Sub-families of hordein mRNA encoded at the Hor 2 locus of barley

Previous studies indicated that the Hor2 locus of barley, which specifies B hordein, is a complex family of genes derived from the duplication and divergence of a single ancestral gene. In vitro translation of poly A⁺ RNA from developing endosperms of seven cultivars shows that the hordein polymorphism is not due to post-translational modification of a few polypeptides. Each polypeptide appears to be specified by a separate mRNA and presumably a separate gene. Cloned cDNAs derived from B hordein mRNAs were used to select mRNAs from endosperms of seven barley cultivars with different Hor2 alleles. Comparison of the products of translation of these hybrid-selected mRNAs indicated the presence of two sub-families of B hordein mRNAs which code for different classes of hordein polypeptides previously recognized on the basis of cyanogen bromide peptide mapping. The proportions of the mRNAs for the two sub-families of B hordein polypeptides appeared to be correlated with the amounts of the polypeptides present in the endosperms.