Molecular characterization and phylogenetic analysis of Wx genes of four diploid species of the Triticeae genera Eremopyrum, Psathyrostachys, and Henrardia

In wheat endosperm, the granule-bound starch synthase or the Waxy protein is the sole enzyme for amylose synthesis and thus determines the amylose content and ratio of amylose/amylopectin. The gene encoding this enzyme has been named as Waxy ( Wx ) gene. In this study, eight novel Wx alleles from four diploid species belonging to the three Triticeae genera, namely Eremopyrum , Psathyrostachys , and Henrardia have been isolated and characterized. The genetic diversity of these genes was evaluated at the molecular sequence level, and the nucleotides of these Wx genes were also compared with their homologs from wheat and its relatives. The Wx alleles of P. juncea (Fischer) Nevski, E. triticeum (Gaertn.) Nevski, E. bonaepartis (Sprengel) Nevsk, and H. persica (Boiss.) C. E. Hubbard showed obvious differences from the homologous alleles known from wheat and Aegilops as well as Taeniatherum in terms of nucleotide composition, intron length, isoelectric point, and molecular mass. Phylogenetic analysis suggested that the Wx alleles of these four species distantly related to wheat were more closely related to those of Hordeum and Secale than the other species. These Wx alleles are novel candidates with potential application in wheat breeding for modified starch properties.