title: Adaptive evolution in the GAF domain of phytochromes in gymnosperms.
abstract: The GAF domain of phytochrome is essential for photoconversion and signal transduction. In gymnosperms, it exists in all members of the phytochrome family that experience gene duplication. Maximum-likelihood models of codon substitution can provide a framework for constructing likelihood ratio tests of changes in selective pressure and make clear predictions about patterns of genetic change following gene duplication. In this study, 68 gymnosperm GAF sequences were analyzed to identify lineages and sites under positive selection. Our results indicate that (1) positive selection at a few sites (3.6%), rather than relaxation of selective constraints, has played a major role in the evolution of the gymnosperm GAF domain; (2) strong positive selective pressure tends to occur in the recent PHYP lineages of cogeneric species, but is absent in old lineages consisting of distantly related species; and (3) the selective pressure indicated by the omega ratio varies greatly among lineages and sites in the GAF domain.
authors.affiliation: Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, Hubei, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.forename: Boqian
authors.initials: B
authors.lastname: Yan
authors.forename: Guopei
authors.initials: G
authors.lastname: Chen
authors.forename: Yingjuan
authors.initials: Y
authors.lastname: Su
authors.forename: Ting
authors.initials: T
authors.lastname: Wang
mesh_terms: D000220:Adaptation, Biological / Q000235:genetics*; D032462:Cycadopsida / Q000235:genetics*; D019143:Evolution, Molecular; D049810:Genetic Speciation; D014644:Genetic Variation / Q000502:physiology; D005810:Multigene Family / Q000235:genetics; D010802:Phylogeny; D010834:Phytochrome / Q000737:chemistry* / Q000235:genetics*; D017434:Protein Structure, Tertiary / Q000235:genetics; D012641:Selection, Genetic
chemical_list: D010834:Phytochrome