PLANT PHYSIOLOGY , Vol 106, Issue 1 143-150, Copyright © 1994 by American Society of Plant Biologists
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METABOLISM AND ENZYMOLOGY |
A Mutant of Arabidopsis Deficient in the Elongation of Palmitic Acid
J. Wu, D. W. James Jr, H. K. Dooner and J. Browse
Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164-6340 (J.W., J.B.)
The overall fatty acid composition of leaf lipids in a mutant of
Arabidopsis thaliana was characterized by an increased level of 16:0 and a
concomitant decrease of 18-carbon fatty acids as a consequence of a single
recessive nuclear mutation at the fab1 locus. Quantitative analysis of the
fatty acid composition of individual lipids established that lipids
synthesized by both the prokaryotic and eukaryotic pathways were affected
by the mutation. Direct enzyme assays demonstrated that the mutant plants
were deficient in the activity of 3-ketoacyl-acyl carrier protein synthase
II; therefore, it is inferred that fab1 may encode this enzyme. Labeling
experiments with [14C]acetate and lipase positional analysis indicated that
the mutation results in a small shift in the partitioning of lipid
synthesis between the prokaryotic and eukaryotic pathways. Synthesis of
chloroplast lipids by the prokaryotic pathway was increased with a
corresponding reduction in the eukaryotic pathway.
