Characterization of β-amylase and its deficiency in various rice cultivars

beta-Amylase deficiency in various cultivars of rice was examined at the molecular level. Using an antibody against beta-amylase purified from germinating seeds of rice, we were able to demonstrate the expression and organization of the beta-amylase gene in normal and deficient cultivars. Although beta-amylase is a starch-hydrolyzing enzyme, as is alpha-amylase, the beta-amylase protein/gene is expressed differently from the alpha-amylase protein/gene; i.e. (1) beta-amylase is synthesized only in aleurone cells, (2) the enzyme production in the embryo-less half-seeds is not under hormonal control, We identified some cultivars of rice that are deficient for beta-amylase activity. We present new evidence that synthesis is blocked at the level of mRNA synthesis in the deficient cultivars. The usefulness of beta-amylase as a crop trait is also discussed.