Characterization and Classification of LMW-GS Genes at the Glu-3 Locus of Bread Wheat

Low Molecular Weight Glutenin Subunits (LMW-GS) proteins have great effects on the end-use quality of bread wheat and are difficult to differentiate directly. It is very important to characterize and classify LMW-GS genes systematically. In this paper, 692 complete Glu-3 gene sequences were retrieved from GenBank and were grouped based on their sequence characters and variations. Based on the characters of their N-terminal sequences, these genes were classified into two types, LMW-m and LMW-i, of which LMW-m genes were further classified into three sub-types based on their first amino acid (AA) (LMW-M, LMW-V and LMW-I). Based on the first seven or eight AA variations in the N-terminal sequence, LMW-GS Glu-3 genes were classified into 16 types, namely LMW-N1 to LMW-N16. Based on the last 10 AA variations in the C-terminal, the Glu-3 genes were classified into 22 types, designated as LMW-C1 to LMW-C22. Based on the number and distribution of cysteines, the Glu-3 genes classified into 22 types included 7 conventional types with eight cysteines and 15 variant types with seven or nine cysteines. In addition, two new Glu-A3 genes (GluA-10 and GluA-11) were identified based on their sequence homology, and the connection between different classification methods was analyzed briefly. The results provide insight into the nature of the Glu-3 gene family and are valuable for molecular marker-assisted selection of end-use quality traits in wheat improvement.