Cadmium stress induces changes in the lipid composition and biosynthesis in tomato (<Emphasis Type="Italic">Lycopersicon esculentum</Emphasis> Mill.) leaves |
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| Authors: | Wided Ben Ammar Issam Nouairi Mokhtar Zarrouk Fatma Jemal |
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| Institution: | (1) Unité de Recherche Nutrition et Métabolisme Azotés et Protéines de Stress (UR 99/09-20), Faculté des Sciences de Tunis, Campus Universitaire, 2092, Tunis El Manar, Tunisie, Tunisia;(2) Laboratoire Caractérisation et Qualité de l’Huile d’Olive, Centre de Biotechnologie de Borj Cedria, B.P. 901, 2050 Hammam-Lif, Tunisie, Tunisia |
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| Abstract: | The effects of cadmium (Cd) stress on lipid composition and biosynthesis were investigated in young leaves of ten-day-old
tomato seedlings (Lycopersicon esculentum Mill. cv. Ibiza F1). Cd was found to be mainly accumulated in roots, but a severe inhibition of biomass production occurred
in leaves, even at its low concentration (1.0 μM). Seven days after Cd treatment, the membrane lipids were extracted and separated
on silica-gel thin layer chromatography (TLC). Fatty acid methyl esters were analyzed by FID-GC on a capillary column. Our
results showed that Cd stress decreased the quantities of all lipids classes (phospholipids, galactolipids and neutral lipids).
Likewise, there was also a decline in the levels of tri-unsaturated fatty acids, such as linolenic (C18:3) and hexadecatrienoic
(C16:3) acids. The linolenic acid (C18:3) decreased in monogalactosyldiacylglycerol (MGDG) and all phospholipids, while hexadecatrienoinic
acid (C16:3) declined mainly in MGDG. Moreover, Cd at high concentrations (25.0 and 50.0 μM) significantly enhanced the levels
of lipid peroxides. Radiolabelling experiments were carried out by laying down microdroplets of 1-14C]acetate–a major precursor of lipid biosynthesis–on attached leaves of the control and Cd-treated plants. After incubation
for 1, 2, 12 and 24 h, the leaves were harvested and lipids extracted and analysed. Cd stress was found to decrease the incorporation
of 1-14C]acetate in total lipids. The biosynthesis of total lipids was altered with 25.0 and 50.0 μM Cd. The decline in the incorporation
of 1-14C]acetate due to Cd stress was observed in all lipid classes. There was also a substantial decline in the incorporation of
1-14C]acetate in tri-unsaturated fatty acids. The results indicate that Cd treatment induces an oxidative stress by inhibiting
the chloroplastic and extrachloroplastic lipid-biosynthesis pathways as well as lipid peroxidation. |
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| Keywords: | [1-14C]acetate Cadmium stress Fatty acids Lipid biosynthesis Lipid peroxidation Lycopersicon esculentum Radioactivity labelling |
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