Identification of a gene that complements an Arabidopsis mutant deficient in chloroplast omega 6 desaturase activity.
Membrane lipids of the fad6 (formerly fadC) mutant of Arabidopsis, which is deficient in chloroplast omega 6 desaturase activity, have increased levels of monounsaturated fatty acids and are deficient in trienoic fatty acids. A putative fad6 cDNA clone was isolated by probing a cDNA library with a degenerate oligonucleotide based on a conserved region within known omega 3 desaturase genes. Expression of the cDNA in transgenic plants of a fad6 mutant restored normal levels of all fatty acids. When used as a hybridization probe, the cDNA identified a restriction fragment-length polymorphism that co-segregated with the fad6 mutation. Thus, on the basis of a genetic complementation test and genetic map position, the fad6 gene is encoded by the cDNA. The cDNA encoded a 418-amino acid polypeptide of 47,727 D that displayed a high degree of sequence similarity to a delta 12 desaturase from the cyanobacterium Synechocystis. The fad6 gene exhibited less sequence homology to any known higher plant desaturase, including an endoplasmic reticulum-localized omega 6 desaturase corresponding to the Arabidopsis fad2 gene.
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Carnegie Institution, Department of Plant Biology, Stanford, California 94305.
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Lemieux
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Somerville
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D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics*; D015152:Blotting, Northern; D002736:Chloroplasts / Q000201:enzymology*; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D044943:Fatty Acid Desaturases / Q000235:genetics* / Q000378:metabolism; D017353:Gene Deletion; D015723:Gene Library; D017343:Genes, Plant; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D009154:Mutation; D012150:Polymorphism, Restriction Fragment Length; D018749:RNA, Plant / Q000096:biosynthesis / Q000302:isolation & purification; D017386:Sequence Homology, Amino Acid
D018749:RNA, Plant; D044943:Fatty Acid Desaturases; C040448:delta-12 fatty acid desaturase