POSTLETHWAIT, John/H*; YAN, Yi-Lin; AMORES, Angel; CRESKO, Bill; SINGER, Amy; RUBIN, David; University of Oregon, Eugene, OR; Illinois State University, Normal, IL: Consequences of genome duplication for the evolution of developmental mechanisms in teleost fish

Genome amplification, probably as a result of genome duplication, occurred prior to two key nodes of chordate evolution: the origin of vertebrates, the most diverse group of chordates, and the radiation of the teleosts, the most species-rich group of vertebrates. After genome duplication, most duplicated genes rapidly revert to single copy, but those retained in duplicate generally come to be expressed in overlapping but distinct patterns in development, a process modeled by subfunction partitioning and the origin of novel functions. How do genetic regulatory networks evolve as duplicated genes change over time? In one hypothesis, a one-to-one relationship of members of the pathway is maintained as subfunctions partition to give two parallel pathways in different subregions of the pre-duplication expression domain. In another hypothesis, pathways evolve as networks with variable and redundant interactions. To approach that question, we are investigating the regulation of duplicated genes in the developmental pathway leading to cartilage and bone and hindbrain patterning in zebrafish and comparing results with the orthologous genes in stickleback and other teleosts. We find that the network model appears to predict better than the parallel model, and that expression patterns of orthologs differ in different teleosts. These evolutionary events after the teleost genome duplication serve as a model for similar evolutionary changes that occurred in the genome amplifications at the base of vertebrate origins.