Meeting Abstract

109.6  Tuesday, Jan. 7 09:15  Molecular evolution and expression of feather structural proteins, alpha and beta keratins, in birds GREENWOLD, MJ*; BAO, W; SAWYER, RH; University of South Carolina greenwold@biol.sc.edu

Feathers are one of the most distinguishing features of birds and feather diversity is directly related to sexual selection and ecological niches. Today’s feathers are composed of two types of fibrous, structural proteins, alpha and beta keratins. While, alpha-keratins are found in all vertebrates, beta-keratins are found exclusively in reptiles and birds. Alpha keratins are separated into two types, Type I or acidic alpha-keratins and Type II or neutral/basic alpha-keratins and avian beta-keratins are divided into 4 subfamilies (feather, scale, claw and keratinocyte beta-keratins). This study details the expansion and contraction of these gene families in birds using the genomes of 48 phylogenetically diverse birds. In birds, we found that the mean number of alpha-keratins is significantly lower than in reptiles and mammals and that at least 14 “epithelial” or “hair” alpha-keratins have been lost in the avian lineage. Additionally, we find that the avian specific feather beta-keratins comprise a large majority of each species’ total number of beta-keratins and that aquatic and semi-aquatic birds have a proportionally smaller number of feather beta-keratins and a larger proportion of keratinocyte beta-keratins than terrestrial birds. Comparative transcriptome analysis of the scutate scale, dorsal and wing feather during embryonic development identifies 26 of the 27 alpha-keratins and at least 102 beta-keratins are differentially expressed in the chicken. These data indicate that the expansion of beta-keratins and contraction of alpha-keratins in the stem lineage of birds likely shaped the early evolution of feathers and subsequent alpha and beta-keratin gene family dynamics continued to shape the evolution of feathers in birds.