SDS-insoluble glutenin polymer formation in developing grains of hexaploid wheat : role of the HMW-GS/LMW-GS ratio and the drying rate during ripening
Résumé
The accumulation of polymeric proteins and the changes in molecular size distribution of these proteins were followed during grain filling and/or premature desiccation. The accumulation behavior of polymeric proteins and their constituent polypeptides (high molecular weight and low molecular weight glutenin subunits) was determined by RP-HPLC using a NaI/propanol purification procedure. By using this new extraction and separation procedure, we have demonstrated that there was a coordinated initiation of storage protein biosynthesis even if the accumulation rate varied greatly between the two main classes of proteins (i.e., monomeric and polymeric fraction). Moreover, the glutenin subunit composition was largely modified during glutenin accumulation. Both the HMW-GS/LMW-GS and HMW-GS-x/HMW-GS-y ratios increased significantly during the whole cell enlargement phase (from 16 to 37 DAA). By applying premature grain desiccation during this physiological phase, we demonstrated that the polymerisation index (SDS-insoluble polymers/total polymers) of the glutenin polymers was closely related to the HMW-GS/LMW-GS ratio of these proteins. An increase in the relative proportion of HMW-GS in glutenins caused the proportion of SDS-insoluble polymers to rise during grain desiccation. From these studies, it appears that the modification of the desiccation rate (grain desiccation at a constant temperature with variable relative humidity levels) induced a parallel modification of the glutenin insolubilisation rate but did not affect the polymerisation index of the glutenins at maturity.
Domaines
Sciences du Vivant [q-bio]
Origine : Fichiers produits par l'(les) auteur(s)