The role of ????6?￠????desaturase acyl?￠????carrier specificity in the efficient synthesis of long?￠????chain polyunsaturated fatty acids in transgenic plants

摘要

The role of acyl?￠????CoA?￠????dependent ????6?￠????desaturation in the heterologous synthesis of omega?￠????3 long?￠????chain polyunsaturated fatty acids was systematically evaluated in transgenic yeast and Arabidopsis thaliana . The acyl?￠????CoA ????6?￠????desaturase from the picoalga Ostreococcus tauri and orthologous activities from mouse ( Mus musculus ) and salmon ( Salmo salar ) were shown to generate substantial levels of ????6?￠????desaturated acyl?￠????CoAs, in contrast to the phospholipid?￠????dependent ????6?￠????desaturases from higher plants that failed to modify this metabolic pool. Transgenic plants expressing the acyl?￠????CoA ????6?￠????desaturases from either O.????tauri or salmon, in conjunction with the two additional activities required for the synthesis of C20 polyunsaturated fatty acids, contained higher levels of eicosapentaenoic acid compared with plants expressing the borage phospholipid?￠????dependent ????6?￠????desaturase. The use of acyl?￠????CoA?￠????dependent ????6?￠????desaturases almost completely abolished the accumulation of unwanted biosynthetic intermediates such as ???3?￠????linolenic acid in total seed lipids. Expression of acyl?￠????CoA ????6?￠????desaturases resulted in increased distribution of long?￠????chain polyunsaturated fatty acids in the polar lipids of transgenic plants, reflecting the larger substrate pool available for acylation by enzymes of the Kennedy pathway. Expression of the O.????tauri ????6?￠????desaturase in transgenic Camelina sativa plants also resulted in the accumulation of high levels of ????6?￠????desaturated fatty acids. This study provides evidence for the efficacy of using acyl?￠????CoA?￠????dependent ????6?￠????desaturases in the efficient metabolic engineering of transgenic plants with high value traits such as the synthesis of omega?￠????3 LC?￠????PUFAs.