Cereal Chem 54:646 - 656.  |  VIEW ARTICLE
Compositional Changes in the Developing Grain of High- and Low-Protein Wheats. II. Starch and Protein Synthetic Capacity.

G. R. Donovan, J. W. Lee, and R. D. Hill. Copyright 1977 by the American Association of Cereal Chemists, Inc. 

Metabolic properties of the developing kernels of high- and low-protein wheat cultivars (cv. Timgalen and cv. Heron, respectively) were examined in an attempt to account for their genotypically determined differences in protein content. No significant differences in DNA levels were observed in the two cultivars at any stage of development. Both ribosomal and total RNA were significantly higher in Timgalen than in Heron at most stages of development. Only slight differences in ribonuclease activity were observed in the two cultivars. Cut heads of Timgalen wheat, when immersed in solutions of 35S-cystine, incorporated isotope more rapidly into storage protein than did heads of Heron at the same stage of development. The results are consistent with a greater protein synthetic capacity and hence higher rate of conversion of amino acids into protein in Timgalen relative to Heron. Levels of the enzymes sucrose synthase, ADPG pyrophosphorylase, and starch synthase during development suggested that variations in carbohydrate metabolism were not responsible for differences in protein content between the two cultivars, but could be a significant factor in protein variability observed in a cultivar due to environmental influences. Higher growth temperatures, which induced more rapid accumulation of storage carbohydrate, produced higher enzyme levels but lower final storage carbohydrate.