Effets du cadmium sur le métabolisme des lipides de plantules de colza (Brassica napus L.)

Abstract

Cadmium effects on lipid metabolism of rape (Brassica napus L.). Treatment of rape seedlings with increasing CdCl 2 concentrations in the culture medium resulted in a cadmium accumulation within plant tissues, which increased with external metal dose; such accumulation was more important in roots than in leaves. Biomass production was severely inhibited, even at low cadmium concentration. In leaves, quantities of chloroplastic lipids, monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulfolipids (SL) and phosphatidylglycerol (PG) decreased sharply under metallic treatment. However, contents of extrachloroplastic lipids, mainly phosphatidylcholine (PC) and phosphatidylethanolamine (PE) increased significantly. In contrast to leaves, contents of root phospholipids decreased. Likewise, levels of tri-unsaturated fatty acids: linolenic (C18:3) and hexadecatrienoïc (C16:3) dropped in leaves of treated seedlings as compared to those of controls, suggesting that heavy metals induced an alteration in the fatty acid desaturation process or a stimulation of their peroxidation. Also, trans palmitoleic acid (C16:1-trans) level in PG decreased considerably. In roots, there was a slight decrease in C18:3 level, with a concomitant increase in the C18:2 percentage. Radioactive labelling of leaf lipids with (1-14 C) acetate allowed to show that fatty acid biosynthesis was noticeably altered at the highest cadmium dose used (50 µM). Biosynthesis of tri-unsaturated fatty acids was also inhibited which may explain the decline in non-labelled lipid contents. Results showed that metallic ion seems to affect selectively chloroplastic membranes due to an inhibition of polyunsaturated fatty acid biosynthesis. Moreover, a lipid peroxidation occurred in our case because of the spectacular increase of malondialdehyde (MDA) content observed in cadmium treated leaves. To cite this article: N.

Changes in lipid composition, water relations and gas exchange in leaves of two young ‘Chemlali’ and ‘Chetoui’ olive trees in response to water stress

“…Specifically, elevated 18:3 in membrane lipids has been associated with increased cold tolerance (Graham and Patterson 1982) and with defense under drought stress (Sgherri et al 1996;Repellin et al 1997). However, other authors found a decrease in the unsaturation level in Brassicaceae (Ben Youssef et al 2005;Nouairi et al 2006) and tomato (Lycopersicon esculentum Mill.) (Ben Ammar et al 2007), in response to cadmium stress.…”

Antioxidative response to cadmium in roots and leaves of tomato plants

“…It is well established that photosynthesis , mineral nutrition, membrane structure, etc., are affected by the presence of Cd (Ben Ammar et al 2005). Besides, Cd induced peroxidation of membrane lipids by generating reactive oxygen species (ROS) (Dixit et al 2001, Ben Youssef et al 2005.…”

Cadmium stress induces changes in the lipid composition and biosynthesis in tomato (Lycopersicon esculentum Mill.) leaves

“…Indeed, alterations in the activities of enzymes, such as fatty acid synthase and oleoyl-ACP desaturase (Jones and Harwood 1993) are probably related to the affinity of heavy metals for sulfhydryl groups, which results in an inhibition of the active sites of enzymes and/or conformational modifications of macromolecules (Cumming and Taylor 1990). In many plant species, Cd is known to modify the membrane composition and integrity by altering the total lipid composition (Ouariti et al 1997;Jemal et al 2002;Ben Youssef et al 2003;Djebali et al 2005;Nouairi et al 2006). In all these studies, the decrease in polar lipid content has been attributed to changes in galactolipid levels.…”

“…It has been demonstrated that Cd may induce membrane lipid peroxidation by generating reactive oxygen species (ROS), which initiate peroxidation of unsaturated lipids (Ben Youssef et al 2005). Lipid peroxidation is a complex process, which is normally initiated following the abstraction of a hydrogen atom from endogenous unsaturated fatty acids, resulting in the production of lipid radicals.…”