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Huguet-Robert, V.,Sulpice, R.,Lefort, C.,Maerskalck, V.,Emery, N.,Larher, F. R.
2003
January
The suppression of osmoinduced proline response of Brassica napus L. var oleifera leaf discs by polyunsaturated fatty acids and methyl-jasmonate
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164
11
119
127
When subjected in vitro to upshock osmotic stress, canola leaf discs accumulate large amounts of proline. In this study, we investigated the regulatory effect exerted on the osmoinduced proline response by polyunsaturated fatty acids (PUFAs) and derivatives of the oxylipin pathway. When supplied to the stressing medium, PUFAs were found to inhibit proline accumulation, with alpha and gamma-linolenic acid (C18:3) being more effective than linoleic acid (C 18:2). The amount of accumulated proline increased to 200 pmol g(-1) dry weight (DW) and remained constant in leaf discs subjected for 8 h to a stress medium containing 3 50 g l(-1) PEG 6000 added with PUFAs, compared with levels observed in control discs treated with PEG that continued to increase to approximately 600 pmol g(-1) DW regularly for up to 24 It. The suppressing effect of PUFAs was mimicked by methyl-jasmonate (Me-JA). Whatever the mediator used, this effect was dependent on its concentration and on the moment when osmotic stress was applied: gamma-C18:3 > alpha-C18:3 > C18:2. An identical effect was observed with 12-oxo-phytodienoic acid (12-OPDA). In addition, the suppressing effect of Me-JA was found to counteract the promoting effect of abscisic acid (ABA). Collectively, these results demonstrated that proline accumulation by canola leaf explants subjected in vitro to osmotic stress could be partly suppressed by exogenously supplied free fatty acids (FAs) and by products resulting from their hydroperoxidation by lipoxygenase (LOXs). The physiological relevance of these findings is discussed. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.When subjected in vitro to upshock osmotic stress, canola leaf discs accumulate large amounts of proline. In this study, we investigated the regulatory effect exerted on the osmoinduced proline response by polyunsaturated fatty acids (PUFAs) and derivatives of the oxylipin pathway. When supplied to the stressing medium, PUFAs were found to inhibit proline accumulation, with alpha and gamma-linolenic acid (C18:3) being more effective than linoleic acid (C 18:2). The amount of accumulated proline increased to 200 pmol g(-1) dry weight (DW) and remained constant in leaf discs subjected for 8 h to a stress medium containing 3 50 g l(-1) PEG 6000 added with PUFAs, compared with levels observed in control discs treated with PEG that continued to increase to approximately 600 pmol g(-1) DW regularly for up to 24 It. The suppressing effect of PUFAs was mimicked by methyl-jasmonate (Me-JA). Whatever the mediator used, this effect was dependent on its concentration and on the moment when osmotic stress was applied: gamma-C18:3 > alpha-C18:3 > C18:2. An identical effect was observed with 12-oxo-phytodienoic acid (12-OPDA). In addition, the suppressing effect of Me-JA was found to counteract the promoting effect of abscisic acid (ABA). Collectively, these results demonstrated that proline accumulation by canola leaf explants subjected in vitro to osmotic stress could be partly suppressed by exogenously supplied free fatty acids (FAs) and by products resulting from their hydroperoxidation by lipoxygenase (LOXs). The physiological relevance of these findings is discussed. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.
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