title: Down-regulation of UDP-glucuronic acid biosynthesis leads to swollen plant cell walls and severe developmental defects associated with changes in pectic polysaccharides.
abstract: UDP-glucose dehydrogenase (UGD) plays a key role in the nucleotide sugar biosynthetic pathway, as its product UDP-glucuronic acid is the common precursor for arabinose, xylose, galacturonic acid, and apiose residues found in the cell wall. In this study we characterize an Arabidopsis thaliana double mutant ugd2,3 that lacks two of the four UGD isoforms. This mutant was obtained from a cross of ugd2 and ugd3 single mutants, which do not show phenotypical differences compared with the WT. In contrast, ugd2,3 has a strong dwarfed phenotype and often develops seedlings with severe root defects suggesting that the UGD2 and UGD3 isoforms act in concert. Differences in its cell wall composition in comparison to the WT were determined using biochemical methods indicating a significant reduction in arabinose, xylose, apiose, and galacturonic acid residues. Xyloglucan is less substituted with xylose, and pectins have a reduced amount of arabinan side chains. In particular, the amount of the apiose containing side chains A and B of rhamnogalacturonan II is strongly reduced, resulting in a swollen cell wall. The alternative pathway to UDP-glucuronic acid with the key enzyme myo-inositol oxygenase is not up-regulated in ugd2,3. The pathway also does not complement the ugd2,3 mutation, likely because the supply of myo-inositol is limited. Taken together, the presented data underline the importance of UDP GlcA for plant primary cell wall formation.
authors.affiliation: Department of Cell Biology, Molecular Cell Physiology, University of Salzburg, 5020 Salzburg, Austria.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Reboul
authors.forename: Claudia
authors.initials: C
authors.lastname: Geserick
authors.forename: Martin
authors.initials: M
authors.lastname: Pabst
authors.forename: Beat
authors.initials: B
authors.lastname: Frey
authors.forename: Doris
authors.initials: D
authors.lastname: Wittmann
authors.forename: Ursula
authors.initials: U
authors.lastname: Lütz-Meindl
authors.forename: Renaud
authors.initials: R
authors.lastname: Léonard
authors.forename: Raimund
authors.initials: R
authors.lastname: Tenhaken
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D002473:Cell Wall / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D009154:Mutation; D010368:Pectins / Q000096:biosynthesis* / Q000235:genetics; D014533:Uridine Diphosphate Glucose Dehydrogenase / Q000235:genetics / Q000378:metabolism; D014535:Uridine Diphosphate Glucuronic Acid / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D014535:Uridine Diphosphate Glucuronic Acid; D010368:Pectins; D014533:Uridine Diphosphate Glucose Dehydrogenase