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 devel opment 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 turgidu m (Desf.)] during seed development relate to seed quality. Protein ext racts of developing seeds of cultivars Capdur and Tomclair were reduce d and examined by sodium dodecyl sulfate polyacrylamide gel electropho resis (SDS-PAGE). Results confirmed synthesis of both gliadins and glu tenin subunits early during maturation with qualitative compositions r emaining nearly constant. Size-exclusion high-performance liquid chrom atography (SE-HPLC) on unreduced protein extracts was used to follow q uantitative changes in distribution of protein complexes. Among the fi ve chromatographic fractions corresponding to different sizes of aggre gates or monomers, F1 (excluded peak) and F2 (complexes of intermediat e 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) s ubunits of glutenin are mainly involved in the largest complexes and a re the ones most clearly showing differences between cultivars. The te ndency of LMW subunits to aggregate during grain dehydration may help explain differences found in pasta quality among durum wheat cultivars .