Uric Acid Accumulation in an Arabidopsis Urate Oxidase Mutant Impairs Seedling Establishment by Blocking Peroxisome Maintenance. Issue 7 (22nd July 2014)

• Record Type: Journal Article
• Authors: Hauck, Oliver K.; Scharnberg, Jana; Escobar, Nieves Medina; Wanner, Gerhard; Giavalisco, Patrick; Witte, Claus-Peter
• Is Part Of: The Plant Cell. Volume 26:Issue 7(2014)
• Page Start: 3090
• Page End: 3100
• Publication Date: 2014-07-22
• DOI: 10.1105/tpc.114.124008
• Languages: English
• ISSNs: 1040-4651

Abstract

Abstract : Arabidopsis seeds with a mutation in urate oxidase show a defect in germination, fail to develop the cotyledons, and exhibit partially blocked β-oxidation. These phenotypes result from the accumulation of uric acid and are suppressed by the additional mutation of xanthine dehydrogenase, which prevents uric acid accumulation. The data presented show that peroxisome maintenance is compromised by uric acid. 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.