title: Identification and functional characterization of the moss Physcomitrella patens delta5-desaturase gene involved in arachidonic and eicosapentaenoic acid biosynthesis.
abstract: The moss Physcomitrella patens contains high levels of arachidonic acid and lesser amounts of eicosapentaenoic acid. Here we report the identification and characterization of a delta5-desaturase from P. patens that is associated with the synthesis of these fatty acids. A full-length cDNA for this desaturase was identified by data base searches based on homology to sequences of known delta5-desaturase cDNAs from fungal and algal species. The resulting P. patens cDNA encodes a 480-amino acid polypeptide that contains a predicted N-terminal cytochrome b5-like domain as well as three histidine-rich domains. Expression of the enzyme in Saccharomyces cerevisiae resulted in the production of the delta5-containing fatty acid arachidonic acid in cells that were provided di-homo-gamma-linolenic acid. In addition, the expressed enzyme generated delta5-desaturation products with the C20 substrates omega-6 eicosadienoic and omega-3 eicosatrienoic acids, but no products were detected with the C18 fatty acid linoleic and alpha-linolenic acids or with the C22 fatty acid adrenic and docosapentaenoic acids. When the corresponding P. patens genomic sequence was disrupted by replacement through homologous recombination, a dramatic alteration in the fatty acid composition was observed, i.e. an increase in di-homo-gamma-linolenic and eicosatetraenoic acids accompanied by a concomitant disappearance of the delta5-fatty acid arachidonic and eicosapentaenoic acids. In addition, overexpression of the P. patens cDNA in protoplasts isolated from a disrupted line resulted in the restoration of arachidonic acid synthesis.
authors.affiliation: Department of Pharmacognosy, Mahidol University, 447 Sri-Ayudhya Road, Ratchathewi, Bangkok 10400, Thailand.
authors.forename: Songsri
authors.initials: S
authors.lastname: Kaewsuwan
authors.affiliation: United States Department of Agriculture Agricultural Research Service, Plant Genetics Research Unit, Donald Danforth Plant Science Center, St. Louis, Missouri 63132.
authors.forename: Edgar B
authors.initials: EB
authors.lastname: Cahoon
authors.affiliation: Department of Biology, Washington University in St. Louis, S Louis, Missouri 63130-4899.
authors.forename: Pierre-François
authors.initials: PF
authors.lastname: Perroud
authors.affiliation: Department of Microbiology, Faculty of Pharmacy, Mahidol University, 447 Sri-Ayudhya Road, Ratchathewi, Bangkok 10400, Thailand.
authors.forename: Chanpen
authors.initials: C
authors.lastname: Wiwat
authors.affiliation: Department of Plant Sciences, Faculty of Sciences, Mahidol University, Rama VI Road, Bangkok 10400, Thailand.
authors.forename: Nathinee
authors.initials: N
authors.lastname: Panvisavas
authors.affiliation: Department of Biology, Washington University in St. Louis, S Louis, Missouri 63130-4899. Electronic address: rsq@biology.wustl.edu.
authors.forename: Ralph S
authors.initials: RS
authors.lastname: Quatrano
authors.affiliation: Department of Biology, Washington University in St. Louis, S Louis, Missouri 63130-4899.
authors.forename: David J
authors.initials: DJ
authors.lastname: Cove
authors.affiliation: Department of Pharmacognosy, Mahidol University, 447 Sri-Ayudhya Road, Ratchathewi, Bangkok 10400, Thailand. Electronic address: pynby@mahidol.ac.th.
authors.forename: Nuntavan
authors.initials: N
authors.lastname: Bunyapraphatsara
mesh_terms: D016718:Arachidonic Acid / Q000096:biosynthesis*; D044002:Bryophyta; D019068:Bryopsida / Q000201:enzymology*; D003001:Cloning, Molecular; D018076:DNA, Complementary; D000090943:Delta-5 Fatty Acid Desaturase; D004537:Eicosanoic Acids; D015118:Eicosapentaenoic Acid / Q000096:biosynthesis*; D044943:Fatty Acid Desaturases / Q000235:genetics*; D010940:Plant Proteins / Q000235:genetics; D011523:Protoplasts / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D000090943:Delta-5 Fatty Acid Desaturase; D004537:Eicosanoic Acids; D010940:Plant Proteins; D016718:Arachidonic Acid; D015118:Eicosapentaenoic Acid; D044943:Fatty Acid Desaturases