Genetic analysis of an intersex allele (ix5) that regulates sexual phenotype of both female and male Drosophila melanogaster.
TL;DR: The results, taken together with those of McRobert & Tompkins (1985), indicate that the ix+ gene also functions in male sex determination, and is likely to be involved in spermatogenesis.
Abstract: An allele of intersex (ix5) of Drosophila melanogaster has been characterized. The genetic analysis of the allele demonstrated that like other point mutations of ix, the ix5 allele also transformed diplo-X individuals into intersexes. The ix5 mutation also affects the arrangement of sex comb bristles on the forelegs of males, although they had morphologically nearly normal male genitalia. They often fail to display a sustained pattern of courtship activity when tested. Orcein-stained squash preparations of testes from ix5 males revealed a defect in spermatogenesis. Our results, taken together with those of McRobert & Tompkins (1985), indicate that the ix+ gene also functions in male sex determination.
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TL;DR: The results have been interpreted to have suggested that Lhr suppresses the lethality of hybrids by regulating functional activities of the X chromosome(s) for dosage compensation.
Abstract: The Drosophila simulans Lhr rescues lethal hybrids from the cross of D. melanogaster and D. simulans. We describe here, the phenotypes of Lhr dependent rescue hybrids and demonstrate the effects of Lhr on functional morphology of the salivary chromosomes in the hybrids. Our results reveal that the phenotypes of the ‘Lhr dependent rescued’ hybrids were largely dependent on the genetic background and the dominance in species and hybrids, and not on Lhr. Cytological examination reveal that while the salivary chromosome of ‘larval lethal’ male carrying melanogaster X chromosome was unusually thin and contracted, in ‘rescued’ hybrid males (C
mel
X
mel
Y
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; A
mel
A
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) the X chromosome showed typical pale staining, enlarged diameter and incorporated higher rate of 3H-uridine in presence of one dose Lhr in the genome. In hybrid males carrying simulans X chromosome (C
mel
X
sim
Y
mel
; A
mel
A
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), enlarged width of the polytene X chromosome was noted in most of the nuclei, in Lhr background, and transcribed at higher rate than that of the single X chromosome of male. In hybrid females (both viable, e.g., C
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X
mel
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; A
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and rescued, e.g., C
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X
mel
X
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; A
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), the functional morphology of the X chromosomes were comparable to that of diploid autosomes in presence of one dose of Lhr. In hybrid metafemales, (C
mel
X
mel
X
mel
X
sim
; A
mel
A
sim
), two dose of melanogaster X chromosomes and one dose of simulans X chromosome were transcribed almost at ‘female’ rate in hybrid genetic background in presence of one dose of Lhr. In rescued hybrid males, the melanogaster-derived X chromosome appeared to complete its replication faster than autosomes. These results together have been interpreted to have suggested that Lhr suppresses the lethality of hybrids by regulating functional activities of the X chromosome(s) for dosage compensation.
19 citations
TL;DR: The sex hierarchy GRN was expanded, adding novel links among genes, including a link from fruitless to Sex-lethal (Sxl) identified in both populations, and genes added in the CEGS population were enriched for genes with sex-biased splicing and components of the spliceosome.
Abstract: The Drosophila sex determination hierarchy is a classic example of a transcriptional regulatory hierarchy, with sex-specific isoforms regulating morphology and behavior. We use a structural equation modeling approach, leveraging natural genetic variation from two studies on Drosophila female head tissues – DSPR collection (596 F1-hybrids from crosses between DSPR sub-populations) and CEGS population (75 F1-hybrids from crosses between DGRP/Winters lines to a reference strain w1118) – to expand understanding of the sex hierarchy gene regulatory network (GRN). This approach is completely generalizable to any natural population, including humans. We expanded the sex hierarchy GRN adding novel links among genes, including a link from fruitless (fru) to Sex-lethal (Sxl) identified in both populations. This link is further supported by the presence of fru binding sites in the Sxl locus. 754 candidate genes were added to the pathway, including the splicing factors male-specific lethal 2 and Rm62 as downstream targets of Sxl which are well-supported links in males. Independent studies of doublesex and transformer mutants support many additions, including evidence for a link between the sex hierarchy and metabolism, via Insulin-like receptor. The genes added in the CEGS population were enriched for genes with sex-biased splicing and components of the spliceosome. A common goal of molecular biologists is to expand understanding about regulatory interactions among genes. Using natural alleles we can not only identify novel relationships, but using supervised approaches can order genes into a regulatory hierarchy. Combining these results with independent large effect mutation studies, allows clear candidates for detailed molecular follow-up to emerge.
15 citations
TL;DR: It is speculated that the presence of an additional splice form, perhaps encoding non-functional protein only in testis, may prevent the feminizing effects exerted by the functional IX protein.
