A MUTANT OF ARABIDOPSIS DEFICIENT IN THE ELONGATION OF PALMITIC ACID

The overall fatty acid composition of leaf lipids in a mutant of Arabi dopsis thaliana was characterized by an increased level of 16:0 and a concomitant decrease of 18-carbon fatty acids as a consequence of a si ngle recessive nuclear mutation at the fab1 locus. Quantitative analys is of the fatty acid composition of individual lipids established that lipids synthesized by both the prokaryotic and eukaryotic pathways we re affected by the mutation. Direct enzyme assays demonstrated that th e mutant plants were deficient in the activity of 3-ketoacyl-acyl carr ier protein synthase II; therefore, it is inferred that fabl may encod e this enzyme. Labeling experiments with [C-14]acetate and lipase posi tional analysis indicated that the mutation results in a small shift i n the partitioning of lipid synthesis between the prokaryotic and euka ryotic pathways. Synthesis of chloroplast lipids by the prokaryotic pa thway was increased with a corresponding reduction in the eukaryotic p athway.