Planta (1983)159:366-372 P l a n t a 9 Springer-Verlag 1983 Nutritional control of storage-protein synthesis in developing grain of barley (Hordeum vulgare L.) S. Rahman, P.R. Shewry, B.G. Forde, M. Kreis and B.J. Miflin Biochemistry Department, Rothamsted Experimental Station, Harpenden, Herts. AL5 2JQ, UK Abstract. 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 sub- families of B-hordein polypeptides have been as- sessed by in-vitro translations in a wheat-germ ex- tract and by 'dot' hybridisations to 32p-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 poly- peptides are correlated with similar changes in the abundances of their respective mRNAs. In addi- tion, the deficiency of sulphur also appears to in- crease the efficiency of translation of C-hordein mRNA and to decrease the efficiency of transla- tion of the B-hordein mRNAs. Thus the results indicate that there may be two components to the effect of sulphur deficiency on hordein accumula- tion, one acting at the level of transcription, or mRNA degradation, and one at the level of trans- lation. Key words: Complementary DNA clones - Endo- sperm (hordein synthesis) - Hordein - Hordeum (protein synthesis) - mRNA - Protein synthesis (in vitro). Introduction The storage proteins of seeds are a complex mix- ture of components which provide a store of nitro- gen and sulphur for germination (Miflin and Shewry 1981). In accordance with this dual func- Abbreviations: cDNA=complementary DNA; PAGE=poly- acrylamide-gel electrophoresis; Poly(A)+RNA=polyadeny - lated RNA; SDS = sodium dodecylsulphate tion, the storage proteins of many species can be classified into at least two groups which differ in the relative amounts of the sulphur-containing amino acids, cysteine and methionine. For exam- ple, in legumes the 11S, or legumin-type proteins, form the sulphur-rich group and the 7S, or vicilin- type proteins, the sulphur-poor group (Derbyshire et al. 1976). In wheat and rye, the c~-gliadins and e~-secalins respectively are sulphur-poor whereas the other major groups of storage proteins are sul- phur-rich (Miflin et al. 1983 a). In barley, the B and C hordeins together ac- count for about 95% of the total alcohol-soluble storage proteins (Shewry et al. 1983 b). The B hor- deins contain about 2.5mol % cysteine and 0.6 tool % methionine whereas C hordeins contain no cysteine and only a trace of methionine (Shewry et al. 1980b). A third hordein group, D hordein, accounts for less than 5% of the total (Shewry et al. 1983b) and has an intermediate content of sulphur-amino acids (Field et al. 1982). Sodium- dodecylsulphate polyacrylamide-gel electrophore- sis (SDS-PAGE) of hordein from the cultivar Sun- dance shows that B hordein consists of two major doublets of MrS 35,000 (called B1) and 46,000 (B3) with minor bands between them (B2). In the C- hordein region there is a major group of bands of M r 59,000 (C1) and a minor band of M r 72,000 (C2). The D hordein is a single band of M r 105,000. Further resolution of the component polypeptides can be achieved by two-dimensional gel electro- phoresis (Rahman et al. 1982). Genetic analysis shows that although B, C and D hordein are com- plex mixtures of components, they appear to be coded for by single structural loci, called Hor 2, Hor 1 and Hor 3 respectively, which are located on chromosome 5 (Shewry et al. 1980, 1983a; Jen- sen et al. 1980). It has been proposed that these