Wheat Storage Proteins

Abstract

A total RNA extract was prepared from developing wheat seeds using guanidine-HCl to eliminate endogenous RNase activity. The RNA preparation, substantially free of protein, carbohydrate and DNA, was chromatographed on either a polyuridylic acid-agarose or polyguanylic acid-agarose column to yield a gliadin-enriched mRNA fraction. Only slight differences occurred for the products synthesized in a wheat germ cell-free translation system when either polyadenylic acid-enriched or cytosine-rich RNA was used as a template. This is consistent with the high proline content of the gliadins and indicates that a large proportion of the mRNA activity in these RNA preparations is directed toward gliadin synthesis. After a 2nd affinity chromatography step, the gliadin-enriched mRNA fraction was fractionated by 2 cycles on sucrose-density gradient centrifugation under denaturing conditions. The RNA sedimented as a broad band with a peak at 14S and a shoulder at the 11S region of the sucrose gradient. RNA from the peak 14S fraction translated predominantly the 2 major gliadin polypeptides which had MW of 34,000 and 36,000. Analysis of the 14S RNA by methylmercury hydroxide-agarose gel electrophoresis revealed the presence of a predominant RNA species with a MW of 415,000 (1200 nucleotides).