title: Mitochondrial uncoupling protein is required for efficient photosynthesis.
abstract: Uncoupling proteins (UCPs) occur in the inner mitochondrial membrane and dissipate the proton gradient across this membrane that is normally used for ATP synthesis. Although the catalytic function and regulation of plant UCPs have been described, the physiological purpose of UCP in plants has not been established. Here, biochemical and physiological analyses of an insertional knockout of one of the Arabidopsis UCP genes (AtUCP1) are presented that resolve this issue. Absence of UCP1 results in localized oxidative stress but does not impair the ability of the plant to withstand a wide range of abiotic stresses. However, absence of UCP1 results in a photosynthetic phenotype. Specifically there is a restriction in photorespiration with a decrease in the rate of oxidation of photorespiratory glycine in the mitochondrion. This change leads to an associated reduced photosynthetic carbon assimilation rate. Collectively, these results suggest that the main physiological role of UCP1 in Arabidopsis leaves is related to maintaining the redox poise of the mitochondrial electron transport chain to facilitate photosynthetic metabolism.
authors.affiliation: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, United Kingdom. lee.sweetlove@plants.ox.ac.uk
authors.forename: Lee J
authors.initials: LJ
authors.lastname: Sweetlove
authors.forename: Anna
authors.initials: A
authors.lastname: Lytovchenko
authors.forename: Megan
authors.initials: M
authors.lastname: Morgan
authors.forename: Adriano
authors.initials: A
authors.lastname: Nunes-Nesi
authors.forename: Nicolas L
authors.initials: NL
authors.lastname: Taylor
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Baxter
authors.forename: Ira
authors.initials: I
authors.lastname: Eickmeier
authors.forename: Alisdair R
authors.initials: AR
authors.lastname: Fernie
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D015153:Blotting, Western; D002244:Carbon / Q000378:metabolism; D017931:DNA Primers; D005998:Glycine / Q000378:metabolism; D007473:Ion Channels / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000378:metabolism*; D018384:Oxidative Stress / Q000235:genetics; D010788:Photosynthesis / Q000235:genetics / Q000502:physiology*; D018515:Plant Leaves / Q000235:genetics / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000071256:Uncoupling Protein 1
chemical_list: D017931:DNA Primers; D007473:Ion Channels; D024101:Mitochondrial Proteins; D000071256:Uncoupling Protein 1; D002244:Carbon; D005998:Glycine