The Influence of Abiotic Stresses on the Glycoglycerolipid Content in the Red Beetroot Vacuolar Membrane

The content of glycoglycerolipids (GL) in red beetroot vacuolar membrane under osmotic and oxidative stresses was investigated. Variations in the GL content in the stress conditions indicate an important role of these compounds in protective mechanisms. Vacuolar membrane GL levels and the ratio of digalactosyldiacylglycerols to monogalactosyldiacylglycerol (DGDG/MGDG) increased under hypoosmotic and oxidative conditions; these alterations contributing to membrane stabilization were similar to those observed in other cell membranes under stress condition. Variations in the GL content of vacuolar membrane produced by hyperosmotic stress notably differed from what was expected. The DGDG content and DGDG/MGDG ratio significantly decreased. These alterations did not necessarily result in a decrease in the membrane stability under hyperosmotic stress, since the content of MGDG involved in the formation of a hexagonal structure and capable of destabilizing lipid bilayer also decreased. The variations in vacuolar membrane GL levels under hyperosmotic stress can be associated with an increased degradation or reduced biosynthesis of GL and present yet another defense mechanism.