Use of mitochondrial electron transport mutants to evaluate the effects of redox state on photosynthesis, stress tolerance and the integration of carbon/nitrogen metabolism.
Primary leaf metabolism requires the co-ordinated production and use of carbon skeletons and redox equivalents in several subcellular compartments. The role of the mitochondria in leaf metabolism has long been recognized, but it is only recently that molecular tools and mutants have become available to evaluate cause-and-effect relationships. In particular, analysis of the CMSII mutant of Nicotiana sylvestris, which lacks functional complex I, has provided information on the role of mitochondrial electron transport in leaf function. The essential feature of CMSII is the absence of a major NADH sink, i.e. complex I. This necessitates re-adjustment of whole-cell redox homeostasis, gene expression, and also influences metabolic pathways that use pyridine nucleotides. In air, CMSII is not able to use its photosynthetic capacity as well as the wild type. The mutant shows up-regulation of the leaf antioxidant system, lower leaf contents of reactive oxygen species, and enhanced stress resistance. Lastly, the loss of a major mitochondrial dehydrogenase has important repercussions for the integration of primary carbon and nitrogen metabolism, causing distinct changes in leaf organic acid profiles, and also affecting downstream processes such as the biosynthesis of the spectrum of leaf amino acids.
Noctor
Graham
G
Laboratoire Signalisation Redox, Institut de Biotechnologie des Plantes, Bâtiment 630, Université Paris XI,F-91405 Orsay cedex, France. noctor@ibp.u-psud.fr
Dutilleul
Christelle
C
De Paepe
Rosine
R
Foyer
Christine H
CH
D002245:Carbon Dioxide / Q000378:metabolism*; D019069:Cell Respiration / Q000502:physiology; D004579:Electron Transport / Q000235:genetics; D042967:Electron Transport Complex I / Q000235:genetics / Q000378:metabolism*; D008027:Light; D008928:Mitochondria / Q000235:genetics / Q000502:physiology*; D009154:Mutation; D009584:Nitrogen / Q000378:metabolism*; D010084:Oxidation-Reduction; D010788:Photosynthesis / Q000502:physiology*; D014026:Nicotiana / Q000235:genetics / Q000502:physiology*
D002245:Carbon Dioxide; D042967:Electron Transport Complex I; D009584:Nitrogen