Abstract:

Using degenerate oligonucleotide primers and genomic PCR reactions, the complete coding region sequences of two 1Ay high molecular weight (HMW) glutenin subunit genes were amplified from Triticum urartu accessions that showed differential expression of the 1Ay HMW glutenin subunits in their seeds. The coding sequence amplified from the accession that expressed the 1Ay gene (Tu1Ay-e) was highly homologous to that of known y type HMW glutenin subunit genes. Consequently, the primary structure of the protein translated from the coding sequence of Tu1Ay-e was identical to that of previously published y type subunits. Bacterial expression of the coding sequence of Tu1Ay-e produced a polypeptide identical to the 1Ay subunit extracted from seeds, indicating that the cloned sequence was an accurate representation of the original coding region of Tu1Ay-e. In contrast, the coding region sequence amplified from the accession that did not express 1Ay subunit contained three in-frame premature stop codons. Based on past findings on silenced HMW glutenin subunit genes, we conclude that the presence of in-frame premature stop codon(s) is an important feature of the silenced 1Ay gene (Tu1Ay-s) in T. urartu. The potential value of the active 1Ay gene in improving the end use quality of common wheat and the mechanism underlying 1Ay gene silencing are discussed.

Key words: high molecular weight glutenin subunit, 1Ay, Triticum urartu , common wheat