The distribution of caprylate, caprate and laurate in lipids from developing and mature seeds of transgenic Brassica napus L. |
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Authors: | Eva Wiberg Patricia Edwards James Byrne Sten Stymne Katayoon Dehesh |
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Institution: | (1) Calgene, 1920 Fifth Street, Davis, CA 95616, USA, US;(2) Department of Plant Biology, Swedish University of Agricultural Sciences, Box 7080, 75007 Uppsala, Sweden, SE;(3) Department of Plant Breeding, Swedish University of Agricultural Sciences, 26831 Svalšv, Sweden, SE |
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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.
Received: 11 February 2000 / Accepted: 2 May 2000 |
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Keywords: | :Brassica (transgenic) Diacylglycerol Medium chain fatty acid Phosphatidylcholine Triacylglycerol |
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