Abstract: Intersex (ix), a gene required for female sexual development in Drosophila, acts in concert with doublesex (dsx) at the end of the sex determination pathway. In the present study a homologue of ix was identified in Bombyx mori. Expression analysis of this gene by RT–PCR and RNase protection assay revealed a diagnostic alternative splice form present only in testis, whereas the most common splice form was found to express in all other tissues from early embryonic developmental stages. The present study provides evidence for the presence of an alternative splice form of ix in three species of silkmoths examined. Taken together with the results of an earlier study on ix in piralid moth, Maruca vitrata (Cavaliere et al. 2009), the present study suggests that the testis-specific splice form may be a characteristic feature of lepidopterans. Though ix lacks a conserved splicing pattern it appears to have retained its functional conservation in terminal sexual differentiation. We speculate that the presence of an additional splice form, perhaps encoding non-functional protein only in testis, may prevent the feminizing effects exerted by the functional IX protein.
9 citations
Cites background from "Genetic analysis of an intersex all..."
...Another study (Acharyya and Chatterjee 2002), revealed the possible functions of ix in Drosophila males by characterizing an allele of ix (ix5)....
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TL;DR: It is suggested that loss of function of ix causes massive cell death in both male andFemale genital primordia of genital discs, resulting phenotype mimicking in male and female characteristics in genitals.
Abstract: In Drosophila melanogaster, the intersex (ix) is a terminally positioned gene in somatic sex determination hierarchy and function with the female specific product of double sex (DSX F) to implement female sexual differentiation. The null phenotype of ix is to transform diplo-X individuals into intersexes while leaving haplo-X animals unaffected. This study on the effect of different intersexmutations on genital disc development provides the following major results: (i) similar range of a characteristic array of morphological structures (from almost double sex terminalia to extreme reduction of terminal appendages) was displayed by the terminalia of XX ix 1
/ix 1, XX ix 2
/ix 2 and XX ix 5
/ix 5 individuals; (ii) an increased number of apoptotic cells were found to occur in a localized manner in mature third instar larval genital discs of ix individuals; (iii) ix mutations can induce high frequency of neoplastic tumours in genitals in the presence of decapentaplegic (dpp d
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) mutations; and (iv) heteroallelic combinations of dpp d
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mutations can also induce tumours in intersex genitals with variable expressivity. On the basis of these findings, we suggest that: (i) loss of function of ixcauses massive cell death in both male and female genital primordia of genital discs, resulting phenotype mimicking in male and female characteristics in genitals; and (ii) at the discs, the apoptotic cells persist as ‘undead’ cells that can induce oncogenic transformation in the neighbouring disc cells when dppsignalling is blocked or reduced by dpp d
i
s
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mutations.
8 citations
Dissertation•
16 Feb 2007
TL;DR: A comparative biochemical and functional characterisation of the Mediator in the two ascomycete yeasts S. cerevisiae and S. pombe to address to what degree subunit architecture and specific regulatory functions have been conserved between these two species.
Abstract: The Mediator complex is an essential multiprotein coregulator of RNA polymerase II (pol II)dependent transcription in fungi and metazoans. Mediator interacts directly with both pol II and sequence-specific transcriptional regulators and thus acting as a bridge between the two. We have performed a comparative biochemical and functional characterisation the Mediator in the two ascomycete yeasts S. cerevisiae and S. pombe to address to what degree subunit architecture and specific regulatory functions have been conserved between these two species. In Paper I we identified the Med31 protein as a stable subunit of Mediator in S. cerevisiae and S. pombe. We defined a highly conserved central motif in the Med31 protein that appeared to be required but not sufficient for the association of Med31 with the rest of the Mediator complex. In Paper II we investigated the structural basis for the global shutdown of pol IIdependent transcription in the S. cerevisiae MED17 temperature sensitive allele srb4-138. We found that the srb4-138 allele disrupts the interaction between the head and middle domains both in vitro and in vivo. This suggested that the global shutdown of transcription in srb4-138 cells at the non-permissive temperature is caused by destabilisation of the core Mediator
5 citations
References
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Book•
23 Mar 1992
TL;DR: Chromosomes: Deficiencies, Inversions, and Transposable Elements.
Abstract: Genes. Chromosomes: Deficiencies. Duplications. Inversions. Rings. Translocations. Transpositions. External Anatomy (figure). Normal Chromosome Complement. Special Chromosomes: Balancers. Compound Chromosomes. X-Y Combinations. Y Derivatives. Autosynaptic Chromosomes. Transposable Elements. Departures from Diploidy. Satellite Sequences. Nonchromosomal Inheritance. Cytogenetic Map.
3,102 citations
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TL;DR: Courtship in Drosophila is influenced by a wide variety of genes, in that many different kinds of pleiotropic mutations lead to defective courtship; the broad temporal and spatial expression of most of the fly's "neuro genes" makes it difficult to exclude elements of such genes' actions as materially underlying reproductive behavior.
