COMPARISON OF SENSE AND ANTISENSE METHODOLOGIES FOR MODIFYING THE FATTY-ACID COMPOSITION OF ARABIDOPSIS-THALIANA OILSEED

The industrial usefulness and nutritional value of vegetable oils can be improved by modifying the levels of certain polyunsaturated fatty a cids. In the developing embryo of oilseed plants, the degree of satura tion of C18 fatty acids is mainly controlled by the activity of the mi crosomal Delta 12 and 15 desaturases. We have constructed chimeric gen es using a seed-specific promoter (AT2S2) and the coding sequences fro m Arabidopsis Delta 12 or rapeseed Delta 15 desaturases in two orienta tions in order to define the most efficient way to specifically modify the fatty acid composition of transgenic Arabidopsis thaliana seeds. Homozygous lines derived from >100 independent transgenic Arabidopsis plants were selected for the four constructs. Oil from their seeds sho ws significant modifications of oleic, linoleic and alpha-linolenic ac id content when compared with oil from the control plants. The sense s trategy led mainly to an overexpression of the desaturase activity and in some cases to its inhibition, presumably by co-suppression or sens e-suppression of the endogenous genes, while the antisense strategy ga ve a graded range of activity. These results highlight the advantages and limits of both strategies and complement results from work in soyb ean and rapeseed plants. Fatty acid synthesis during A. thaliana seed formation is a potentially useful model for production of other oils t hrough modified desaturation patterns, including industrial oils with hydroxy, epoxy or elongated fatty acids. (C) 1998 Elsevier Science Ire land Ltd. All rights reserved.