Distribution of fatty acids in polar and neutral lipids during seed development in Arabidopsis thaliana genetically engineered to produce acetylenic, epoxy and hydroxy fatty acids

Abstract

Genetically engineered plants of Arabidopsis thaliana containing either the Crepis alpina linoleate delta 12-acetylenase gene, the Crepis palaestina linoleate delta 12-epoxygenase gene under transcriptional control of a napin promoter or a Lesquerella fendleri oleate hydroxylase under the transcriptional control of the endogenous promoter were analysed for the distribution of fatty acids. Seed samples were analysed from 9 to 23 days after pollination (DAP) as well as mature seeds. The relative amount of oleate was higher and the amount of the polyunsaturated fatty acids was lower in the seeds of the transgenic plants expressing the fatty acid modifying genes than in seeds from the control plants. The degree of the changes was more pronounced in phosphatidylcholine (PC) than in the neutral fraction and varied considerably between the transgenic plants carrying the different genes. The unusual fatty acids (acetylenic, epoxy and hydroxy fatty acids) produced in the transgenic A. thaliana plants accumulated in significant amounts in seed phospholipids during seed development. Despite that the percentage of the unusual fatty acids accumulated in neutral lipids in the transgenic plants were 5–35 times less than in the wild plant species accumulating these acids, the relative levels of these acids in PC were approximately the same (epoxy and hydroxy fatty acids) or much higher (acetylenic fatty acids) than in that lipid in the wild plants. Since ricinoleic, vernolic and crepenynic acid are formed from precursor fatty acids esterified in PC catalysed by delta 12-desaturase like enzymes, it can be concluded that A. thaliana seeds have less efficient mechanisms for the specific channelling of these fatty acids from PC to triacylglycerol (TAG).