Mutations in the fatty acid elongation 1 gene are associated with a loss of beta-ketoacyl-CoA synthase activity in low erucic acid rapeseed

Low erucic acid rapeseed (LEAR) is characterised by a near absence of very long chain fatty acids in the seed oil which has been correlated with a lac k of acyl-CoA elongation activity. Here we show that the absence of acyl-Co A and ATP-dependent elongation activities in microsomes isolated from LEAR embryos is associated with an absence of beta -ketoacyl-CoA synthase activi ty encoded by the Bn-fatty acid elongation 1 (FAE1) genes. Size exclusion c hromatography of solubilised microsomes revealed the presence of a high mol ecular mass acyl-CoA elongase complex in high erucic acid rapeseed which wa s absent in microsomes isolated from LEAR seeds. Although transcripts for t he Bn-FAE1 genes were detected in LEAR embryos, immunoblots using antisera raised against the beta -ketoacyl-CoA synthase indicated an absence of this protein, Comparison of the deduced amino acid sequences of immature embryo cDNAs reveals that LEAR alleles of Bn-FAE1 encode variant beta -ketoacyl-C oA synthase proteins. (C) 2001 Federation of European Biochemical Societies , Published by Elsevier Science B.V. All rights reserved.