RADIOLABELING STUDIES OF ACYL LIPIDS IN DEVELOPING SEEDS OF BRASSICA-NAPUS .2. USE OF [2-H3]GLYCEROL PRECURSOR IN RADIOLABELING STUDIES OF ACYL LIPIDS IN DEVELOPING SEEDS OF BRASSICA-NAPUS

The incorporation of radioactivity from [2-H-3]glycerol into lipids was studied in embryos isolated from developing oilseed rape (Brassica napus cv Shiralee) seeds. Total incorporation was linear for up to 4 hr with high labelling of the diacylglycerol (DAG) fraction. Polar lipids (PLs) only accounted for about 25% of the total lipid radioactivity. With seed development, there were changes in the relative labelling of different lipid classes. In particular, within the PLs phosphatidylglycerol (PtdGly) was well labelled in tissues of intermediate development [28-33 days after pollination (DAP)] while phosphatidylcholine (PtdCho) and monoacyl(lyso)phosphatidylcholine (LysoPtdCho) showed reciprocal changes with each other as development proceeded. Changes in the relative labelling of triacylglycerols (TAGs) and DAGs in embryos of different ages, together with the high labelling of the latter, suggested that diacylglycerol acyltransferase (DAGAT) could exert significant flux control during periods of rapid lipid synthesis.