Characterisation and chromosomal localisation of C-type low-molecular-weight glutenin subunits in the bread wheat cultivar Chinese Spring

Low-molecular-weight glutenin subunits are classically divided into the B, C and D groups. Most attention has been paid to the characterisation of the B and D groups, whereas C subunits, although represented by a large number of protein components, have not been thoroughly characterised, mainly because they tend to separate with the gliadins in many fractionation procedures. Here we describe a procedure for obtaining a fraction strongly enriched in C subunits that has allowed us to determine the chromosomal location of these subunits in the bread wheat cultivar Chinese Spring. This analysis has shown that these subunits are coded on chromosome groups 1 and 6. Comparison between N-terminal amino acid sequencing of B and C subunits has shown that, whereas the former group includes mainly subunits with typical LMW-GS type sequences (76%), the C subunit group is made up almost completely of subunits with gliadin-like sequences (95%), including the α-type. These results indicate that the LMW-GSs are likely to be coded not only by the typical Glu-3 loci, but also by loci tightly linked to, and possibly included within, the Gli-1 and Gli-2 loci.