N-Terminal Amino Acid Sequences of γ-Gliadins from Bread Wheats

Abstract

Present-day bread wheats are hexaploid in nature (genomes designated AABBDD), having evolved from crosses between different diploid grass species, followed by chromosome doubling. γ-Gliadin protein components have been purified from the endosperm of a bread wheat cultivar (Triticum aestivum) and characterized according to electrophoretic patterns and N-terminal amino acid sequences. In addition, proteins with electrophoretic mobilities comparable to γ-gliadins were purified from three diploid species, T. monococcum, Aegilops speltoides, and Ae. squarrosa, that are likely candidates for being the progenitors of the A, B, and D genomes of T. aestivum. N-terminal amino acid sequences of these proteins were determined and found to be comparable to either γ₂- or γ₃-type gliadins from T. aestivum. The protein from T. monococcum differed slightly in sequence from the proteins from Ae. speltoides and Ae. squarrosa, which were identical in sequence to their equivalents in the hexaploid. This difference may be an example of divergence between the genera Triticum and Aegilops, expecially if both the γ₂- and γ₃-gliadins of the hexaploid were contributed by species of Aegilops.