Abstracts (first author)

Talk 

Short- and long-term evolution of gene expression and sequence divergence on the avian Z chromosome

Author(s): Wright AE, Harrison PW, Pointer MA, Mank JE

Summary:

Sex chromosomes provide unique opportunities to study the fundamental evolutionary forces that act on the entirety of the genome. Because of their unusual pattern of transmission, biological differences between males and females cause sex chromosomes to experience distinct evolutionary environments, which in turn influence coding sequence, gene expression, and even splice forms. The avian Z chromosome is separated into multiple distinct strata, formed by numerous recombination suppression events that have evolved independently across different avian lineages. This provides a unique opportunity to examine the effects of sex-specific selection on the same chromosome across evolutionary time scales.

We first mapped out the fine-scale evolutionary history of the Z chromosome across a clade of birds, encompassing roughly 80 million years. Our results show that replicate strata have formed independently across this clade. We then used multiple integrated next-generation datasets to measure gene expression and gene sequence divergence across four species within this clade that experience different sex-specific selection regimes. Our data indicate that male-biased gene expression accumulates over time across Z chromosome strata, with older strata showing greater levels of male-bias. This is consistent with the fact that Z-linked genes are more often selected for male-specific effects. We also show that sex chromosome divergence influences sex-specific alternative splicing, leading to the loss of female-specific exons from the Z chromosome.


Video


Abstracts (coauthor)

Summary:

We assembled de novo transcriptomes for six species within the Galloanserae (fowl and waterfowl) in order to assess the link between complex phenotypic sexual dimorphism and global gene expression differences between males and females. The six species exhibit the full range of sexual dimorphism, from monomorphism observed in geese to extreme sexual dimorphism in peafowl. This gradient of sexual dimorphism within a single clade makes it possible to directly test how sexual selection affects genome evolution and how sexually dimorphic phenotypes are encoded. To do this, we generated an extensive RNA-Seq dataset, with on average 95 Gb of next-generation Illumina sequencing data for each species, sampling both male and female spleen and gonad tissue. After constructing de novo transcriptome assemblies for each species using Trinity and establishing orthology across all six study species, we assessed sex-specific gene expression and sequence evolution of sex-biased genes in order build a comprehensive picture of the role of mating system in genome evolution.

The generated de novo transcriptomes for each species contain on average 15,847 significantly expressed contig groups, which resulted in 12,337 predicted peptides on average per species, from which orthology was inferred across the clade. Our results indicate that transcriptional masculinization and feminization are correlated with the overall degree of sexual dimorphism in phenotype, and that sex-specific selection shapes coding sequence evolution of sex-biased genes.

Contacts

Chairman: Octávio S. Paulo
Tel: 00 351 217500614 direct
Tel: 00 351 217500000 ext22359
Fax: 00 351 217500028
email: mail@eseb2013.com

Address

XIV Congress of the European Society for Evolutionary Biology

Organization Team
Department of Animal Biology (DBA)
Faculty of Sciences of the University of Lisbon
P-1749-016 Lisbon
Portugal

Website

Computational Biology & Population Genomics Group 
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