A HIGH-MOLECULAR-WEIGHT SUBUNIT OF WHEAT GLUTENIN SEED STORAGE PROTEIN CORRELATES WITH ITS FLOUR QUALITY

The high molecular weight (HMW) subunits of wheat seed storage proteins in 376 cultivars were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The highest molecular weight subunit designated as 145 kD subunit was found frequently in Japanese cultivars (Fig. 1). This subunit has identical electrophoretic mobility of the glutenin high molecular weight subunit 2.2 as reported by PAYNE et al. (1983). The 145 kD subunit separated by SDS-PAGE was electroblotted onto a polyvinylidene difluoride membrane filter and the blotted subunit was sequenced by a gas-phase sequencer. The N-terminal amino acid sequence of the 145 kD subunit determined was consistent with that of the HMW glutenin subunits reported previously (Table 1). The 145 kD subunit was concluded to be one of the glutenin seed storage proteins. The size and number of hard crystal particles which characterize hard wheat flours (Fig. 2), varied depending on the presence or absence of the glutenin 145 kD subunit (Table 2); The cultivars without the 145 kD subunit always produce hard flours. The cultivars with the 145 kD subunit was higher in the southern part of Japan than the northern part (Fig. 3); Most of the cultivars predominant to the northern part of Japan (Hokkaido, Tohoku, Hokuriku and Nagano Districts) have no 145 kD subunit but many large crystal particles in the flours. However, most of the cultivars in the south Japan (Kyushu District) have this subunit but not many large crystal particles. These results suggest that the 145 kD subunit plays an important role in determining the hardness of wheat flours. The crossing test revealed that the expression of the 145 kD subunit is controlled by a single gene (Table 3, Fig. 4). The trace back of pedigree shows that the genotypes with and without the 145 kD subunit were preferably selected in each step of the wheat breeding procedures in the southern and northern part of Japan, respectively (Fig. 5).