Acyltransferases from basic science to modified seed oils

Different discrete acyltransferases are involved in glycerolipid biosynthesis, which occurs in plastids, mitochondria and endomembranes, mainly in the endoplasmic reticulum of plant cells. In each compartment a glycerol-3-phosphate and 1-acylglycerol-3-phosphate acyltransferase catalyze the stepwise acylation of glycerol-3-phosphate to 1,2-diacylglycerol-3-phosphate, the key intermediate in the biosynthesis of the various glycerolipids. These acyltansferases play an important role in establishing the typical fatty acid patterns of the major polar membrane lipids. This also holds true for the microsomal acyltransferases involved in triacylglycerol synthesis where a 1,2-diacylglycerol acyltransferase catalyzes the third acylation reaction. Consequently, the activities of plant acyltransferases are indispensable for the formation of both membrane and storage lipids, and their properties can be decisive determinants of certain plant traits. Recently, the importance of acyltransferases, especially of 1-acylglycerol-3-phosphate acyltransferases, in determining oil quality and usability for specific markets has been confirmed by genetic engineering. Chimeric 1-acylglycerol-3-phosphate acyltransferase genes have been successfully utilized to achieve the synthesis of rapeseed oil with homogeneous fatty acid distributions, such as trierucin and trilaurin, desired for industrial applications. Moreover, evidence has been provided that expression of acyltransferase genes in transgenic rapeseed plants can improve not only oil quality but also oil yield.