Sequence analysis of the 5' non-coding regions of active and inactive 1Ay HMW glutenin genes from wild and cultivated wheats

The genes encoding the HMW glutenin subunits belong to a small gene family where not all members are expressed in cultivated wheat varieties. In particular, the Ay HMW glutenin subunit is always absent. On the basis of nucleotide sequence comparisons of the putative promoter regions of the 1Ay gene of six different active HMW glutenin genes, it was previously hypothesized that the silencing of the 1Ay gene was caused by a few specific nucleotide substitutions in the 5' flanking region. The availability of wild wheat progenitors expressing the Ay glutenin subunit allowed us to compare the 5' flanking region of active and inactive genes. We have found a nearly perfect nucleotide sequence identity in this region between active and inactive 1Ay genes, and thus demonstrating that the inactivation of the gene encoding this subunit in cultivated wheats is not due to the 10 substitutions occurring in this region.