Osmotic stress induced alterations in fatty acid composition and other metabolic responses in seedlings of Sinapis alba

Abstract

Sinapis alba L. (white mustard), an annual member of Brassicaceae, is an important oilseed crop with significant agronomic traits including tolerance to abiotic stress. The present study was aimed to assess the changes in biochemical attributes of S. alba, mainly the composition of lipids and fatty acids, in response to osmotic stress. Seedlings were subjected to stress condition by growing them on media supplemented with three different concentrations of polyethylene glycol (PEG 6000) solutions, respectively with ‑0.04, ‑0.16 and ‑0.64 MPa osmotic potential. Compatible solute content, lipid content, and lipid peroxidation of the seedlings were measured. Total fatty acid composition was analysed by gas chromatography mass spectrometry. Overall negative impact of PEG-mediated osmotic stress was apparent from seedling morphology. Total lipid content decreased in stressed plants together with increased level of triacylglycerol. Increase of lipid peroxidation in stressed condition indicated suppression of membrane integrity. The key outcome was the significant increase of unsaturation level of fatty acids due to higher accumulation of linoleic acid, α-linolenic acid and erucic acid in the seedlings exposed to higher osmotic stress. The results indicate that, in white mustard, the biochemical changes induced by osmotic stress mainly depend on changes in lipid composition and fatty acid unsaturation level, which maintain membrane stability during the early stage of seedling development.