Nutritional control of storage-protein synthesis in developing grain of barley (Hordeum vulgare L.)

Sulphur starvation of barley results in decreased accumulation of the "sulphur-rich" B-hordein polypeptides, with little or no effect on the 'sulphur-poor' C hordeins. The populations of mRNAs for C hordeins and the two major subfamilies of B-hordein polypeptides have been assessed by in-vitro translations in a wheat-germ extract and by 'dot' hybridisations to (32)P-labelled B- and C-hordein complementary-DNA clones. The results show that the relative changes in the rates of accumulation of the three groups of polypeptides are correlated with similar changes in the abundances of their respective mRNAs. In addition, the deficiency of sulphur also appears to increase the efficiency of translation of C-hordein mRNA and to decrease the efficiency of translation of the B-hordein mRNAs. Thus the results indicate that there may be two components to the effect of sulphur deficiency on hordein accumulation, one acting at the level of transcription, or mRNA degradation, and one at the level of translation.