title: Mitochondrial glycolate oxidation contributes to photorespiration in higher plants.
abstract: The oxidation of glycolate to glyoxylate is an important reaction step in photorespiration. Land plants and charophycean green algae oxidize glycolate in the peroxisome using oxygen as a co-factor, whereas chlorophycean green algae use a mitochondrial glycolate dehydrogenase (GDH) with organic co-factors. Previous analyses revealed the existence of a GDH in the mitochondria of Arabidopsis thaliana (AtGDH). In this study, the contribution of AtGDH to photorespiration was characterized. Both RNA abundance and mitochondrial GDH activity were up-regulated under photorespiratory growth conditions. Labelling experiments indicated that glycolate oxidation in mitochondrial extracts is coupled to CO(2) release. This effect could be enhanced by adding co-factors for aminotransferases, but is inhibited by the addition of glycine. T-DNA insertion lines for AtGDH show a drastic reduction in mitochondrial GDH activity and CO(2) release from glycolate. Furthermore, photorespiration is reduced in these mutant lines compared with the wild type, as revealed by determination of the post-illumination CO(2) burst and the glycine/serine ratio under photorespiratory growth conditions. The data show that mitochondrial glycolate oxidation contributes to photorespiration in higher plants. This indicates the conservation of chlorophycean photorespiration in streptophytes despite the evolution of leaf-type peroxisomes.
authors.affiliation: RWTH Aachen, Institute of Biology I, Worringer Weg 1, D-52056, Aachen, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Niessen
authors.forename: Krishnaveni
authors.initials: K
authors.lastname: Thiruveedhi
authors.forename: Ruben
authors.initials: R
authors.lastname: Rosenkranz
authors.forename: Rashad
authors.initials: R
authors.lastname: Kebeish
authors.forename: Heinz-Josef
authors.initials: HJ
authors.lastname: Hirsch
authors.forename: Fritz
authors.initials: F
authors.lastname: Kreuzaler
authors.forename: Christoph
authors.initials: C
authors.lastname: Peterhänsel
mesh_terms: D000429:Alcohol Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D006016:Glycolates / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D016254:Mutagenesis, Insertional; D010084:Oxidation-Reduction; D010788:Photosynthesis; D012333:RNA, Messenger / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D006016:Glycolates; D012333:RNA, Messenger; D002245:Carbon Dioxide; D000429:Alcohol Oxidoreductases; C525353:GDH protein, Arabidopsis