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Plant and Cell Physiology Advance Access published online on October 29, 2009
Plant and Cell Physiology, doi:10.1093/pcp/pcp144
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© The Author 2009. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org

Genetically Modified Arabidopsis Thaliana Cells Reveal The Involvement Of Mitochondrial Fatty Acid Composition In Membrane Basal And Uncoupling Protein Mediated Proton Leaks.

Cécile Hourton-Cabassa1, Ana Rita Matos1,2, Joao Arrabaça2, Chantal Demandre1, Alain Zachowski1 and François Moreau1

1 Université Pierre et Marie Curie (Paris 6), CNRS UR 5, 4 place Jussieu 75005 Paris, France
2 Departamento de Biologia Vegetal, Bio FIG, Faculdade de Ciências da Universidade de Lisboa, Centro de Engenharia Biológica, Campo Grande, 1749-016 Lisboa, Portugal

Corresponding author: Hourton-Cabassa Cécile Université Pierre et Marie Curie (Paris 6), CNRS UR 5, 4 place Jussieu 75005 Paris, France, Tel: + 33(0)1 44 27 96 47, Fax, +33 (0)1 44 27 61 51, E-mail cecile.cabassa{at}upmc.fr


  Abstract

We investigated the role of membrane fatty acids on basal proton leaks and uncoupling protein (UCP)-dependent proton conductance in Arabidopsis mitochondria. Using wild type cells, cold sensitive fad2 mutant cells, deficient in {omega}-6-oleate desaturase, and cold-tolerant FAD3+ transformant cells, over-expressing {omega}-3-linoleate desaturase, we showed that basal proton leak in non-phosphorylating state was dependent on lipid composition. The extent of membrane proton leak was drastically reduced in fad2 mutant, containing low amounts of polyunsaturated fatty acids. Conversely, this proton leak was higher in FAD3+ mitochondria that exhibit a higher polyunsaturated fatty acid content and high protein to lipid ratio. The dependency of membrane leaks upon membrane potential was higher in FAD3+ and lower in fad2. UCP content was higher in both fad2 mutant and FAD3+ transgenic lines compared to wild type cells and so was the UCP-activity, assayed by the reduction of phosphorylation yield (ADP/O) triggered by palmitate as UCP activator. This UCP assay was validated by measurements of UCP-proton leak in non-phosphorylating state (flux-force relationships between proton flux and membrane potential). The potential uncoupling capacity of UCP protein was high enough to allow the lost of respiratory control in the three genotypes. Taking together, data reported here suggest that the cold-tolerance of FAD3+ cells and the cold-sensitivity of fad2 cells are associated to changes in their mitochondrial membrane basal proton leaks, whereas, differences in functional expression of UCP are not simply related to cold adaptation in Arabidopsis cells.

Keywords: Arabidopsis thaliana - lipid desaturase mutants - membrane and fatty acid composition - membrane conductance - uncoupling protein - cold-sensitivity

(Received September 21, 2009; Accepted October 12, 2009)
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