PLANT PHYSIOLOGY , Vol 114, Issue 1 63-68, Copyright © 1997 by American Society of Plant Biologists
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BIOCHEMISTRY AND ENZYMOLOGY |
Metabolism of Hydroxy Fatty Acids in Developing Seeds in the Genera Lesquerella (Brassicaceae) and Linum (Linaceae)
D. W. Reed, D. C. Taylor and P. S. Covello
National Research Council, Plant Biotechnology Institute, 110 Gymnasium Place, Saskatoon, Saskatchewan, Canada S7N 0W9
Members of the genus Lesquerella produce seed oil that contains a high
proportion of hydroxy fatty acids (HFAs). There are three groups of
Lesquerella species that are distinguished by their most abundant seed oil
fatty acid: lesquerolic acid (20:1OH; e.g. Lesquerella fendleri),
densipolic acid (18:2OH; e.g. Lesquerella kathryn), and auricolic acid
(20:2OH; e.g. Lesquerella auriculata). To investigate the biochemistry of
HFA production in Lesquerella species, the conversion of putative
radiolabeled intermediates of HFA biosynthesis, including 18:1,
20:1,18:1OH, 18:2OH, and 20:1OH, was examined in developing embryos of L.
fendleri, L.kathryn, and L. auriculata. The results are consistent with (a)
18:1OH formation by hydroxylation of 18:1, (b) elongation and desaturation
of 18:1OH to produce 20:1OH and 18:2OH, respectively, and (c) desaturation
of 20:1OH to produce 20:2OH. The desaturation of 20:1OH was also found to
occur in developing embryos of high, but not low, linolenic acid flax. This
suggests that the desaturation is catalyzed by the extraplastidial
linoleate desaturase. Confirming this suggestion, it was notable that
18:1OH and 18:2OH were found in low and high linolenic flax (Linum
usitatissimum) seeds, respectively, at levels of 0.2 to 1%.
