title: Genetic evidence for the role of isopentenyl diphosphate isomerases in the mevalonate pathway and plant development in Arabidopsis.
abstract: Isopentenyl/dimethylallyl diphosphate isomerase (IPI) catalyzes the interconversion of isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP), which are the universal C(5) units of isoprenoids. In plants, IPP and DMAPP are synthesized via the cytosolic mevalonate (MVA) and plastidic methylerythritol phosphate (MEP) pathways, respectively. However, the role of IPI in each pathway and in plant development is unknown due to a lack of genetic studies using IPI-defective mutants. Here, we show that the atipi1atipi2 double mutant, which is defective in two Arabidopsis IPI isozymes, exhibits dwarfism and male sterility under long-day conditions and decreased pigmentation under continuous light, whereas the atipi1 and atipi2 single mutants are phenotypically normal. We also show that the sterol and ubiquinone levels in the double mutant are <50% of those in wild-type plants, and that the male-sterile phenotype is chemically complemented by squalene, a sterol precursor. In vivo isotope labeling experiments using the atipi1atipi2 double mutant revealed a decrease in the incorporation of MVA (in its lactone form) into sterols, with no decrease in the incorporation of MEP pathway intermediates into tocopherol. These results demonstrate a critical role for IPI in isoprenoid biosynthesis via the MVA pathway, and they imply that IPI is essential for the maintenance of appropriate levels of IPP and DMAPP in different subcellular compartments in plants.
authors.affiliation: Biotechnology Research Center, The University of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan. ukokada@mail.ecc.u-tokyo.ac.jp
authors.forename: Kazunori
authors.initials: K
authors.lastname: Okada
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kasahara
authors.forename: Shinjiro
authors.initials: S
authors.lastname: Yamaguchi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kawaide
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kamiya
authors.forename: Hideaki
authors.initials: H
authors.lastname: Nojiri
authors.forename: Hisakazu
authors.initials: H
authors.lastname: Yamane
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D002247:Carbon Isotopes; D019748:Carbon-Carbon Double Bond Isomerases / Q000235:genetics* / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D045782:Hemiterpenes; D008798:Mevalonic Acid / Q000031:analogs & derivatives / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D009928:Organ Specificity; D010641:Phenotype; D051479:Plant Infertility; D021381:Protein Transport; D013347:Subcellular Fractions / Q000201:enzymology; D013729:Terpenes / Q000378:metabolism; D014996:Xylulose / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: D002247:Carbon Isotopes; D045782:Hemiterpenes; D013729:Terpenes; D014996:Xylulose; C029724:1-deoxy-2-pentulose; C015367:mevalonolactone; D019748:Carbon-Carbon Double Bond Isomerases; C021453:isopentenyldiphosphate delta-isomerase; D008798:Mevalonic Acid