Cloning and functional characterisation of an enzyme involved in the elongation of Delta6-polyunsaturated fatty acids from the moss Physcomitrella patens.
The moss Physcomitrella patens contains high proportions of polyunsaturated very-long-chain fatty acids with up to 20 carbon atoms. Starting from preformed C18 polyunsaturated fatty acids, their biosynthesis involves a sequence of Delta6-desaturation, Delta6-elongation and Delta5-desaturation. In this report we describe for the first time the characterisation of a cDNA (PSE1) of plant origin with homology to the ELO-genes from Saccharomyces cerevisiae, encoding a component of the Delta6-elongase. Functional expression of PSE1 in S. cerevisiae led to the elongation of exogenously supplied Delta6-polyunsaturated fatty acids. By feeding experiments with different trienoic fatty acids of natural and synthetic origin, both substrate specificity and substrate selectivity of the enzyme were investigated. The activity of Pse1, when expressed in yeast, was not sensitive to the antibiotic cerulenin, which is an effective inhibitor of fatty acid synthesis and elongation. Furthermore, the PSE1 gene was disrupted in the moss by homologous recombination. This led to a complete loss of all C20 polyunsaturated fatty acids providing additional evidence for the function of the cDNA as coding for a component of the Delta6-elongase. The elimination of the elongase was not accompanied by a visible alteration in the phenotype, indicating that C20-PUFAs are not essential for viability of the moss under phytotron conditions.
Zank
Thorsten K
TK
Universität Hamburg, Institut für Allgemeine Botanik, Ohnhorststrasse 18, 22609 Hamburg, Germany. fb8a001@botanik.uni-hamburg.de
Zähringer
Ulrich
U
Beckmann
Christoph
C
Pohnert
Georg
G
Boland
Wilhelm
W
Holtorf
Hauke
H
Reski
Ralf
R
Lerchl
Jens
J
Heinz
Ernst
E
D000595:Amino Acid Sequence; D019068:Bryopsida / Q000201:enzymology* / Q000235:genetics*; D005231:Fatty Acids, Unsaturated / Q000096:biosynthesis*; D017343:Genes, Plant / Q000235:genetics*; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D011995:Recombination, Genetic / Q000235:genetics; D012441:Saccharomyces cerevisiae; D017385:Sequence Homology; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D005231:Fatty Acids, Unsaturated; D010940:Plant Proteins