THE Y CHROMOSOMES OF DROSOPHILA SIMULANS ARE HIGHLY POLYMORPHIC FOR THEIR ABILITY TO SUPPRESS SEX-RATIO DRIVE

Abstract The X and Y chromosomes of Drosophila melanogaster each contain a cluster of several hundred ribosomal RNA genes (rDNA). A nontranscribed spacer region separates adjacent rRNA genes and contains tandem copies of 240 bp repeats that include the initiation site for RNA polymerase I transcription. We show here that Drosophila simulans, a sibling species of D. melanogaster, contains few, if any, rRNA genes on its Y chromosome but carries instead a large block (3,000 kb or 12,500 copies) of 240 bp nontranscribed spacer repeats. The repeats are located at the tip of the long arm of the simulans Y chromosome, in contrast to their location among rRNA genes on the short arm of the Y chromosome of D. melanogaster. The bobbed mutation in homozygous females of D. melanogaster shortens and thins the bristles, owing to a partial deletion of rRNA genes on the X chromosome. The bristles of bobbed/Y males are normal owing to the presence of a full complement of rRNA genes on the Y chromosome. Peculiarly, in bobbed/Y males of D. simulans the short bristle phenotype does not return to normal but is enhanced by the presence of the Y chromosome. We propose that the 12,500 nontranscribed spacer repeats on the Y chromosome are responsible for this biological effect by competition for a protein factor(s) essential for normal levels of rDNA transcription at the X-linked locus.

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Sex-ratio meiotic drive in Drosophila simulans: cellular mechanism, candidate genes and evolution

Biochemical Society Transactions ◽

10.1042/bst0340562 ◽

2006 ◽

Vol 34 (4) ◽

pp. 562-565 ◽

Cited By ~ 13

Author(s):

C. Montchamp-Moreau

Keyword(s):

Sex Ratio ◽

X Chromosome ◽

Natural Populations ◽

Meiotic Drive ◽

Female Offspring ◽

Drosophila Simulans ◽

X Chromosomes ◽

Individual Fitness ◽

Primary Sex Ratio ◽

Intragenomic Conflict

The sex-ratio trait, reported in a dozen Drosophila species, is a type of naturally occurring meiotic drive in which the driving elements are located on the X chromosome. Typically, as the result of a shortage of Y-bearing spermatozoa, males carrying a sex-ratio X chromosome produce a large excess of female offspring. The presence of sex-ratio chromosomes in a species can have considerable evolutionary consequences, because they can affect individual fitness and trigger extended intragenomic conflict. Here, I present the main results of the study performed in Drosophila simulans. In this species, the loss of Y-bearing spermatozoa is related to the inability of the Y chromosome sister-chromatids to separate properly during meiosis II. Fine genetic mapping has shown that the primary sex-ratio locus on the X chromosome contains two distorter elements acting synergistically, both of which are required for drive expression. One element has been genetically mapped to a tandem duplication. To infer the natural history of the trait, the pattern of DNA sequence polymorphism in the surrounding chromosomal region is being analysed in natural populations of D. simulans harbouring sex-ratio X chromosomes. Initial results have revealed the recent spread of a distorter allele.

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The Sex-Ratio Trait in Drosophila simulans: Geographical Distribution of Distortion and Resistance

Evolution ◽

10.2307/2411010 ◽

1997 ◽

Vol 51 (6) ◽

pp. 1886 ◽

Cited By ~ 32

Author(s):

Anne Atlan ◽

Herve Mercot ◽

Claudie Landre ◽

Catherine Montchamp-Moreau

Keyword(s):

Sex Ratio ◽

Geographical Distribution ◽

Drosophila Simulans

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Sex ratio distortion in bovine sperm correlates to recombination in the pseudoautosomal region

Genetics Research ◽

10.1017/s0016672399004085 ◽

2000 ◽

Vol 75 (1) ◽

pp. 53-59 ◽

Cited By ~ 11

Author(s):

JOANNA SZYDA ◽

HENNER SIMIANER ◽

SIGBJØRN LIEN

Keyword(s):

Sex Ratio ◽

Recombination Rate ◽

Regression Models ◽

Segregation Ratio ◽

Pseudoautosomal Region ◽

Logistic Regression Models ◽

Bovine Sperm ◽

Y Chromosomes ◽

Ratio Distortion ◽

Sex Ratio Distortion

A total of 2122 single sperm from 35 bulls belonging to six different paternal half-sib groups were analysed with respect to two markers in the bovine pseudoautosomal region (PAR) and sex- specific loci on the X and Y chromosomes, respectively. A segregation ratio significantly different from 1[ratio ]1 was observed in a test over all families, with a higher proportion of X-bearing gametes (53·5%). The analysis of recombination conducted separately for X- and Y-bearing sperm showed that X-bearing sperm cells possess highly significant individual and between-family variability in recombination rate, whereas Y-bearing sperm show linkage homogeneity. To test whether the two phenomena are related, different logistic regression models were fitted to the data. The results show that sex ratio significantly correlates with changes in recombination rate among X-bearing but not among Y-bearing sperm. Different hypotheses to explain these observations are discussed.

