As a prelude to detailed flux control analysis of lipid synthesis in plants, we have examined the latter in tissue cultures from two important oil crops, olive (Olea europaea L.) and oil palm (Elaeis guineensis Jacq.). Temperature was used to manipulate the overall rate of lipid formation in order to characterize and validate the system to be used for analysis. With [1-14C]acetate as a precursor, an increase in temperature from 20 to 30°C produced nearly a doubling of total lipid labelling. This increase in total lipids did not change the radioactivity in the intermediate acyl-(acyl carrier protein) or acyl-CoA pools, indicating that metabolism of these pools did not exert any significant constraint for overall synthesis. In contrast, there were some differences in the proportional labelling of fatty acids and of lipid classes at the two temperatures. The higher temperature caused a decrease in polyunsaturated fatty acid labelling and an increase in the proportion of triacylglycerol labelling in both calli. The intermediate diacylglycerol was increased in olive, but not in oil palm. Overall the data indicate the suitability of olive and oil-palm cultures for the study of lipid synthesis and indicate that de novo fatty acid synthesis may exert more flux control than complex lipid assembly. In olive, diacylglycerol acyltransferase may exert significant flux control when lipid synthesis is rapid.
- fatty acid biosynthesis
- lipid accumulation
- metabolic control
- oil fruit
↵1 Present address: Malaysian Palm Oil Board, P.O. Box 10620, 50720 Kuala Lumpur, Malaysia.
↵2 Present address: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K.
Abbreviations used: DAG, diacylglycerol; TAG, triacylglycerol; NEFA, non-esterified fatty acid; PtdCho, phosphatidylcholine; PtdEtn, phosphatidylethanolamine; PtdOH, phosphatidic acid; ACP, acyl carrier protein; FAME, fatty acid methyl ester; KAS, β-ketoacyl-ACP synthase (β-oxoacyl-ACP synthase); TDCA, Top-Down Control Analysis.
- The Biochemical Society, London ©2002