Unlike microevolutionary processes, little is known about the genetic basis of macroevolutionary processes. One of these magnificent examples is the transition from non-avian dinosaurs to birds that has created numerous evolutionary innovations such as self-powered flight and its associated wings with flight feathers. By analysing 48 bird genomes, we identified millions of avian-specific highly conserved elements (ASHCEs) that predominantly (>99%) reside in non-coding regions. Many ASHCEs show differential histone modifications that may participate in regulation of limb development. Comparative embryonic gene expression analyses across tetrapod species suggest ASHCE-associated genes have unique roles in developing avian limbs. In particular, we demonstrate how the ASHCE driven avian-specific expression of gene Sim1 driven by ASHCE may be associated with the evolution and development of flight feathers. Together, these findings demonstrate regulatory roles of ASHCEs in the creation of avian-specific traits, and further highlight the importance of cis-regulatory rewiring during macroevolutionary changes.
Bibliographical noteFunding Information:
This project was supported by Strategic Priority Research Program of the Chinese Academy of Sciences (XDB13000000) and Lundbeckfonden grant R190-2014-2827. K.T. was supported by JSPS KAKENHI Grant (JP15H04374), grant from The Naito Foundation, and Next Generation World-Leading Researchers from the Cabinet Office, Government of Japan (LS007). R.S., S.E. and H.M. are JSPS Research Fellows (JSPS KAKENHI Grant Numbers JP14J07050 (R.S.), JP15J06859 (S.E.), JP15J06385 (H.M.)). C.L. was partially supported by Lundbeckfonden grant R52-5062 to M.T.P.G.). N.I. was partially supported by Platform Project for Supporting in Drug Discovery and Life Science Research Platform for Dynamic Approaches to Living System from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) and Japan Agency for Medical Research and Development (AMED). Photographs of the adult Cochin bantam and Brahmas bantam and their fertilized eggs were provided by the National BioResource Project (NBRP) Chicken/Quail of the MEXT, Japan