Sequence variations and molecular phylogenetic analyses of the HMW-GS genes from different genomes in Triticeae

To investigate the molecular evolution of the high-molecular-weight glutenin subunits (HMW-GSs) in Triticeae, multiple sequence alignment was carried out on the N-terminal sequences of 77 HMW-GSs. The sequence of N-terminal domain showed high homology in both x- and y-type subunits. Sequence alignment of the N-terminal domain of y-type subunits suggested that they shared similar primary structure with each other, not only in the length variation of the N-terminal domain but also they have less variation in amino acids in this domain than those of x-type subunits. Analysis of the x-type HMW-GSs genes revealed that there were three conservative HMW-GSs gene groups with distinct fragments at the beginning of the N-terminal domains of ORFs, defined by the presence or absence of 24 bp fragment, and the presence of 15 bp fragment, respectively. The frequency of mutations in the x-type and y-type HMW-GSs genes was 1.89 and 1.25 out of 10 bases, respectively. Sequence analysis revealed that the y-type HMW-GSs did not contain enough variation for evolutionary analyses. It is obvious that the HMW-GSs encoded by genes of A, B and D genomes in common wheat formed three clusters. The x-type HMW-GSs from Aegilops bicornis, Aegilops comosa, Aegilops cylindrica, Aegilops umbellulata and Aegilops uniaristata were more closely related to the subunits from the D genome rather than those from the B genome.