title: The distribution of caprylate, caprate and laurate in lipids from developing and mature seeds of transgenic Brassica napus L.
abstract: The composition and positional distribution of lipids in developing and mature transgenic Brassica napus seeds accumulating up to 7 mol% of caprylate (8:0), 29 mol% caprate (10:0) or 63 mol% of laurate (12:0) were examined. The accumulation of 8:0 and 10:0 resulted from over-expression of the medium-chain-specific thioesterase (Ch FatB2) alone or together with the respective chain-length-specific condensing enzyme (Ch KASIV). Seeds containing high levels of 12:0 were obtained from plants expressing bay thioesterase (BTE) alone or crossed with a line over-expressing the coconut lysophosphatidic acid acyltransferase (LPAAT), an enzyme responsible for the increase in acylation of 12:0 at the sn-2 position. In all instances, 10:0 and 12:0 fatty acids were present in substantial amounts in phosphatidylcholine during seed development with a drastic decrease of 80-90% in mature seeds. At all stages of seed development however, 8:0 was barely detectable in this membrane lipid. Altogether, these results indicate that these transgenic seeds exclude and/or remove the medium-chain fatty acids from their membrane and that this mechanism(s) is more effective with the shorter-chain fatty acids. Furthermore, seeds of 8:0- and 10:0-producing lines had only negligible levels of these fatty acids present in the sn-2 position of the triacylglycerols. In contrast, all 12:0-producing seeds had a substantial amount of this fatty acid in the sn-2 position of the triacylglycerols, suggesting that the endogenous LPAAT is able to acylate 12:0 if no other acyl-CoA species are available.
authors.affiliation: Calgene, Davis, CA 95616, USA.
authors.forename: E
authors.initials: E
authors.lastname: Wiberg
authors.forename: P
authors.initials: P
authors.lastname: Edwards
authors.forename: J
authors.initials: J
authors.lastname: Byrne
authors.forename: S
authors.initials: S
authors.lastname: Stymne
authors.forename: K
authors.initials: K
authors.lastname: Dehesh
mesh_terms: D001937:Brassica / Q000378:metabolism*; D002210:Caprylates / Q000378:metabolism*; D003652:Decanoic Acids / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism; D007850:Lauric Acids / Q000378:metabolism*; D050356:Lipid Metabolism; D030821:Plants, Genetically Modified; D012639:Seeds / Q000378:metabolism
chemical_list: D002210:Caprylates; D003652:Decanoic Acids; D005227:Fatty Acids; D007850:Lauric Acids; C030358:lauric acid; C031071:decanoic acid; C031492:octanoic acid