Implication of Estrogen Response Elements in Expression of Secondary Sex-Traits in the Sex-Role Reversed Gulf Pipefish, Syngnathus scovelli

Abstract

Intralocus conflict, the differential selection optima for a genomic region, between males and females created by sexual selection can be resolved with the presence of sex-biased hormone response elements (HREs) in the genome which allow for gene regulation through sex-biased hormones. In general, cis-regulatory elements are found more frequently and in closer proximity to hormonally responsive genes. I predict that genes putatively under sexual selection are more likely to have a greater number of proximal sex-biased HREs than randomly selected genes. To investigate this I chose to use estrogen response elements (EREs) and the sex-role reversed Gulf pipefish, Syngnathus scovelli. I demonstrate the secondary sex traits, transverse bands, and body depth described in female S. scovelli do not have any confounding effects of age and confirm those traits do affect male mate choice. To scan the genome of S. scovelli for EREs, I developed and tested an algorithm for identifying putative estrogen binding regions. With confirmation of the secondary sex traits putatively under sexual selection, I used feminized males with female traits to elucidate genes that are involved in production of body depth and ornamentation (i.e., transverse bands). I was able to show that these genes have an excess of EREs compared to typically sex-differentiated genes thereby demonstrating the important role EREs can play in sexual selection.