Ben Youssef Nabil, Nouairi Issam, Ben Temime Sonia, Taamalli Wael, Zarrouk Mokhtar, Ghorbal Mohamed Habib, Ben Miled Daoud Douja
Laboratoire Caractérisation et qualité de l'huile d'olive, INRST, BP 95-2050 Hammam-Lif, Tunisie.
C R Biol. 2005 Aug;328(8):745-57. doi: 10.1016/j.crvi.2005.05.010.
Treatment of rape seedlings with increasing CdCl2 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 (1-14C) acetate allowed to show that fatty acid biosynthesis was noticeably altered at the highest cadmium dose used (50 microM). 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.
在培养基中用不断增加的氯化镉浓度处理油菜幼苗，导致植物组织内镉积累，且随着外部金属剂量增加而增加；这种积累在根部比在叶片中更显著。即使在低镉浓度下，生物量生产也受到严重抑制。在叶片中，金属处理下叶绿体脂质、单半乳糖二酰基甘油（MGDG）、二半乳糖二酰基甘油（DGDG）、硫脂（SL）和磷脂酰甘油（PG）的含量急剧下降。然而，叶绿体外脂质的含量，主要是磷脂酰胆碱（PC）和磷脂酰乙醇胺（PE）显著增加。与叶片相反，根磷脂的含量下降。同样，与对照相比，处理过的幼苗叶片中三不饱和脂肪酸：亚麻酸（C18:3）和十六碳三烯酸（C16:3）的水平下降，表明重金属诱导了脂肪酸去饱和过程的改变或对其过氧化的刺激。此外，PG中的反式棕榈油酸（C16:1 - trans）水平大幅下降。在根部，C18:3水平略有下降，同时C18:2百分比增加。用（1 - 14C）乙酸对叶片脂质进行放射性标记表明，在所用的最高镉剂量（50 microM）下，脂肪酸生物合成明显改变。三不饱和脂肪酸的生物合成也受到抑制，这可能解释了未标记脂质含量的下降。结果表明，金属离子似乎由于抑制多不饱和脂肪酸生物合成而选择性地影响叶绿体膜。此外，在我们的实验中发生了脂质过氧化，因为在镉处理的叶片中观察到丙二醛（MDA）含量大幅增加。
