A ?-hordein gene

Abstract

The 1614 bp nucleotide sequence of a barley gene encoding a γ-hordein endosperm storage polypeptide is presented. The deduced amino acid sequence is 305 amino acids long. It comprises a 19 amino acid signal peptide, an N-terminal half composed of proline-glutamine blocks organized in repeating units and a C-terminal half where the repeats are dispersed and less conserved. The deduced amino acid sequence shows strong homology to a γ-gliadin polypeptide from wheat and a γ-secalin polypeptide from rye and less homology to a B1 hordein polypeptide from barley. The 378 bp 5' non-coding region contains a TATA box at-85, an AGGA sequence at-105 and a-300 element typical of prolamin storage protein genes. The transcript start is 56 bp upstream of the ATG codon and 30 bp downstream of the TATA box. The 318 bp 3' non-coding region contains 2 putative polyadenylation signals, 76 and 132 bp downstream of the stop codon. γ-Hordein polypeptides are encoded by a small multigene family. The γ-hordein gene family is not part of the deleted chromosome 5 region, containing the Hor 2 locus, in the B hordein-deficient mutant hor 2ca. Two mRNA size classes of 1350 and 1450 nt are detectable in wild-type endosperms from 8 to 26 days after anthesis. The mutant hor 2ca contains as much γ-hordein mRNA as the wild type, whereas the B and C hordein-deficient mutant lys 3a contains barely detectable amounts.