modifications of the cloned regions by methylation could also be detected. Although it is not certain that genomic reorganization or modification would have been detected by these tests, the number of endonucleases used was sufficient to provide persuasive evidence that such changes did not occur. Furthermore, the quantitative as well as qualitative similarities of the restriction maps in each test indicated that there was no significant selective amplification of the DNA within the cloned regions.

Adipose Tissue↗
PubMed1978

Ecdysone-inducible functions of larval fat bodies in Drosophila.

Late in the third instar larval stage of Drosophila melanogaster, the titer of the steroid hormone ecdysone increases sharply. This increase is blocked in the temperature-sensitive mutant ecd(1) after a temperature shift from 20 degrees C to 29 degrees C. The mutant was used to prepare three samples of late third instar larvae with different titers of ecdysone; the titer was low in one sample because of an earlier temperature shift, high in a second sample because the larvae were subsequently transferred to ecdysone-supplemented food, and also high in a third sample that was kept at 20 degrees C, providing a control for normal development. The effect of the high titer of ecdysone on proteins of the larval fat bodies was examined by comparing two-dimensional gel electrophoresis patterns of total proteins in stained gels. There were proteins at five positions in the gels for the high-ecdysone samples that were not detected at the corresponding positions in the gel for the low-ecdysone sample. The effect of ecdysone on these proteins was further studied by injecting [(35)S]methionine into the larvae at both early and late third instar stages, in order to label proteins synthesized before and after the increase in ecdysone titer. The results indicate that ecdysone induces two major responses in the fat bodies; certain proteins that were synthesized earlier in the fat bodies and secreted into the hemolymph are incorporated back into the fat bodies, and other proteins are newly synthesized. Attempts to induce prematurely the synthesis of the new proteins by exposing early third instar larvae to exogenous ecdysone were unsuccessful, suggesting that development must proceed further before the fat bodies can respond to ecdysone. By in vitro translation of RNA isolated from fat bodies of low-and high-ecdysone samples of larvae, it was shown that ecdysone greatly increases the amount of translatable messenger RNA for one of the newly synthesized proteins. A clone of DNA complementary to the induced messenger RNA has been isolated from a population of lambda bacteriophage carrying segments of the Drosophila genome. Using the cloned DNA to measure amounts of complementary poly(A)-RNA in the fat bodies by DNA.RNA hybridization, we detected about 50 times more complementary poly(A)-RNA in the high-ecdysone sample of larvae than in the low-ecdysone sample. This finding provides direct evidence that ecdysone induces an increase in the amount of the messenger RNA. The ecdysone-induced appearance of a major messenger RNA in late third instar larval fat bodies represents a developmental response to ecdysone that appears to be gene-specific, tissue-specific, and stage-specific, and it has exceptionally favorable features for further molecular studies of the control of gene expression by a steroid hormone.

Adipose Tissue↗
PubMed1977

Roles of ecdysone in Drosophila development.

A temperature-sensitive lethal mutant of Drosophila melanogaster called ecd(1) becomes deficient in ecdysone, as measured by a radioimmunoassay, when there is a shift in temperature from 20 degrees to 29 degrees at various stages of development. Associated with the ecdysone deficiency at 29 degrees , there are abnormalities in larval and imaginal development and the adult functions. When the shift occurs early in third-instar stage, the mutant larvae grow to full size but fail to pupariate, and instead remain living larvae for as long as 3 weeks. These larvae, which have only about 5% as much ecdysone as the wild-type at the time of pupariation, can be induced to pupariate at 29 degrees by ecdysone in their food, indicating that the pupariation block results from an ecdysone deficiency. A shift to 29 degrees later in the third-instar stage does not prevent pupariation of the mutant, but the imaginal discs fail to complete differentiation, although the discs can differentiate at 29 degrees after transplantation to the normal environment of a wild-type host. A shift to 29 degrees early in the first-instar stage blocks a subsequent rise in ecdysone titer and results in extensive developmental defects. Mutant adults become sterile at 29 degrees , and the ecdysone titer in the females concomitantly decreases to 13% of the wild-type value. Mutant larval ovaries transplanted to wild-type female hosts continue to develop and produce competent eggs at 20 degrees , but when the adult hosts are put at 29 degrees the transplanted ovaries become sterile, suggesting that the ecdysone needed for female fertility is synthesized autonomously by ovarian tissue. In contrast to these effects of a shift to 29 degrees during larval, pupal, and adult stages, there is a normal increase in ecdysone titer and normal development in mutant embryos grown at 29 degrees . The insensitivity of the embryo to the ecd(1) mutation might be due to a maternal contribution of components needed for ecdysone synthesis during the embryonic stage.

