High Oleic Sunflower: Studies on Composition and Desaturation of Acyl Groups in Different Lipids and Organs

Abstract

Abstract A selection of lipids from achenes, cotyledons after germination, roots and leaves of normal and high oleic varieties of sunflower were analyzed with regard to their fatty acid profiles. The lipids included triacylglycerol and phosphatidylcholine as ER-made components and mono-and digalactosyl diacylglycerol as plastid-localized glycolipids. A comparison of fatty acid pat­ terns showed that the block in oleate desaturation of the high oleic variety is confined to the ER of fat accumulating embryos, but that upon germination the oleate desaturation in the cotyledonary ER is rapidly derepressed. These data are supported by enzymatic experiments. In microsomes from maturing fruits of the high oleic variety oleoyl-phosphatidylcholine desaturase could not be detected, whereas o leoyl-CoA : lyso-phosphatidylcholine acyltransferase and components of the microsomal electron transport chains were not affected. A correlation in the expression of desaturation blocks in seed and root fatty acids as observed in mutants of other species was not observed which, therefore, cannot be generalized. Our data are discussed in terms of the existence of two ER-specific oleate desaturase activities.