Meeting Abstract

28.2  Wednesday, Jan. 4  Characterization and expression profiles of beta (β)-keratins in the American alligator (Alligator mississippiensis) and their molecular evolution in archosaurians GREENWOLD, MJ*; SAWYER, RH; Univ. of South Carolina, Columbia; Univ. of South Carolina, Columbia greenwold@biol.sc.edu

Extant archosaurians are comprised of crocodilians and birds. Epidermal appendages of archosaurians, including scales, claws, and feathers, are largely composed of beta (β)-keratins. In birds, β-keratins form a multigene family that can be divided into distinct subfamilies (scale, claw, feather-like, feather and keratinocyte β-keratins) based on expression profiles of epidermal appendages. While all β-keratins contain a well conserved central filament domain, the avian β-keratin subfamilies show the highest amount of diversity in the C-terminus. Previous studies on crocodilians have isolated five unique β-keratin transcripts from three crocodilian species (Crocodylus niloticus, Crocodylus palustris, Crocodylus intermedius), but these transcripts demonstrate little diversity, especially in the C-terminus. Searches of preliminary genome builds of the saltwater crocodile (Crocodylus porosus) and American alligator (Alligator mississippiensis) show a much greater amount of β-keratin diversity than previously reported. Phylogenetic analyses demonstrate that 1:1 orthologous relationships exist between crocodilian β-keratins and basal avian β-keratins. Using specific primers to β-keratins of the American alligator, we utilize real-time quantitative PCR (qPCR) to compare the relative expression of β-keratins in different tissues of the alligator embryo. Results from qPCR demonstrate that the β-keratins of the American alligator are variably expressed in different embryonic tissues. Our results indicate that basal β-keratins in present day birds are more closely related to β-keratins in crocodilians than to the avian specific feather β-keratins that form the feathers in today’s birds.