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 acids. In the developing embryo of oilseed plants, the degree of saturation of C18 fatty acids is mainly controlled by the activity of the microsomal Delta 12 and 15 desaturases. We have constructed chimeric genes using a seed-specific promoter (AT2S2) and the coding sequences from Arabidopsis Delta 12 or rapeseed Delta 15 desaturases in two orientations 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 shows significant modifications of oleic, linoleic and alpha-linolenic acid content when compared with oil from the control plants. The sense strategy led mainly to an overexpression of the desaturase activity and in some cases to its inhibition, presumably by co-suppression or sense-suppression of the endogenous genes, while the antisense strategy gave a graded range of activity. These results highlight the advantages and limits of both strategies and complement results from work in soybean and rapeseed plants. Fatty acid synthesis during A. thaliana seed formation is a potentially useful model for production of other oils through modified desaturation patterns, including industrial oils with hydroxy, epoxy or elongated fatty acids. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.