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Seed sexing revealed female bias in two Rumex species

Acta Societatis Botanicorum Poloniae ◽

10.5586/asbp.2011.028 ◽

2011 ◽

Vol 80 (2) ◽

pp. 93-97 ◽

Cited By ~ 2

Author(s):

Dagmara Kwolek ◽

Andrzej J. Joachimiak

Keyword(s):

Sex Ratio ◽

Sex Chromosomes ◽

Dna Markers ◽

Sex Chromosome ◽

Sex Ratios ◽

Ratio Bias ◽

Sex Ratio Bias ◽

Y Chromosomes ◽

Sex Chromosome System ◽

Female Bias

Sex-ratio bias in seeds of dioecious Rumex species with sex chromosomes is an interesting and still unsettled issue. To resolve gender among seeds of R. acetosa and R. thyrsiflorus (two species with an XX/XY1Y2 sex chromosome system), this work applied a PCR-based method involving DNA markers located on Y chromosomes. Both species showed female-biased primary sex ratios, with female bias greater in R. acetosa than in R. thyrsiflorus. The observed predominance of female seeds is consistent with the view that the female biased sex ratios in Rumex are conditioned not only postzygotically but also prezygotically.

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Natural variation of the Y chromosome suppresses sex ratio distortion and modulates testis-specific gene expression in Drosophila simulans

Heredity ◽

10.1038/hdy.2013.5 ◽

2013 ◽

Vol 111 (1) ◽

pp. 8-15 ◽

Cited By ~ 18

Author(s):

A T Branco ◽

Y Tao ◽

D L Hartl ◽

B Lemos

Keyword(s):

Gene Expression ◽

Sex Ratio ◽

Y Chromosome ◽

Natural Variation ◽

Drosophila Simulans ◽

Specific Gene ◽

Specific Gene Expression ◽

Ratio Distortion ◽

Sex Ratio Distortion

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Selective Sweeps in a 2-Locus Model for Sex-Ratio Meiotic Drive in Drosophila simulans

Molecular Biology and Evolution ◽

10.1093/molbev/msm269 ◽

2007 ◽

Vol 25 (2) ◽

pp. 409-416 ◽

Cited By ~ 16

Author(s):

Nicolas Derome ◽

Emmanuelle Baudry ◽

David Ogereau ◽

Michel Veuille ◽

Catherine Montchamp-Moreau

Keyword(s):

Sex Ratio ◽

Meiotic Drive ◽

Drosophila Simulans ◽

Selective Sweeps ◽

Locus Model

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Hybrid lethal systems in the Drosophila melanogaster species complex. I. The maternal hybrid rescue (mhr) gene of Drosophila simulans.

Genetics ◽

10.1093/genetics/133.2.299 ◽

1993 ◽

Vol 133 (2) ◽

pp. 299-305 ◽

Cited By ~ 4

Author(s):

K Sawamura ◽

T Taira ◽

T K Watanabe

Keyword(s):

Drosophila Melanogaster ◽

Complex I ◽

Species Complex ◽

Reciprocal Cross ◽

Drosophila Simulans ◽

Hybrid Male ◽

Larval Stages ◽

Embryonic Lethal ◽

Y Chromosomes ◽

Lethal Hybrid

Abstract Hybrid females from Drosophila simulans females x Drosophila melanogaster males die as embryos while hybrid males from the reciprocal cross die as late larvae. The other two classes are sterile adults. Letting C, X, and Y designate egg cytoplasm, X, and Y chromosomes, respectively, and subscripts m and s stand for melanogaster and simulans, CmXmYs males are lethal in the larval stage and are rescued by the previously reported genes, Lhr (Lethal hybrid rescue) in simulans or Hmr (Hybrid male rescue) in melanogaster. We report here another rescue gene located on the second chromosome of simulans, mhr (maternal hybrid rescue) that, when present in the mother, rescues CsXmXs females from embryonic lethality. It has been postulated that the hybrids not carrying the Xs like CmXmYs males are larval lethal and that the hybrids carrying both the Cs and the Xm like CsXmXs females are embryonic lethal. According to these postulates CsXmYs males (obtained by mating attached-X simulans females to melanogaster males) should be doubly lethal, at both embryo and larval stages. When both rescuing genes are present, Hmr in the father and mhr in the mother, males of this genotype are fully viable, as predicted.

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