Distribution of lipid radioactivity after fractionation of C-14-labelled zygotic rape embryos

In developing green rape embryos isolated from oilseed rape (Brassica napus L. cv. Nilla) lipid synthesis from [C-14]bicarbonate, [1-C-14]acetate and [U-C-14]glycerol was significantly driven by light. In contrast to erucate-free varieties the embryos of this erucate-rich variety showed enhanced triacylglycerol formation, caused primarily by incorporation of erucate into diacylglycerol. After fractionation of labelled embryos the products of triacylglycerol formation with very long chain fairy acids accumulated in the oil body-enriched fat pad. The low incorporation rates into very long chain fatty acids and triacylglycerols remaining in the microsomal fraction correspond to elongation activities and triacylglycerol synthesizing capacities of microsomes in vitro. Together with recent findings in other laboratories these results suggest an intimate association of oil bodies with domains of the endoplasmic reticulum, which are Involved in the synthesis of storage lipids.