Isolation and characterization of wheat ω-gliadin genes

The DNA sequences of two full-length wheat omega -gliadin prolamin genes (omega F20b and omega G3) containing significant 5' and 3' flanking DNA sequences are reported. The omega F20b DNA sequence contains an open reading frame encoding a 30,460-Dalton protein, whereas the omega G3 sequence would encode a putative 39,210-Dalton protein except for a stop codon at amino-acid residue position 165. These two omega -gliadin genes are closely related and are of the ARQ-/ARE-variant type as categorized by the derived N-terminal amino-acid sequences and aminoacid compositions. The omega -gliadins were believed be related to the omega -secalins of rye and the C-hordeins of barley, and analyses of these complete omega -gliadin sequences confirm this close relationship. Although the omega -type sequences from all three species are closely related, in this analysis the rye and barley co-type sequences are the most similar in a pairwise comparison. A comparison of omega -gliadin flanking sequences with respect to that of their orthologs and with respect to wheat gliadin genes suggests the conservation of flanking DNA necessary for gene function. Sequence data for members of all major wheat prolamin families are now available.