MODIFICATION OF SEED OIL CONTENT AND ACYL COMPOSITION IN THE BRASSICACEAE BY EXPRESSION OF A YEAST SN-2 ACYLTRANSFERASE GENE

A putative yeast sn-2 acyltransferase gene (SLC1-1), reportedly a vari ant acyltransferase that suppresses a genetic defect in sphingolipid l ong-chain base biosynthesis, has been expressed in a yeast SLC deletio n strain. The SLC1-1 gene product was shown in vitro to encode an sn-2 acyltransferase capable of acylating sn-l oleoyl-lysophosphatidic aci d, using a range of acyl-CoA thioesters, including 18:1-, 22:1-, and 2 4:0-CoAs. The SLC1-1 gene was introduced into Arabidopsis and a high e rucic acid-containing Brassica napus cv Hero under the control of a co nstitutive (tandem cauliflower mosaic virus 35S) promoter. The resulti ng transgenic plants showed substantial increases of 8 to 48% in seed oil content (expressed on the basis of seed dry weight) and increases in both overall proportions and amounts of very-long-chain fatty acids in seed triacylglycerols (TAGs). Furthermore, the proportion of very- long-chain fatty acids found at the sn-2 position of TAGs was increase d, and homogenates prepared from developing seeds of transformed plant s exhibited elevated lysophosphatidic acid acyltransferase (EC 2.3.1.5 1) activity. Thus, the yeast sn-2 acyltransferase has been shown to en code a protein that can exhibit lysophosphatidic acid acyltransferase activity and that can be used to change total fatty acid content and c omposition as well as to alter the stereospecific acyl distribution of fatty acids in seed TAGs.