Abstract: Courtship in Drosophila is influenced by a wide variety of genes, in that many different kinds of pleiotropic mutations lead to defective courtship This may seem to be a truism, but the broad temporal and spatial expression of most of the fly9s "neuro genes" makes it difficult to exclude elements of such genes9 actions as materially underlying reproductive behavior "Courtship genes" that seem to play more particular roles were originally identified as sensory, learning, or rhythm mutations; their reproductive abnormalities have been especially informative for revealing components of male or female actions that might otherwise have gone unnoticed Further behavioral mutations seemed originally to be courtship-specific, turned out not to have that property, and have led to a broadened perspective on the nature and action of Drosophila9s sex-determination genes
658 citations
"Genetic analysis of an intersex all..." refers background in this paper
...Recently, Keisman et al. (2001) noted that dsx regulates the anterior-posterior (A}P) organizer to control sex-specific patterns of growth in the genital imaginal disc of Drosophila....
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...flies’ courtship behaviour (Hall, 1994)....
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TL;DR: This review compares and contrast the strategies used for sex determination between "the fly" and "the worm" and the way this understanding has come about and striking similarities have been found in the genetic strategies used by these two species to differentiate their sexes.
Abstract: ▪ Abstract For 600 million years, the two best-understood metazoan species, the nematode Caenorhabditis elegans and the fruit fly Drosophila melanogaster, have developed independent strategies for solving a biological problem faced by essentially all metazoans: how to generate two sexes in the proper proportions. The genetic program for sexual dimorphism has been a major focus of research in these two organisms almost from the moment they were chosen for study, and it may now be the best-understood general aspect of their development. In this review, we compare and contrast the strategies used for sex determination (including dosage compensation) between “the fly” and “the worm” and the way this understanding has come about. Although no overlap has been found among the molecules used by flies and worms to achieve sex determination, striking similarities have been found in the genetic strategies used by these two species to differentiate their sexes.
567 citations
TL;DR: It is suggested that the AS-C encodes several homologous polypeptides, which represent a subset of a larger gene family, and each member of the family functions at an equivalent stage of a unique morphogenetic operation involving the segregation of individual neural lineages from the epidermal anlage.
Abstract: We have determined the nucleotide sequence of two transcription units of the AS-C and shown that their potential protein coding regions share two principal domains of homology. Both domains are conserved within the myc protein family, and one of them is highly homologous with the consensus for protein tyrosine kinase substrates. We show in addition that at least one of these domains is shared with other transcription units within the AS-C, some of which were not previously known. We suggest that the AS-C encodes several homologous polypeptides, which represent a subset of a larger gene family. We propose that each member of the family functions at an equivalent stage of a unique morphogenetic operation involving the segregation of individual neural lineages from the epidermal anlage.
453 citations
TL;DR: It is shown that the tra, tra-2 and dsx loci determine sex in a cell-autonomous manner and are major regulatory loci that control the batteries of genes necessary for the development of many, and perhaps all, secondary sexual characteristics.
Abstract: Sex determination in Drosophila melanogaster is under the control of the X chromosome:autosome ratio and at least four major regulatory genes: transformer (tra), transformer-2 (tra-2), doublesex (dsx) and intersex (ix). Attention is focused here on the roles of these four loci in sex determination. By examining the sexual phenotype of clones of homozygous mutant cells produced by mitotic recombination in flies heterozygous for a given recessive sex-determination mutant, we have shown that the tra, tra-2 and dsx loci determine sex in a cell-autonomous manner. The effect of removing the wild-type allele of each locus (by mitotic recombination) at a number of times during development has been used to determine when the wild-type alleles of the tra, tra-2 and dsx loci have been transcribed sufficiently to support normal sexual development. The wild-type alleles of all three loci are needed into the early pupal period for normal sex determination in the cells that produce the sexually dimorphic (in pigmentation) cuticle of the fifth and sixth dorsal abdominal segments. tra(+) and tra-2(+) cease being needed shortly before the termination of cell division in the abdomen, whereas dsx(+) is required at least until the end of division. By contrast, in the foreleg, the wild-type alleles of tra(+) and tra-2(+) have functioned sufficiently for normal sexual differentiation to occur by about 24 to 48 hours before pupariation, but dsx(+) is required in the foreleg at least until pupariation.--A comparison of the phenotypes produced in mutant/deficiency and homozygous mutant-bearing flies shows that dsx, tra-2 and tra mutants result in a loss of wild-type function and probably represent null alleles at these genes.-All possible homozygous doublemutant combinations of ix, tra-2 and dsx have been constructed and reveal a clear pattern of epistasis: dsx > tra, tra-2 > ix. We conclude that these genes function in a single pathway that determines sex. The data suggest that these mutants are major regulatory loci that control the batteries of genes necessary for the development of many, and perhaps all, secondary sexual characteristics.-The striking similarities between the properties of these loci and those of the homeotic loci that determine segmental and subsegmental specialization during development suggest that the basic mechanisms of regulation are the same in the two situations. The phenotypes and interactions of these sex-determination mutants provide the basis for the model of how the wild-type alleles of these loci act together to effect normal sex determination. Implications of these observations for the function of other homeotic loci are discussed.
347 citations