Characterization and Phylogenetic Analysis of the Genes Coding for High Molecular Weight Glutenin Subunits in Three Diploid Species of Aegilops

This work reports the molecular characterization of high molecular weight (HMW) glutenin subunits belonging to the diploid species Aegilops comosa, Aegilops uniaristata, and Aegilops speltoides, which represent three important genomes of the genus Aegilops: M, Un, and S, respectively. Besides improving our knowledge of Aegilops glutenins, which is useful in wheat breeding programs, this study examines the phylogenetic relationships between the glutenin genes of an important group of species of the tribe Triticeae. The new glutenin proteins examined (coded by Glu-Mx, Glu-My, Glu-Unx, Glu-Uny, and Glu-Sy) showed the same general characteristics as those previously described in other species of the tribe Triticeae. A phylogenetic study of the relationships between the new members of the Glu gene family and other known sequences of glutenin genes of the genera Aegilops, Triticum, and Secale was performed. In this analysis, the x- and y-type glutenin subunits showed similar interspecific relationships and differentiated rye from wheat and the Aegilops species. In both cases, the glutenin genes of Aegilops tauschii appeared closely related to the glutenins of the D genome, which, in turn, are closely related to those of Aegilops umbellulata. The homologous gene subunits of A. comosa and A. uniaristata from the section Comopyrum were grouped together. The glutenin gene of A. speltoides was grouped with the wheat B genome genes. This result reinforces the close relationships between the S and B genomes of Aegilops and Triticum, respectively.