Synthesis and secretion of α-amylase by rice callus: Evidence for differential gene expression

Rice seed callus expressed and secreted α-amylase at high levels. Twenty percent of the protein secreted by the callus was α-amylase. The callus secreted about 840 μg α-amylase with 10.9 x 10³ units of activity per gram dry weight callus per day. The α-amylase from callus exhibited a more complex isoform pattern than the germinating seed α-amylase. In addition, the level of mRNA expression by the five α-amylase gene groups was markedly different between callus and the germinating seed. The rice callus culture has features which make it attractive as a potential system for expressing proteins in plant cell fermentation systems.