Plant and Cell Physiology Advance Access published online on May 15, 2007
Plant and Cell Physiology, doi:10.1093/pcp/pcm061
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Alternative oxidase involvement in cold stress response of Arabidopsis thaliana fad2 and FAD3+ cell suspensions altered in membrane lipid composition
1 : Université Pierre et Marie Curie-Paris 6, C.N.R.S, UMR 7180 Physiologie Cellulaire et Moléculaire des Plantes, Le Raphaël, 3 Rue Galilée, Ivry sur Seine, F-94200, France
2 : Centro de Engenharia Biológica, Secção de Fisiologia e Bioquímica Vegetais, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal.
Corresponding author: Ana Rita Matos. Centro de Engenharia Biológica, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal. Telephone number: +351217500000, ext n°: 24350, Fax n°: +351217500166, e-mail address: armatos{at}fc.ul.pt
| Abstract |
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To investigate how the fatty acid composition of membrane lipids influences cell growth and mitochondrial respiration, in particular the alternative oxidase expression and capacity, under cold stress, we used the Arabidopsis thaliana fad2 knockout and FAD3+ overexpressing cultured cells lines affected in extrachloroplastic fatty acid desaturation activities. At 22 °C fad2 mitochondria exhibited a low polyunsaturated fatty acid content and low protein to lipid ratio while mitochondria from FAD3+ were enriched in linolenic acid and in total membrane protein. As a consequence both mutants showed a higher membrane microviscosity than the wild type. After exposure to 9 °C FAD3+ mitochondria exhibited lower microviscosity and lower rigidification upon a temperature downshift than fad2 . Furthermore, the extent of reduction of cell growth and respiratiory rates in the phosphorylating state was positively related to the cold sensitivity of each cell line, being more pronounced in fad2 that in WT, whereas the stability of those parameters reflected the cold-resistance of FAD3+ . By contrast, an increase in AOX capacity was observed in the three cell lines at 9 °C. These inductions were correlated to AOX protein amounts and seem to result from an accumulation of AOX1c transcripts in the three cell lines and of AOX1a transcripts in WT and fad2 cells. The fact that there is no direct relationship between the degree of cold tolerance of each cell line and their ability to enhance their AOX capacity suggests that the participation of AOX in Arabidopsis cells response to cold stress does not necessarily favours cold-tolerance.
Keywords: Alternative oxidase - Arabidopsis thaliana - fatty acid desaturase - mitochondria - low temperature
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