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 wa s studied in embryos isolated from developing oilseed rape (Brassica n apus cv Shiralee) seeds. Total incorporation was linear for up to 4 hr with high labelling of the diacylglycerol (DAG) fraction. Polar lipid s (PLs) only accounted for about 25% of the total lipid radioactivity. With seed development, there were changes in the relative labelling o f different lipid classes. In particular, within the PLs phosphatidylg lycerol (PtdGly) was well labelled in tissues of intermediate developm ent [28-33 days after pollination (DAP)] while phosphatidylcholine (Pt dCho) and monoacyl(lyso)phosphatidylcholine (LysoPtdCho) showed recipr ocal changes with each other as development proceeded. Changes in the relative labelling of triacylglycerols (TAGs) and DAGs in embryos of d ifferent ages, together with the high labelling of the latter, suggest ed that diacylglycerol acyltransferase (DAGAT) could exert significant flux control during periods of rapid lipid synthesis.