Biochemical and genetic characterization of a monomeric storage protein (T1) with an unusually high molecular weight in Triticum tauschii

The protein named T1, present in Triticum tauschii, was previously characterized as a high-molecular-weight (HMW) glutenin subunit with a molecular size similar to that of the y-type glutenin subunit-10 of Triticum aestivum. This protein was present along with other HMW glutenin subunits named 2t and T2, and was considered as part of the same allele at the Glu-D(t)1 locus of T. tauschii. This paper describes a re-evaluation of this protein, involving analyses of a collection of 173 accessions of T. tauschii, by SDS-PAGE of glutenin subunits after the extraction of monomeric protein. No accessions were found containing the three HMW glutenin subunits. On the other hand, 17 lines with HMW glutenin subunits having electrophoretic mobilities similar to subunits 2t and T2 were identified. The absence of T1 protein in these gel patterns has shown that protein T1 is not a component of the polymeric protein. Rather, the T1 protein is an omega-gliadin with an unusually high-molecular-weight. This conclusion is based on acidic polyacrylamide gel electrophoresis (A-PAGE), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and two-dimensional gel electrophoresis (A-PAGE+SDS-PAGE), together with analysis of its N-terminal amino-acids sequence. The inheritance of omega-gliadin T1 was studied through analyses of gliadins and HMW glutenins in 106 F2 grains of a cross between synthetic wheat, L/18913, and the wheat cv Egret. HMW glutenin subunits and gliadins derived from T. tauschii (Glu-D(t)1 and Gli-D(t)1) segregated as alleles of the Glu-D1 and Gli-D1 loci of bread wheat. A new locus encoding the omega-gliadin T1 was identified and named Gli-DT1. The genetic distance between this new locus and those of endosperm proteins encoded at the 1D chromosome were calculated. The Gli-DT1 locus is located on the short arm of chromosome 1D and the map distance between this locus and the Gli-D1 and Glu-D1 loci was calculated as 13.18 cM and 40.20 cM, respectively.