Journal Article

Sugar-Controlled Ca<sup>2+</sup> Uptake and <i>α</i>-Amylase Secretion in Cultured Cells of Rice (<i>Oryza sativa</i> L.)

Toshiaki Mitsui, Tadeusz Loboda, Akira Itoh and Taro Ikarashi

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 40, issue 8, pages 884-893
Published in print January 1999 | ISSN: 0032-0781
Published online January 1999 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/oxfordjournals.pcp.a029618
Sugar-Controlled Ca2+ Uptake and α-Amylase Secretion in Cultured Cells of Rice (Oryza sativa L.)

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Sugar starvation-induced synthesis and extracellular liberation of α-amylase molecules in suspension-cultured cells of rice (Oryza sativa L.) required Ca2+, although the level of translatable α-amylase mRNA was not affected in the presence of Ca2+. Sugar depletion markedly stimulated Ca2+ uptake by rice cells and sucrose supplementation reduced it. Immunohistochemical and electron probe microanalyzer studies indicated an apparent resemblance between the distribution pattern of Ca2+ and that of α-amylase molecules induced in the sugar-depleted cells. Ca2+ uptake was reduced by sucrose, maltose, fructose, and glucose similarly at more than 5 mM, but was unaffected by mannitol (88 mM), 6-deoxy-D-glucose (10 mM), and 3-O-methyl-D-glucose (10 mM). Furthermore, an effective Ca2+ channel blocker, La3+ significantly inhibited the Ca2+ uptake and the synthesis and extracellular liberation of α-amylase molecules in the absence of sucrose, while a general P-type ATPase inhibitor, vanadate greatly stimulated both in the presence of sucrose. We concluded that, by controlling the Ca2+ uptake, metabolic sugars regulate the protein synthesis and posttranslational secretory processes of α-amylase molecules in rice cells.

Keywords: α-Amylase (EC 3.2.1.1.) isoform; Ca2+ uptake; EPMA; Rice cells; Secretion; Sucrose

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Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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