A RAPESEED FAE1 GENE IS LINKED TO THE E1 LOCUS ASSOCIATED WITH VARIATION IN THE CONTENT OF ERUCIC-ACID

The synthesis of very long chain fatty acids occurs in the cytoplasm v ia an elongase complex. A key component of this complex is the beta-ke toacyl-CoA synthase, a condensing enzyme which in Arabidopsis is encod ed by the FAE1 gene. Two sequences homologous to the FAE1 gene were is olated from a Brassica napus immature embryo cDNA library. The two clo nes, CE7 and CE8, contain inserts of 1647 bp and 1654 bp, respectively . The CE7 gene encodes a protein of 506 amino acids and the CE8 clone, a protein of 505 amino acids, each having an approximate molecular ma ss of 56 kDa. The sequences of the two cDNA clones are highly homologo us yet distinct, sharing 97% nucleotide identity and 98% identity at t he amino acid level. Southern hybridisation showed the rapeseed beta-k etoacyl-CoA synthase to be encoded by a small multigene family. Northe rn hybridisation showed the expression of the rapeseed FAE1 gene(s) to be restricted to the immature embryo. One of the FAE1 genes is tightl y linked to the E1 locus, one of two loci controlling erucic acid cont ent in rapeseed. The identity of the second locus, E2, is discussed.