Plant and Cell Physiology Advance Access published online on November 2, 2005
Plant and Cell Physiology, doi:10.1093/pcp/pci224
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1 Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan
* To whom correspondence should be addressed. Pinolenic acid (PA, 18:3
Received August 12, 2005
Accepted October 27, 2005
Regular Paper
A Front-End Desaturase from Chlamydomonas reinhardtii Produces Pinolenic and Coniferonic Acids by
13 Desaturation in Methylotrophic Yeast and Tobacco
2 Institute for Fundamental Research, Suntory Limited, Osaka 618-8503, Japan
3 Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan
Hideya Fukuzawa, E-mail: fukuzawa{at}lif.kyoto-u.ac.jp
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Abstract
5,9,12) and coniferonic acid (CA, 18:4
5,9,12,15) are
5-unsaturated bis-methylene-interrupted fatty acids (
5-UBIFAs) commonly found in pine seed oil. They are assumed to be synthesized from linoleic acid (LA, 18:2
9,12) and
-linolenic acid (ALA, 18:3
9,12,15) by
5-desaturation, respectively. A unicellular green microalga Chlamydomonas reinhardtii also accumulates PA and CA in a betain lipid. The EST resource of C. reinhardtii led to the isolation of a cDNA clone that encoded a putative fatty acid desaturase named as CrDES containing a cytochrome b5 domain at the N-terminus. When the coding sequence was expressed heterologously in the methylotrophic yeast Pichia pastoris, PA and CA were newly detected and the comparable amounts of LA and ALA were reduced, demonstrating that CrDES has
5-desaturase activity for both LA and ALA. CrDES expressed in the yeast showed
5-desaturase activity on 18:1
9 but not 18:1
11. Unexpectedly, CrDES also showed
7-desaturase activity on 20:2
11,14 and 20:3
11,14,17 to produce 20:3
7,11,14 and 20:4
7,11,14,17, respectively. Since both the
5 bond in C18 and the
7 bond in C20 fatty acids are "
13" double bonds, these results indicate that CrDES has
13 desaturase activity for
9 unsaturated C18/C20 fatty acids, in contrast to the previously reported front-end desaturases. In order to evaluate the activity of CrDES in higher plants, transgenic tobacco plants expressing CrDES were created. PA and CA accumulated in the leaves of transgenic plants. The highest combined yield of PA and CA was 44.7% of total fatty acids, suggesting that PA and CA can be produced in higher plants on a large scale.
5-unsaturated bis-methylene-interrupted fatty acids; fatty acid desaturase; Pichia pastoris; tobacco plant.
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