Changes in Lipid Composition during Callus Differentiation in Cultures of Oilseed Rape (Brassica napus L.)

The lipid composition of different callus cultures of Brassicanapus varied according to their state of differentiation. Photomixotrophiccallus was characterized by the ability to synthesize relativelyhigh levels of triacylglycerol (TAG) which was rich in oleate.Glycosyldiacylglycerols were also detected. In contrast, heterotrophiccallus was found to possess high proportions of membraneousphospholipids which were rich in palmitate, linoleate, and linolenate.Moreover, the lipid content was considerably less than thatof photomixotrophic callus. Caulogenesis was achieved in bothtypes of callus strains and the lipid composition of the regeneratedleaves contained a much higher proportion of chloroplast glycosyldiacylglycerolsand thus resembled more those of the parent plant. Some callientered a senescent phase whereby there was considerable degradationof the constituent membrane lipids. Senescent callus also exhibiteda high proportion of polyploid nuclei. In this study we havebeen able to cause large changes in the morphology of calluscultures. These morphological changes were accompanied by significantalterations in the quality and quantity of acyl lipids. In photomixotrophiccells the lipid changes resembled those seen for developingseed tissues where high rates of TAG deposition are accompaniedby an altered fatty acid pattern. Thus, the selection of differentcallus types should be of use for investigations of the regulationof lipid biosynthesis under controlled culture conditions.