Phosphate modulates Ca2+ uptake and α-amylase secretion in suspension-cultured cells of rice

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Effects of phosphate on the Ca2+ uptake and the sucrose-controlled secretion of α-amylase molecules in cultured rice cells were investigated. Phosphate markedly stimulated Ca2+ uptake into rice cells, particularly at the outer cell layer of the cell cluster. Phosphate also increased the synthesis and extracellular liberation of α-amylase II-4 in sucrose-supplemented cells. The distribution pattern of enzyme in rice cell clusters induced by phosphate was similar to that of Ca2+ uptake. Phosphate did not increase the level of mRNA of α-amylase II-4, indicating that phosphate stimulates the translation and posttranslational secretory processes of α-amylase II-4 in the presence of sucrose. Furthermore, phosphate enhanced both the Ca2+ uptake and α-amylase II-4 synthesis in the microsomes. These results strongly suggested that the ratio of phosphate to sugar is important for regulating the Ca2+ uptake, and that phosphate and sugar precisely coordinate the Ca2+-mediated synthesis and extracellular liberation of α-amylase II-4.
日本植物細胞分子生物学会の論文
2003-06-00