title: Phytic acid synthesis and vacuolar accumulation in suspension-cultured cells of Catharanthus roseus induced by high concentration of inorganic phosphate and cations.
abstract: We have established a new system for studying phytic acid, myo-inositol hexakisphosphate (InsP(6)) synthesis in suspension-cultured cells of Catharanthus. InsP(6) and other intermediates of myo-inositol (Ins) phosphate metabolism were measured using an ion chromatography method. The detection limit for InsP(6) was less than 50 nM, which was sufficient to analyze Ins phosphates in living cells. Synthesis of Ins phosphates was induced by incubation in high inorganic phosphate medium. InsP(6) was mainly accumulated in vacuoles and was enhanced when cells were grown in high concentration of inorganic phosphates with the cations K(+), Ca(2+), or Zn(2+). However, there was a strong tendency for InsP(6) to accumulate in the vacuole in the presence of Ca(2+) and in nonvacuolar compartments when supplied with Zn(2+), possibly due to precipitation of InsP(6) with Zn(2+) in the cytosol. A vesicle transport inhibitor, brefeldin A, stimulated InsP(6) accumulation. The amounts of both Ins(3)P(1) myo-inositol monophosphate synthase, a key enzyme for InsP(6) synthesis, and Ins(1,4,5)P(3) kinase were unrelated to the level of accumulation of InsP(6). The mechanisms for InsP(6) synthesis and localization into vacuoles in plant cells are discussed.
authors.affiliation: Japan Society for the Promotion of Science, Tokyo 102-8471, Japan.
authors.forename: Naoto
authors.initials: N
authors.lastname: Mitsuhashi
authors.forename: Miwa
authors.initials: M
authors.lastname: Ohnishi
authors.forename: Yoko
authors.initials: Y
authors.lastname: Sekiguchi
authors.forename: Yong-Uk
authors.initials: YU
authors.lastname: Kwon
authors.forename: Young-Tae
authors.initials: YT
authors.lastname: Chang
authors.forename: Sung-Kee
authors.initials: SK
authors.lastname: Chung
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Inoue
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Reid
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Yagisawa
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Mimura
mesh_terms: D002118:Calcium / Q000494:pharmacology; D030008:Catharanthus / Q000378:metabolism*; D002412:Cations / Q000494:pharmacology*; D002478:Cells, Cultured; D007295:Inositol Phosphates / Q000378:metabolism; D007700:Kinetics; D010710:Phosphates / Q000494:pharmacology*; D010833:Phytic Acid / Q000096:biosynthesis*; D011188:Potassium / Q000494:pharmacology; D014617:Vacuoles / Q000187:drug effects / Q000378:metabolism*; D015032:Zinc / Q000378:metabolism / Q000494:pharmacology
chemical_list: D002412:Cations; D007295:Inositol Phosphates; D010710:Phosphates; D010833:Phytic Acid; D015032:Zinc; D011188:Potassium; D002118:Calcium