CHANGES IN PROTEIN COMPLEXES OF DURUM-WHEAT IN DEVELOPING SEED

End-use quality of wheat derives from the functional properties of its storage proteins. Storage proteins are synthesized during grain development and undergo modifications mainly during grain dehydration, with increased level of aggregation. This study was conducted to determine whether changes in protein complexes of durum wheat [Triticum turgidum (Desf.)] during seed development relate to seed quality. Protein extracts of developing seeds of cultivars Capdur and Tomclair were reduced and examined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Results confirmed synthesis of both gliadins and glutenin subunits early during maturation with qualitative compositions remaining nearly constant. Size-exclusion high-performance liquid chromatography (SE-HPLC) on unreduced protein extracts was used to follow quantitative changes in distribution of protein complexes. Among the five chromatographic fractions corresponding to different sizes of aggregates or monomers, F1 (excluded peak) and F2 (complexes of intermediate size) increased more rapidly in Capdur (good pasta quality) than in Tomclair (poor pasta quality). Characterization of the chromatographic fractions by electrophoresis showed that low-molecular-weight (LMW) subunits of glutenin are mainly involved in the largest complexes and are the ones most clearly showing differences between cultivars. The tendency of LMW subunits to aggregate during grain dehydration may help explain differences found in pasta quality among durum wheat cultivars.