Conservation and variability of wheat alpha/beta-gliadin genes.

We have sequenced two genomic clones for wheat alpha/beta-gliadin storage protein genes. Comparison with a known sequence reveals close homology between the three and confirms the previously suspected evolutionary relatedness of members of this gliadin family. The coding region can be divided into six domains. Two unusual structures were found within this region: (i) The P-boxes which are composed of 12 codons, six of which are for proline, that are tandemly repeated four or five times; and (ii) Two polyglutamine stretches which consist of 18-22 tandemly repeated glutamine codons in one case, and 7-28 in the second. Analysis of the P-box structures revealed that certain mutations were probably present in the hypothetical ancestral alpha/beta-gliadin gene prior to gene multiplication. None of the genes have introns. All of the genes appear to contain typical eukaryotic promoters and also possess the double polyadenylation signal of plants.