Journal Article↗
PubMed1974

Genetic control of imaginal disc development in Drosophila.

Many of the functions required for formation of the imaginal discs of Drosophila melanogaster larvae, from which adult structures are derived, are disc-specific and not required for formation of other larval tissues. Mutants blocked in disc-specific functions can produce mature viable larvae, indicating that larval development is not dependent on concomitant disc development. Some of the mutant larvae have no detectable discs (discless mutants), and other have small discs that cannot differentiate into adult structures (small disc mutants). From the results of genetic complementation and mapping experiments with such mutants, it was estimated that the genome of D. melanogaster contains around a thousand complementation groups, or about a fifth of all complementation groups in the genome, that are essential specifically for the development of all the discs. The developmental defects in some of the disc mutants appear to involve autonomous functions of the imaginal cells, and in other mutants functions provided by the larval environment to support disc development. This distinction was made on the basis of two functional tests. The purpose of one of the tests was to detect the presence in young embryos of determined imaginal cells capable of differentiating after transplantation to a wild-type host; the other test measured the capacity of early third-instar larvae to act as hosts for the further development of immature discs transplanted from a wild-type donor. Three discless mutants that were tested in this way appeared to be defective in autonomous functions of the imaginal cells, since the embryos contained no imaginal cells that could be detected in the first test, whereas the larvae, although devoid of discs, showed a normal capacity to support disc development in the second test. One of the small disc mutants tested was defective in a larval rather than an imaginal cell function, since the embryos had a normal complement of functional imaginal cells, whereas the larvae were incapable of supporting disc development. Thus, both types of disc-specific functions are essential for normal disc development.

Animals↗
PubMed1972

Repair of the lethal developmental defect in deep orange embryos of Drosophila by injection of normal egg cytoplasm.

The eggs produced by deep orange females (dor/dor) of Drosophila melanogaster have a defect that causes early death of the deep orange embryos derived from these eggs. Ovaries transplanted from deep orange females to normal female hosts continue to produce defective eggs, showing that the dor mutation directly affects an ovarian function. In heterozygous embryos (dor(+)/dor) derived from eggs of deep orange females, the presence of a paternal dor(+) gene enables normal development to occur in about half of the embryos. Thus, the egg defect caused by the dor mutation is repairable after fertilization by the action of a dor(+) gene. The deep orange egg defect has also been repaired by injection of cytoplasm from unfertilized normal eggs into deep orange embryos at the syncitial preblastoderm stage of development. About one-third of the injected deep orange embryos were able to continue their development to an advanced stage of embryogenesis. This developmental response can serve as a bioassay for the identification of the defective component in eggs of deep orange females.

Animals↗
PubMed1971

Nonsense fragments.

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Bacterial Proteins↗
PubMed1971

Imaginal disc abnormalities in lethal mutants of Drosophila.

Late lethal mutants of Drosophila melanogaster, dying after the larval stage of development, were isolated. The homozygous mutant larvae were examined for abnormal imaginal disc morphology, and the discs were injected into normal larval hosts to test their capacities to differentiate into adult structures. In about half of the mutants analyzed, disc abnormalities were found. Included among the abnormalities were missing discs, small discs incapable of differentiating, morphologically normal discs with limited capacities for differentiation, and discs with homeotic transformations. In some mutants all discs were affected, and in others only certain discs. The most extreme abnormal phenotype is a class of "discless" mutants. The viability of these mutant larvae indicates that the discs are essential only for the development of an adult and not of a larva. The late lethals are therefore a major source of mutants for studying the genetic control of disc formation.

Abnormalities, Drug-Induced↗