TY - JOUR A1 - Engqvist, Martin K. M. A1 - Schmitz, Jessica A1 - Gertzmann, Anke A1 - Florian, Alexandra A1 - Jaspert, Nils A1 - Arif, Muhammad A1 - Balazadeh, Salma A1 - Müller-Röber, Bernd A1 - Fernie, Alisdair R. A1 - Maurino, Veronica G. T1 - GLYCOLATE OXIDASE3, a Glycolate Oxidase Homolog of Yeast L-Lactate Cytochrome c Oxidoreductase, Supports L-Lactate Oxidation in Roots of Arabidopsis JF - Plant physiology : an international journal devoted to physiology, biochemistry, cellular and molecular biology, biophysics and environmental biology of plants N2 - In roots of Arabidopsis (Arabidopsis thaliana), L-lactate is generated by the reduction of pyruvate via L-lactate dehydrogenase, but this enzyme does not efficiently catalyze the reverse reaction. Here, we identify the Arabidopsis glycolate oxidase (GOX) paralogs GOX1, GOX2, and GOX3 as putative L-lactate-metabolizing enzymes based on their homology to CYB2, the L-lactate cytochrome c oxidoreductase from the yeast Saccharomyces cerevisiae. We found that GOX3 uses L-lactate with a similar efficiency to glycolate; in contrast, the photorespiratory isoforms GOX1 and GOX2, which share similar enzymatic properties, use glycolate with much higher efficiencies than L-lactate. The key factor making GOX3 more efficient with L-lactate than GOX1 and GOX2 is a 5- to 10-fold lower Km for the substrate. Consequently, only GOX3 can efficiently metabolize L-lactate at low intracellular concentrations. Isotope tracer experiments as well as substrate toxicity tests using GOX3 loss-of-function and overexpressor plants indicate that L-lactate is metabolized in vivo by GOX3. Moreover, GOX3 rescues the lethal growth phenotype of a yeast strain lacking CYB2, which cannot grow on L-lactate as a sole carbon source. GOX3 is predominantly present in roots and mature to aging leaves but is largely absent from young photosynthetic leaves, indicating that it plays a role predominantly in heterotrophic rather than autotrophic tissues, at least under standard growth conditions. In roots of plants grown under normoxic conditions, loss of function of GOX3 induces metabolic rearrangements that mirror wild-type responses under hypoxia. Thus, we identified GOX3 as the enzyme that metabolizes L-lactate to pyruvate in vivo and hypothesize that it may ensure the sustainment of low levels of L-lactate after its formation under normoxia. Y1 - 2015 U6 - https://doi.org/10.1104/pp.15.01003 SN - 0032-0889 SN - 1532-2548 VL - 169 IS - 2 SP - 1042 EP - 1061 PB - American Society of Plant Physiologists CY - Rockville ER - TY - JOUR A1 - Balazadeh, Salma A1 - Jaspert, Nils A1 - Arif, Muhammad A1 - Müller-Röber, Bernd A1 - Maurino, Veronica G. T1 - Expression of ROS-responsive genes and transcription factors after metabolic formation of H2O2 in chloroplasts JF - Frontiers in plant science N2 - Glycolate oxidase (GO) catalyses the oxidation of glycolate to glyoxylate, thereby consuming O-2 and producing H2O2. In this work, Arabidopsis thaliana plants expressing GO in the chloroplasts (GO plants) were used to assess the expressional behavior of reactive oxygen species (ROS)-responsive genes and transcription factors (TFs) after metabolic induction of H2O2 formation in chloroplasts. In this organelle, GO uses the glycolate derived from the oxygenase activity of RubisCO. Here, to identify genes responding to an abrupt production of H2O2 in chloroplasts we used quantitative real-time PCR (qRT-PCR) to test the expression of 187 ROS-responsive genes and 1880 TFs after transferring GO and wild-type (WT) plants grown at high CO2 levels to ambient CO2 concentration. Our data revealed coordinated expression changes of genes of specific functional networks 0.5 h after metabolic induction of H2O2 production in GO plants, including the induction of indole glucosinolate and camalexin biosynthesis genes. Comparative analysis using available microarray data suggests that signals for the induction of these genes through H2O2 may originate in the chloroplast. The TF profiling indicated an up-regulation in GO plants of a group of genes involved in the regulation of proanthocyanidin and anthocyanin biosynthesis. Moreover, the upregulation of expression of IF and IF interacting proteins affecting development (e.g., cell division, stem branching, flowering time, flower development) would impact growth and reproductive capacity, resulting in altered development under conditions that promote the formation of H2O2. KW - glycolate oxidase KW - H2O2 KW - ROS-responsive genes KW - transcription factors Y1 - 2012 U6 - https://doi.org/10.3389/fpls.2012.00234 SN - 1664-462X VL - 3 PB - Frontiers Research Foundation CY - Lausanne ER -