Meeting Abstract
Sexually dimorphic species produce distinct male and female phenotypes from a single, shared genome, which can be achieved through sex-specific regulation of gene expression. Although sex-biased gene expression is generally predicted to increase over ontogeny as male and female phenotypes diverge, this pattern should be most pronounced in tissues that contribute to the most extreme aspects of sexual dimorphism. However, most previous characterizations of sex-biased gene expression have looked at either 1) multiple tissues at a single time point or 2) single tissues at multiple time points, thus ignoring how sex-specific development is coordinated across multiple tissues over time. In the brown anole, a lizard that exhibits extreme sexual size dimorphism, we used RNA-Seq to analyze liver, muscle, and brain transcriptomes at 1, 4, 8, and 12 months of age to simultaneously characterize sex-, age-, and tissue-specificity of gene expression. We predicted that 1) sex-biased gene expression would increase during ontogeny, 2) these ontogenetic increases in sex-biased expression would differ between tissues, and 3) growth-regulatory gene networks would be more sex-biased in liver and muscle than in brain. We found that sex-biased gene expression increased during development, but that the trajectory of this ontogenetic increase in sex-biased expression varied between tissues. We also found that sex-biased expression of growth genes increased sharply during development in the liver and muscle, but not the brain. Our results confirm that sex-biased gene expression increases throughout ontogeny, but also show that tissue-specific trajectories need to be considered when examining the relationship between sex-biased gene expression and sexual dimorphism.
