title: The Arabidopsis thaliana Myo-inositol 1-phosphate synthase1 gene is required for Myo-inositol synthesis and suppression of cell death.
abstract: l-myo-inositol 1-phosphate synthase (MIPS; EC 5.5.1.4) catalyzes the rate-limiting step in the synthesis of myo-inositol, a critical compound in the cell. Plants contain multiple MIPS genes, which encode highly similar enzymes. We characterized the expression patterns of the three MIPS genes in Arabidopsis thaliana and found that MIPS1 is expressed in most cell types and developmental stages, while MIPS2 and MIPS3 are mainly restricted to vascular or related tissues. MIPS1, but not MIPS2 or MIPS3, is required for seed development, for physiological responses to salt and abscisic acid, and to suppress cell death. Specifically, a loss in MIPS1 resulted in smaller plants with curly leaves and spontaneous production of lesions. The mips1 mutants have lower myo-inositol, ascorbic acid, and phosphatidylinositol levels, while basal levels of inositol (1,4,5)P(3) are not altered in mips1 mutants. Furthermore, mips1 mutants exhibited elevated levels of ceramides, sphingolipid precursors associated with cell death, and were complemented by a MIPS1-green fluorescent protein (GFP) fusion construct. MIPS1-, MIPS2-, and MIPS3-GFP each localized to the cytoplasm. Thus, MIPS1 has a significant impact on myo-inositol levels that is critical for maintaining levels of ascorbic acid, phosphatidylinositol, and ceramides that regulate growth, development, and cell death.
authors.affiliation: Department of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, USA.
authors.forename: Janet L
authors.initials: JL
authors.lastname: Donahue
authors.forename: Shannon R
authors.initials: SR
authors.lastname: Alford
authors.forename: Javad
authors.initials: J
authors.lastname: Torabinejad
authors.forename: Rachel E
authors.initials: RE
authors.lastname: Kerwin
authors.forename: Aida
authors.initials: A
authors.lastname: Nourbakhsh
authors.forename: W Keith
authors.initials: WK
authors.lastname: Ray
authors.forename: Marcy
authors.initials: M
authors.lastname: Hernick
authors.forename: Xinyi
authors.initials: X
authors.lastname: Huang
authors.forename: Blair M
authors.initials: BM
authors.lastname: Lyons
authors.forename: Pyae P
authors.initials: PP
authors.lastname: Hein
authors.forename: Glenda E
authors.initials: GE
authors.lastname: Gillaspy
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001205:Ascorbic Acid / Q000378:metabolism; D016923:Cell Death; D002518:Ceramides / Q000378:metabolism; D018744:DNA, Plant / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D007294:Inositol / Q000096:biosynthesis*; D016254:Mutagenesis, Insertional; D009154:Mutation; D007296:Myo-Inositol-1-Phosphate Synthase / Q000235:genetics* / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D002518:Ceramides; D018744:DNA, Plant; D010716:Phosphatidylinositols; D007294:Inositol; D007296:Myo-Inositol-1-Phosphate Synthase; D001205:Ascorbic Acid