multiple mechanisms promote the retained expression of gene duplicates in the tetraploid frog xenopus laevis多种机制促进四倍体的保留的表达基因重复青蛙非洲爪蟾蜍光滑的.pdfVIP

Multiple Mechanisms Promote the Retained Expression of Gene Duplicates in the Tetraploid Frog Xenopus laevis ´ ´ [ [* Frederic J. J. Chain , Ben J. Evans Center for Environmental Genomics, Department of Biology, McMaster University, Hamilton, Ontario, Canada Gene duplication provides a window of opportunity for biological variants to persist under the protection of a co- expressed copy with similar or redundant function. Duplication catalyzes innovation (neofunctionalization), subfunction degeneration (subfunctionalization), and genetic buffering (redundancy), and the genetic survival of each paralog is triggered by mechanisms that add, compromise, or do not alter protein function. We tested the applicability of three types of mechanisms for promoting the retained expression of duplicated genes in 290 expressed paralogs of the tetraploid clawed frog, Xenopus laevis . Tests were based on explicit expectations concerning the ka/ks ratio, and the number and location of nonsynonymous substitutions after duplication. Functional constraints on the majority of paralogs are not significantly different from a singleton ortholog. However, we recover strong support that some of them have an asymmetric rate of nonsynonymous substitution: 6% match predictions of the neo- functionalization hypothesis in that (1) each paralog accumulated nonsynonymous substitutions at a significantly different rate and (2) the one that evolves faster has a higher ka/ks ratio than the other paralog and than a singleton ortholog. Fewer paralogs (3%) exhibit a complementary pattern of substitution at the protein level that is predicted by enhancement or degradation of different functional domains, and the remaining 13% have a higher average ka/ks ratio in both paralogs that is consist