scholarly journals The microevolutionary response to male-limited X-chromosome evolution in Drosophila melanogaster reflects macroevolutionary patterns

2019 ◽  
Author(s):  
Jessica K. Abbott ◽  
Adam K. Chippindale ◽  
Edward H. Morrow
Keyword(s):  
Genetic Variation ◽  
Sexual Dimorphism ◽  
X Chromosome ◽  
Experimental Evolution ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Direct Effects ◽  
Metabolic Genes ◽  
X Chromosome Evolution ◽  
Trans Regulation

AbstractDue to its hemizygous inheritance and role in sex determination, the X chromosome is expected to play an important role in the evolution of sexual dimorphism, and to be enriched for sexually antagonistic genetic variation. By forcing the X chromosome to only be expressed in males over >40 generations, we changed the selection pressures on the X to become similar to those experienced by the Y. This releases the X from any constraints arising from selection in females, and should lead to specialization for male fitness, which could occur either via direct effects of X-linked loci or trans-regulation of autosomal loci by the X. We found evidence of masculinization via upregulation of male-benefit sexually antagonistic genes, and downregulation of X-linked female benefit genes. Interestingly, we could detect evidence of microevolutionary changes consistent with previously documented macroevolutionary patterns, such as changes in expression consistent with previously established patterns of sexual dimorphism, an increase in the expression of metabolic genes related to mitonuclear conflict, and evidence that dosage compensation effects can be rapidly altered. These results confirm the importance of the X in the evolution of sexual dimorphism and as a source for sexually antagonistic genetic variation, and demonstrate that experimental evolution can be a fruitful method for testing theories of sex chromosome evolution.

scholarly journals Feminisation of complex traits in Drosophila melanogaster via female-limited X chromosome evolution

2020 ◽  
Author(s):  
Katrine K. Lund-Hansen ◽  
Jessica K. Abbott ◽  
Edward H. Morrow
Keyword(s):  
Genetic Variation ◽  
Body Size ◽  
X Chromosome ◽  
Complex Traits ◽  
Development Time ◽  
Chromosome Evolution ◽  
Reproductive Fitness ◽  
Male Genome ◽  
X Chromosome Evolution ◽  
Locomotion Activity

AbstractA handful of studies have investigated sexually antagonistic constraints on obtaining sex-specific fitness optima, though exclusively through male-genome-limited evolution experiments. In this paper, we established a female-limited X chromosome evolution experiment, where we used an X chromosome balancer to enforce the inheritance of the X chromosome through the matriline, thus removing exposure to male selective constraints. This approach eliminates the effects of sexually antagonistic selection on the X chromosome, permitting evolution towards a single sex-specific optimum. After multiple generations of selection, we found strong evidence that body size and development time had moved towards a female-specific optimum, whereas reproductive fitness and locomotion activity remained unchanged. The changes in body size and development time are consistent with previous results, and suggest that the X chromosome is enriched for sexually antagonistic genetic variation controlling these traits. The lack of change in reproductive fitness and locomotion activity could be due to a number of mutually non-exclusive explanations, including a lack of sexually antagonistic variance on the X chromosome or confounding effects of the use of the balancer chromosome. This study is the first to employ female-genome-limited selection and adds to the understanding of the complexity of sexually antagonistic genetic variation.

Marsupial Cytogenetics

1989 ◽  
Vol 37 (3) ◽  
pp. 331 ◽  
Author(s):  
DL Hayman
Keyword(s):  
X Chromosome ◽  
Dna Sequences ◽  
Chromosome Numbers ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Repeated Dna ◽  
Chromosome X ◽  
X Chromosomes ◽  
Repeated Dna Sequences ◽  
Chromosome Mosaicism

This review includes a list of the chromosome numbers of marsupials and a summary of the main features of chromosome evolution in this group of mammals. Special topics discussed include sex chromosome mosaicism, the size of the marsupial X chromosome, X chromosomes and nucleolar organisers, complex sex chromosome systems, repeated DNA sequences and aspects of meiosis.

scholarly journals YY males of the dioecious plant Mercurialis annua are fully viable but produce largely infertile pollen

2019 ◽  
Author(s):  
Xinji Li ◽  
Paris Veltsos ◽  
Guillaume Cossard ◽  
Jörn Gerchen ◽  
John R. Pannell
Keyword(s):  
X Chromosome ◽  
Male Fertility ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Sequence Divergence ◽  
Sex Chromosome Evolution ◽  
Dioecious Plant ◽  
Significant Difference ◽  
Heterogametic Sex ◽  
Mercurialis Annua

SummaryThe suppression of recombination during sex-chromosome evolution is thought to be favoured by linkage between the sex-determining locus and sexually-antagonistic loci, and leads to the degeneration of the chromosome restricted to the heterogametic sex. Despite substantial evidence for genetic degeneration at the sequence level, the phenotypic effects of the earliest stages of sex-chromosome evolution are poorly known. Here, we compare the morphology, viability and fertility between XY and YY individuals produced by crossing seed-producing males in the dioecious plant Mercurialis annua L., which has young sex chromosomes with limited X-Y sequence divergence. We found no significant difference in viability or vegetative morphology between XY and YY males. However, electron microscopy revealed clear differences in pollen anatomy, and YY males were significantly poorer sires in competition with their XY counterparts. Our study suggests either that the X chromosome is required for full male fertility in M. annua, or that male fertility is sensitive to the dosage of relevant Y-linked genes. We discuss the possibility that the maintenance of male-fertility genes on the X chromosome might have been favoured in recent population expansions, which selected for the ability of females to produce pollen in the absence of males.

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