title: Evolutionary dynamics of Waxy and the origin of hexaploid Spartina species (Poaceae).
abstract: We investigated the evolutionary dynamics of duplicated copies of the granule-bound starch synthase I gene (GBSSI or Waxy) within polyploid Spartina species. Molecular cloning, sequencing, and phylogenetic analyses revealed incongruences between the expected species phylogeny and the inferred gene trees. Some genes within species were more divergent than expected from ploidy level alone, suggesting the existence of paralogous sets of Waxy loci in Spartina. Phylogenetic analyses indicate that this paralogy originated from a duplication that occurred prior to the divergence of Spartina from other Chloridoideae. Gene tree topologies revealed three divergent homoeologous sequences in the hexaploid S. alterniflora that are consistent with the proposal of an allopolyploid origin of the hexaploid clade. Waxy sequences differ in insertion-deletion events in introns, which may be used to diagnose gene copies. Both paralogous and homoeologous coding regions appear to evolving under selective constraints.
authors.affiliation: Genome Evolution and Speciation Laboratory, UMR CNRS 6553 Ecobio, University of Rennes 1, Bât 14A, Campus Scientifique de Beaulieu, Rennes Cedex, France.
authors.forename: P M
authors.initials: PM
authors.lastname: Fortune
authors.forename: K A
authors.initials: KA
authors.lastname: Schierenbeck
authors.forename: A K
authors.initials: AK
authors.lastname: Ainouche
authors.forename: J
authors.initials: J
authors.lastname: Jacquemin
authors.forename: J F
authors.initials: JF
authors.lastname: Wendel
authors.forename: M L
authors.initials: ML
authors.lastname: Ainouche
mesh_terms: D001483:Base Sequence; D019143:Evolution, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics*; D006109:Poaceae / Q000145:classification / Q000235:genetics*; D011123:Polyploidy; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D013214:Starch Synthase / Q000235:genetics*
chemical_list: D010940:Plant Proteins; C060756:waxy protein, plant; D013214:Starch Synthase