| 1. |
- Dean, Rebecca, et al.
(författare)
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Experimental Evolution of a Novel Sexually Antagonistic Allele
- 2012
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Ingår i: PLOS Genetics. - : Public Library of Science (PLoS). - 1553-7390 .- 1553-7404. ; 8:8, s. e1002917-
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Tidskriftsartikel (refereegranskat)abstract
- Evolutionary conflict permeates biological systems. In sexually reproducing organisms, sex-specific optima mean that the same allele can have sexually antagonistic expression, i.e. beneficial in one sex and detrimental in the other, a phenomenon known as intralocus sexual conflict. Intralocus sexual conflict is emerging as a potentially fundamental factor for the genetic architecture of fitness, with important consequences for evolutionary processes. However, no study to date has directly experimentally tested the evolutionary fate of a sexually antagonistic allele. Using genetic constructs to manipulate female fecundity and male mating success, we engineered a novel sexually antagonistic allele (SAA) in Drosophila melanogaster. The SAA is nearly twice as costly to females as it is beneficial to males, but the harmful effects to females are recessive and X-linked, and thus are rarely expressed when SAA occurs at low frequency. We experimentally show how the evolutionary dynamics of the novel SAA are qualitatively consistent with the predictions of population genetic models: SAA frequency decreases when common, but increases when rare, converging toward an equilibrium frequency of similar to 8%. Furthermore, we show that persistence of the SAA requires the mating advantage it provides to males: the SAA frequency declines towards extinction when the male advantage is experimentally abolished. Our results empirically demonstrate the dynamics underlying the evolutionary fate of a sexually antagonistic allele, validating a central assumption of intralocus sexual conflict theory: that variation in fitness-related traits within populations can be maintained via sex-linked sexually antagonistic loci.
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| 2. |
- Frings, Oliver, et al.
(författare)
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Network Analysis of Functional Genomics Data : Application to Avian Sex-Biased Gene Expression
- 2012
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Ingår i: Scientific World Journal. - : Hindawi Limited. - 1537-744X. ; , s. 130491-
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Tidskriftsartikel (refereegranskat)abstract
- Gene expression analysis is often used to investigate the molecular and functional underpinnings of a phenotype. However, differential expression of individual genes is limited in that it does not consider how the genes interact with each other in networks. To address this shortcoming we propose a number of network-based analyses that give additional functional insights into the studied process. These were applied to a dataset of sex-specific gene expression in the chicken gonad and brain at different developmental stages. We first constructed a global chicken interaction network. Combining the network with the expression data showed that most sex-biased genes tend to have lower network connectivity, that is, act within local network environments, although some interesting exceptions were found. Genes of the same sex bias were generally more strongly connected with each other than expected. We further studied the fates of duplicated sex-biased genes and found that there is a significant trend to keep the same pattern of sex bias after duplication. We also identified sex-biased modules in the network, which reveal pathways or complexes involved in sex-specific processes. Altogether, this work integrates evolutionary genomics with systems biology in a novel way, offering new insights into the modular nature of sex-biased genes.
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| 3. |
- Mank, Judith E, et al.
(författare)
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Faster-Z evolution is predominantly due to genetic drift.
- 2010
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Ingår i: Molecular biology and evolution. - 0737-4038 .- 1537-1719. ; 27:3, s. 661-670
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Tidskriftsartikel (refereegranskat)abstract
- Genes linked to sex chromosomes may show different levels of functional change than autosomal genes due to different evolutionary pressures. We used whole-genome data from zebra finch-chicken orthologs to test for Faster-Z evolution, finding that Z-linked genes evolve up to 50% more rapidly than autosomal genes. We combined these divergence data with information about sex-specific expression patterns in order to determine whether the Faster-Z Effect that we observe was predominantly the result of positive selection of recessive beneficial mutations in the heterogametic sex or primarily due to genetic drift attributable to the lower effective population size of the Z chromosome compared with an autosome. The Faster-Z Effect was no more prevalent for genes expressed predominantly in females; therefore, our data indicate that the largest source of Faster-Z Evolution is the increased levels of genetic drift on the Z chromosome. This is likely a product of sexual selection acting on males, which reduces the effective population size of the Z relative to that of the autosomes. Additionally, this latter result suggests that the relative evolutionary pressures underlying Faster-Z Evolution are different from those in analogous Faster-X Evolution.
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| 4. |
- Mank, Judith E., et al.
(författare)
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Ontogenetic Complexity of Sexual Dimorphism and Sex-Specific Selection
- 2010
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Ingår i: Molecular biology and evolution. - : Oxford University Press (OUP). - 0737-4038 .- 1537-1719. ; 27:7, s. 1570-1578
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Tidskriftsartikel (refereegranskat)abstract
- Sex-biased gene expression is becoming an increasingly important way to study sexual selection at the molecular genetic level. However, little is known about the timing, persistence, and continuity of gene expression required in the creation of distinct male and female phenotypes, and even less about how sex-specific selection pressures shift over the life cycle. Here, we present a time-series global transcription profile for autosomal genes in male and female chicken, beginning with embryonic development and spanning to reproductive maturity, for the gonad. Overall, the amount and magnitude of sex-biased expression increased as a function of age, though sex-biased gene expression was surprisingly ephemeral, with very few genes exhibiting continuous sex bias in both embryonic and adult tissues. Despite a large predicted role of the sex chromosomes in sexual dimorphism, our study indicates that the autosomes house the majority of genes with sex-biased expression. Most interestingly, sex-specific evolutionary pressures shifted over the course of the life cycle, acting equally strongly on female-biased genes and male-biased genes but at different ages. Female-biased genes exhibited high rates of divergence late in embryonic development, shortly before arrested meiosis halts oogenesis. The level of divergence on female-biased late embryonic genes is similar to that seen in male-biased genes expressed in adult gonads, which correlates with the onset of spermatogenesis. These analyses reveal that sex-specific selection pressure varies over the life cycle as a function of male and female biology.
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