PROTEIN PHOSPHATASE INHIBITORS ENHANCE THE EXPRESSION OF AN ALPHA-AMYLASE GENE, ALPHA-AMY3, IN CULTURED RICE CELLS

A rice (Oryza sativa L.) gene for a-amylase, alpha AmyS, was strongly and rapidly induced by treatment of suspension-cultured cells with oka daic acid (OA), a potent and specific inhibitor of protein serine/thre onine phosphatases 1 and 2A. The massive accumulation of alpha Amy3 mR NB in response to OA treatment was due to the stimulation of gene tran scription and a partial stabilization of this mRNA. This induction of alpha AmyS message by OA occurred even though cellular protein synthes is was inhibited. Simultaneous treatment of cultured cells with OA and anisomycin synergistically induced alpha AmyS expression. In addition , the inhibition of protein synthesis stabilized OA-induced alpha Amy3 mRNA. In the presence of protein kinase inhibitors H7, W7, and H8, al pha Amy3 mRNA accumulation induced by OA was unaffected. These results indicate that OA-dependent alpha Amy3 induction is regulated transcri ptionally by a signal transduction pathway involving protein phosphory lation, but independent of both protein kinase C and Ca2+/calmodulin- or Ca2+-dependent protein kinases. Furthermore, an AMP-activated prote in kinase may be required for this induction of alpha AmY3 expression. (C) 1994 Academic Press, Inc.