Expression analysis of α-gliadin isoforms in wheat grains.

Gliadin is a major wheat seed storage protein that affects the extensibility of flour dough. Multiple genes encode gliadin, and there are numerous isoforms encoded by these genes, some of which might be related to flour quality. In this study, gliadin isoforms encoded by 30 α-gliadin genes from the wheat cultivar "Chinese Spring" (CS) were identified using 2-DE and MS/MS. The chromosomes where these isoform genes are located were determined using Gli-2 locus-deficient lines. A quantitative analysis by 2-DE revealed differences in expression levels among α-gliadin isoforms. We also separated the polymer and monomer fractions of the total protein by SEC. We found that an α-gliadin isoform with 7 cysteine residues was present at relatively higher levels in the polymer fraction than an α-gliadin isoform with 6 cysteine residues. The present study results can help in understanding the relationship between the properties of α-gliadin isoforms and the physical properties of dough in the future. SIGNIFICANCE: For investigating the relationship between isoforms and dough extensibility, we identified α-gliadin isoforms encoded by 30 genes among the 50 genes cloned until date. Moreover, the polymer and monomer fractions of the total protein were separated by SEC. We found that an α-gliadin isoform with 7 cysteine residues was present at relatively higher levels in the polymer fraction than an α-gliadin isoform with 6 cysteine residues. This study provided useful information for elucidating the relationship between the properties of α-gliadin isoforms and the physical properties of dough.