The induction of α‐amylase activity by sucrose starvation in suspension‐cultured rice cells is regulated by polyamines

Abstract

The induction of a-amylase activily by sucrose starvation in suspension-cultured rice cells is regulated by polvamines. -Physiol. Plant. 91: 137-140.When suspension-cultured rice [Oryza sativa L. cv. Tainan 5) cells were deprived of sucrose, a-amylase (EC 3.2.1.1) activity in the cells and the culture medium increased markedly. The increase in activity of a-amy!ase caused by sucrose staivation in the cells and the medium was strongly reduced in the presence of exogenously added speniiine. Putrescine and spermidine also inhibited, thotigh only slightly, the increase in a-amylase activity caused by sucrose starvation. Preincubation of the enzyme extract or enzyme in the medium with polyamines had no effect on a-amylase activity. Sucrose starvation resulted in lower polyamine levels in rice suspension cells, D-Arginine and a-methylomithine, inhibitors of polyamine biosynthesis, caused reduced levels of poiyamines and increased activity of a-amyiase in rice suspension cells cultured in the presence of sucrose. Our results indicate that the induction of a-amylase activity by sucrose starvation in rice suspension cells is mediated, at least partly, through tbe intemal level of polyamines.