Weather variations in Sweden result in differences in the bread-making quality of wheat. This study investigated whether the variation in bread-making quality caused by yearly weather fluctuations could be explained by variation in protein composition, amount of storage proteins, protein subunits and protein groups, and relative amount and size distribution of polymeric proteins. Four spring wheat (Triticum aestivum L) cultivars grown in Sweden during three different years were investigated. Bread-making quality and gluten strength were measured using baking and glutograph tests. SDS-PAGE, SE-HPLC, RP-HPLC and ELISA were applied for investigation of protein composition, amount of storage proteins, protein subunits and protein groups, and relative amount and size distribution of polymeric proteins. The bread volume within cultivars varied depending on the cultivation year. The highest gluten strength was found in 1994 and the weakest in 1991. Variation in composition or relative amount of specific storage proteins, protein subunits or protein groups could not explain the variation in gluten strength between years. Instead, a significant relationship was found between the cultivation year and the percentage of unextractable polymeric protein in the total polymeric protein. The percentage of unextractable polymeric protein in the total polymeric protein was found to be highest during years when gluten strength was also high.
Pierce's disease (PD) is a destructive bacterial disease of grapes caused by Xylella fastidiosa which is xylem-confined. The tolerance level to this disease varies among Vitis species. Our research was aimed at identifying unique xylem sap proteins present in PD-tolerant Vitis species. The results showed wide variation in the xylem sap protein composition, where a set of polypeptides with pI between 4.5 and 4.7 and M(r) of 31 kDa were present in abundant amount in muscadine (Vitis rotundifolia, PD-tolerant), in reduced levels in Florida hybrid bunch (Vitis spp., PD-tolerant) and absent in bunch grapes (Vitis vinifera, PD-susceptible). Liquid chromatography/mass spectrometry/mass spectrometry analysis of these proteins revealed their similarity to beta-1, 3-glucanase, peroxidase, and a subunit of oxygen-evolving enhancer protein 1, which are known to play role in defense and oxygen generation. In addition, the amount of free amino acids and soluble sugars was found to be significantly lower in xylem sap of muscadine genotypes compared to V. vinifera genotypes, indicating that the higher nutritional value of bunch grape sap may be more suitable for Xylella growth. These data suggest that the presence of these unique proteins in xylem sap is vital for PD tolerance in muscadine and Florida hybrid bunch grapes.
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