[Sequences variation and classification of B-hordein genes in hull-less barley from Qinghai-Tibet Plateau]

The goal of this study is to understand the evolution relationship of the members of B-hordein gene family in hull-less barley by analysis of their structure and to explore their utility in grain quality improvement. Six copies of B-hordein gene (Hn1-Hn3, Hn7-Hn9) were cloned from six hull-less barley cultivars collected from Qinghai-Tibet Plateau and molecularly characterized. Comparison of their predicted polypeptide sequences with the published suggested that they all share the same basic protein structures. In addition, we found that the C-terminal end sequences of all B-hordeins shared a similar feature. In the six clones and the other three published (Hn4, Hn5 and Hn6) from hull-less barley, Hn2 and Hn7 contained identical C-terminal end sequence DIMPVDFWH, Hn3, Hn4, Hn5, Hn8 and Hn9 also shared the common sequence DIMPPDFWH, which was similar to that of a B-hordein reported previously. Both Hnl and Hn6 exhibited differences in their C-terminal end sequences, and they clustered into different subgroups. The B-hordeins with identical C-terminal end sequences were clustered into a same subgroup, so we believe that B-hordein gene subfamilies possibly can be classified on the basis of the conserved C-terminal end sequences of predicted polypeptide. Phylogenetic analysis also indicated that there is a relatively weak identity between our predicted B-hordeins and those reported from H. chilense and H. brevisubulatum. All of our nine predicted B-hordeins were clustered together and other B-hordeins formed another cluster. The possible use of these genes in relation to the barley quality is discussed.