Directed Tagging of the Arabidopsis FATTY ACID

The FATTYAClD ELONGATlONl (FAEl) gene of Arabidopsis is required for the synthesis of very long chain fatty acids in the seed. The product of the FAEl gene is presumed to be a condensing enzyme that extends the chain length of fatty acids from C18 to C20 and C22. We report here the cloning of FAE7 by directed transposon tagging with the maire element Activator (Ac). An unstable fael mutant was isolated in a line carrying Ac linked to the FAEl locus on chromosome 4. Cosegregation and reversion analyses established that the new mutant was tagged by Ac. A DNA fragment flanking Ac was cloned by inverse polymerase chain reaction and used to isolate FAEl genomic clones and a cDNA clone from a library made from immature siliques. The predicted amino acid sequence of the FAEl protein shares homology with those of other condensing enzymes (chalcone synthase, stilbene synthases, and p-ketoacyl-acyl carrier protein synthase lll), supporting the notion that FAE7 is the structural gene for a synthase or condensing enzyme. FAEl is expressed in developing seed, but not in leaves, as expected from the effect of the fael mutation on the fatty acid compositions of those tissues.