title: Uric acid accumulation in an Arabidopsis urate oxidase mutant impairs seedling establishment by blocking peroxisome maintenance.
abstract: Purine nucleotides can be fully catabolized by plants to recycle nutrients. We have isolated a urate oxidase (uox) mutant of Arabidopsis thaliana that accumulates uric acid in all tissues, especially in the developing embryo. The mutant displays a reduced germination rate and is unable to establish autotrophic growth due to severe inhibition of cotyledon development and nutrient mobilization from the lipid reserves in the cotyledons. The uox mutant phenotype is suppressed in a xanthine dehydrogenase (xdh) uox double mutant, demonstrating that the underlying cause is not the defective purine base catabolism, or the lack of UOX per se, but the elevated uric acid concentration in the embryo. Remarkably, xanthine accumulates to similar levels in the xdh mutant without toxicity. This is paralleled in humans, where hyperuricemia is associated with many diseases whereas xanthinuria is asymptomatic. Searching for the molecular cause of uric acid toxicity, we discovered a local defect of peroxisomes (glyoxysomes) mostly confined to the cotyledons of the mature embryos, which resulted in the accumulation of free fatty acids in dry seeds. The peroxisomal defect explains the developmental phenotypes of the uox mutant, drawing a novel link between uric acid and peroxisome function, which may be relevant beyond plants.
authors: Freie Universität Berlin, Dahlem Centre of Plant Sciences, Department of Plant Biochemistry, 14195 Berlin, Germany.
authors: Oliver K
authors: OK
authors: Hauck
authors: Freie Universität Berlin, Dahlem Centre of Plant Sciences, Department of Plant Biochemistry, 14195 Berlin, Germany.
authors: Jana
authors: J
authors: Scharnberg
authors: Freie Universität Berlin, Dahlem Centre of Plant Sciences, Department of Plant Biochemistry, 14195 Berlin, Germany.
authors: Nieves Medina
authors: NM
authors: Escobar
authors: Biozentrum der Ludwig-Maximillians-Universität München, 82152 Planegg-Martinsried, Germany.
authors: Gerhard
authors: G
authors: Wanner
authors: Max-Planck-Institute for Molecular Plant Physiology, 14476 Potsdam, Germany.
authors: Patrick
authors: P
authors: Giavalisco
authors: Freie Universität Berlin, Dahlem Centre of Plant Sciences, Department of Plant Biochemistry, 14195 Berlin, Germany cpwitte@zedat.fu-berlin.de.
authors: Claus-Peter
authors: http://orcid.org/0000-0002-3617-7807
authors: CP
authors: Witte
mesh_terms: D017360:Arabidopsis / Q000196:embryology / Q000201:enzymology* / Q000235:genetics / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D018548:Cotyledon / Q000196:embryology / Q000201:enzymology / Q000235:genetics / Q000648:ultrastructure; D005227:Fatty Acids / Q000378:metabolism; D018525:Germination; D009154:Mutation; D020675:Peroxisomes / Q000378:metabolism*; D010641:Phenotype; D035261:Plant Components, Aerial / Q000196:embryology / Q000201:enzymology / Q000235:genetics / Q000648:ultrastructure; D011401:Promoter Regions, Genetic / Q000235:genetics; D011685:Purine Nucleotides / Q000378:metabolism; D036226:Seedlings / Q000196:embryology / Q000201:enzymology / Q000235:genetics / Q000648:ultrastructure; D012639:Seeds / Q000196:embryology / Q000201:enzymology / Q000235:genetics / Q000648:ultrastructure; D014503:Urate Oxidase / Q000235:genetics / Q000378:metabolism*; D014527:Uric Acid / Q000737:chemistry / Q000378:metabolism*; D019820:Xanthine / Q000737:chemistry / Q000378:metabolism; D014968:Xanthine Dehydrogenase / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D005227:Fatty Acids; D011685:Purine Nucleotides; D019820:Xanthine; D014527:Uric Acid; D014968:Xanthine Dehydrogenase; D014503:Urate Oxidase