title: Evolution of VRN2/Ghd7-Like Genes in Vernalization-Mediated Repression of Grass Flowering.
abstract: Flowering of many plant species is coordinated with seasonal environmental cues such as temperature and photoperiod. Vernalization provides competence to flower after prolonged cold exposure, and a vernalization requirement prevents flowering from occurring prior to winter. In winter wheat (Triticum aestivum) and barley (Hordeum vulgare), three genes VRN1, VRN2, and FT form a regulatory loop that regulates the initiation of flowering. Prior to cold exposure, VRN2 represses FT. During cold, VRN1 expression increases, resulting in the repression of VRN2, which in turn allows activation of FT during long days to induce flowering. Here, we test whether the circuitry of this regulatory loop is conserved across Pooideae, consistent with their niche transition from the tropics to the temperate zone. Our phylogenetic analyses of VRN2-like genes reveal a duplication event occurred before the diversification of the grasses that gave rise to a CO9 and VRN2/Ghd7 clade and support orthology between wheat/barley VRN2 and rice (Oryza sativa) Ghd7 Our Brachypodium distachyon VRN1 and VRN2 knockdown and overexpression experiments demonstrate functional conservation of grass VRN1 and VRN2 in the promotion and repression of flowering, respectively. However, expression analyses in a range of pooids demonstrate that the cold repression of VRN2 is unique to core Pooideae such as wheat and barley. Furthermore, VRN1 knockdown in B. distachyon demonstrates that the VRN1-mediated suppression of VRN2 is not conserved. Thus, the VRN1-VRN2 feature of the regulatory loop appears to have evolved late in the diversification of temperate grasses.
authors: Laboratory of Genetics, U.S. Department of Energy Great Lakes Bioenergy Research Center (D.P.W., R.M.A.), and Department of Biochemistry (D.P.W., Y.D., R.M.A.), University of Wisconsin, Madison, Wisconsin 53706;Department of Plant Biology, University of Vermont, Burlington, Vermont 05405 (M.A.M., J.C.P.); andCollege of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, People's Republic of China (Y.D.).
authors: Daniel P
authors: 0000-0002-1498-5707
authors: DP
authors: Woods
authors: Laboratory of Genetics, U.S. Department of Energy Great Lakes Bioenergy Research Center (D.P.W., R.M.A.), and Department of Biochemistry (D.P.W., Y.D., R.M.A.), University of Wisconsin, Madison, Wisconsin 53706;Department of Plant Biology, University of Vermont, Burlington, Vermont 05405 (M.A.M., J.C.P.); andCollege of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, People's Republic of China (Y.D.).
authors: Meghan A
authors: MA
authors: McKeown
authors: Laboratory of Genetics, U.S. Department of Energy Great Lakes Bioenergy Research Center (D.P.W., R.M.A.), and Department of Biochemistry (D.P.W., Y.D., R.M.A.), University of Wisconsin, Madison, Wisconsin 53706;Department of Plant Biology, University of Vermont, Burlington, Vermont 05405 (M.A.M., J.C.P.); andCollege of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, People's Republic of China (Y.D.).
authors: Yinxin
authors: 0000-0002-0187-4135
authors: Y
authors: Dong
authors: Laboratory of Genetics, U.S. Department of Energy Great Lakes Bioenergy Research Center (D.P.W., R.M.A.), and Department of Biochemistry (D.P.W., Y.D., R.M.A.), University of Wisconsin, Madison, Wisconsin 53706;Department of Plant Biology, University of Vermont, Burlington, Vermont 05405 (M.A.M., J.C.P.); andCollege of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, People's Republic of China (Y.D.).
authors: Jill C
authors: 0000-0002-9211-5061
authors: JC
authors: Preston
authors: Laboratory of Genetics, U.S. Department of Energy Great Lakes Bioenergy Research Center (D.P.W., R.M.A.), and Department of Biochemistry (D.P.W., Y.D., R.M.A.), University of Wisconsin, Madison, Wisconsin 53706;Department of Plant Biology, University of Vermont, Burlington, Vermont 05405 (M.A.M., J.C.P.); andCollege of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, People's Republic of China (Y.D.) amasino@biochem.wisc.edu.
authors: Richard M
authors: 0000-0003-3068-5402
authors: RM
authors: Amasino
mesh_terms: D001499:Bayes Theorem; D058431:Brachypodium / Q000235:genetics* / Q000502:physiology*; D003080:Cold Temperature; D019143:Evolution, Molecular; D035264:Flowers / Q000235:genetics* / Q000502:physiology*; D020440:Gene Duplication; D018506:Gene Expression Regulation, Plant; D055785:Gene Knockdown Techniques; D017343:Genes, Plant; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D010940:Plant Proteins