Molar fractions of high-molecular-weight glutenin subunits are stable when wheat is grown under various mineral nutrition and temperature regimens

Abstract Molar fractions of the high-molecular-weight glutenin subunits (HMW-GS) were determined for flour from bread wheat ( Triticum aestivum L. cv Butte86) produced under 13 different combinations of temperature, water and mineral nutrition. Albumins, globulins and gliadins were removed from the flour by extraction with 0.3 M NaI in 7.5% 1-propanol. Total HMW-GS were recovered by extracting the remaining protein with 2% SDS and 25 mM DTT. Individual HMW-GS were then separated and quantified by RP-HPLC. Constant molar fractions for the five HMW-GS were maintained under all environmental conditions, despite large differences in duration of grain fill, total protein per grain, flour protein percentage, and total HMW-GS per grain. Similar molar fractions were found for five other US wheat varieties. The Bx7 subunit accumulated to the highest level at 30% of total HMW-GS. The Dx and Dy subunits were present in smaller but nearly equal proportions, 22% and 23%, respectively, and the Ax and By subunits were the least abundant, 14% and 12%, respectively. Although the amounts of HMW-GS per unit of flour are strongly affected by environment, the different subunits respond so similarly to external conditions that their final proportions appear to be determined mainly by genetic factors.