Japanese sake-brewing rice cultivars show high levels of globulin-like protein and a chloroplast stromal HSP70
White-core is an important trait in the selection of rice (Oryza sativa L. ssp. japonica) for sake (Japanese rice wine) production. The present study was conducted to find differences between the endosperm protein pattern of white-core–bearing sake-brewing cultivars and those of normal rice grains. Protein patterns of white-core sake-brewing grains were compared with those of normal cultivars by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). Several proteins showing different amounts were detected. These were identified by microsequencing and found to be known carbohydrate-metabolizing enzymes as well as proteins with no known involvement in carbohydrate metabolism. Two units of globulin-like protein (GLP) and a chloroplast stromal heat shock protein 70 (ctHSP70) showed the greatest difference in the white-core group. Analysis of amyloplast proteins showed slightly higher amounts of GLP and ctHSP70 in the amyloplast than in the cytosol. Also, time-course analysis of developing rice grains indicated that both proteins were elevated during the later stages of grain development. From this we conclude that GLP and ctHSP70-II are associated with white-core appearance and thus behave as biochemical markers for this character in sake-brewing rice cultivars.