The wheat γ-gliadin genes:: characterization of ten new sequences and further understanding of γ-gliadin gene family structure

Ten new wheat gamma -gliadin gene sequences are reported and an analysis of gamma -gliadin gene family structure is carried out using all known gamma -gliadin sequences. The new sequences comprise four genomic clones with significantly more flanking DNA than previously reported, and six cDNA clones from a wheat endosperm EST project. Analysis of extended flanking DNA from the genomic clones indicates the limits of conservation of gamma -gliadin DNA sequence that are similar to those previously found with other gliadin and glutenin genes and that are theorized to define the DNA sequence necessary for gene control. Most of the flanking DNA is not homologous to any reported DNA sequence, and one flanking region contains the first MITE-like (miniature inverted transposable element) DNA sequence associated with gliadin genes. About a quarter of the encoded polypeptides would contain a free cysteine residue - an observation that may relate to reports that at least some gliadins can participate in wheat endosperm glutenin polymer formation. The new sequences represent both genes closely related to those previously reported and a new sub-class of gamma -gliadins.