title: Mitochondrial Dihydrolipoyl Dehydrogenase Activity Shapes Photosynthesis and Photorespiration of Arabidopsis thaliana.
abstract: Mitochondrial dihydrolipoyl dehydrogenase (mtLPD; L-protein) is an integral component of several multienzyme systems involved in the tricarboxylic acid (TCA) cycle, photorespiration, and the degradation of branched-chain α-ketoacids. The majority of the mtLPD present in photosynthesizing tissue is used for glycine decarboxylase (GDC), necessary for the high-flux photorespiratory glycine-into-serine conversion. We previously suggested that GDC activity could be a signal in a regulatory network that adjusts carbon flux through the Calvin-Benson cycle in response to photorespiration. Here, we show that elevated GDC L-protein activity significantly alters several diagnostic parameters of cellular metabolism and leaf gas exchange in Arabidopsis thaliana. Overexpressor lines displayed markedly decreased steady state contents of TCA cycle and photorespiratory intermediates as well as elevated NAD(P)(+)-to-NAD(P)H ratios. Additionally, increased rates of CO2 assimilation, photorespiration, and plant growth were observed. Intriguingly, however, day respiration rates remained unaffected. By contrast, respiration was enhanced in the first half of the dark phase but depressed in the second. We also observed enhanced sucrose biosynthesis in the light in combination with a lower diel magnitude of starch accumulation and breakdown. These data thus substantiate our prior hypothesis that facilitating flux through the photorespiratory pathway stimulates photosynthetic CO2 assimilation in the Calvin-Benson cycle. They furthermore suggest that this regulation is, at least in part, dependent on increased light-capture/use efficiency.
authors.affiliation: Plant Physiology Department, University of Rostock, D-18051 Rostock, Germany stefan.timm@uni-rostock.de.
authors.forename: Stefan
authors.identifier: http://orcid.org/0000-0003-3105-6296
authors.initials: S
authors.lastname: Timm
authors.affiliation: Plant Physiology Department, University of Rostock, D-18051 Rostock, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Wittmiß
authors.affiliation: Plant Physiology Department, University of Rostock, D-18051 Rostock, Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: Gamlien
authors.affiliation: Plant Physiology Department, University of Rostock, D-18051 Rostock, Germany.
authors.forename: Ralph
authors.initials: R
authors.lastname: Ewald
authors.affiliation: Max Planck Institute of Molecular Plant Physiology, D-14476 Potsdam-Golm, Germany.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Florian
authors.affiliation: Medical Biology and Electron Microscopy Centre, University Medicine Rostock, D-18057 Rostock, Germany.
authors.forename: Marcus
authors.identifier: http://orcid.org/0000-0002-2517-4440
authors.initials: M
authors.lastname: Frank
authors.affiliation: Centre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany.
authors.forename: Markus
authors.identifier: http://orcid.org/0000-0001-7790-4022
authors.initials: M
authors.lastname: Wirtz
authors.affiliation: Centre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany.
authors.forename: Rüdiger
authors.identifier: http://orcid.org/0000-0002-6238-4818
authors.initials: R
authors.lastname: Hell
authors.affiliation: Max Planck Institute of Molecular Plant Physiology, D-14476 Potsdam-Golm, Germany.
authors.forename: Alisdair R
authors.initials: AR
authors.lastname: Fernie
authors.affiliation: Plant Physiology Department, University of Rostock, D-18051 Rostock, Germany.
authors.forename: Hermann
authors.identifier: http://orcid.org/0000-0001-7802-8925
authors.initials: H
authors.lastname: Bauwe
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*; D018533:Biomass; D002247:Carbon Isotopes; D019069:Cell Respiration / Q000528:radiation effects; D002734:Chlorophyll / Q000378:metabolism; D002952:Citric Acid Cycle / Q000528:radiation effects; D008058:Dihydrolipoamide Dehydrogenase / Q000378:metabolism*; D005740:Gases / Q000378:metabolism; D008027:Light; D055442:Metabolome / Q000528:radiation effects; D008928:Mitochondria / Q000201:enzymology* / Q000528:radiation effects; D009249:NADP / Q000378:metabolism; D009711:Nucleotides / Q000378:metabolism; D010641:Phenotype; D010788:Photosynthesis / Q000528:radiation effects; D018515:Plant Leaves / Q000378:metabolism / Q000528:radiation effects / Q000648:ultrastructure; D030821:Plants, Genetically Modified; D011725:Pyridines / Q000378:metabolism; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism; D012995:Solubility; D013213:Starch / Q000378:metabolism; D013440:Sulfides / Q000378:metabolism
chemical_list: D002247:Carbon Isotopes; D005740:Gases; D009711:Nucleotides; D011725:Pyridines; D013440:Sulfides; D002734:Chlorophyll; D009249:NADP; D013213:Starch; D008058:Dihydrolipoamide Dehydrogenase; D012273:Ribulose-Bisphosphate Carboxylase; C023666:pyridine