title: Identification of genes coding for functional zeaxanthin epoxidases in the diatom Phaeodactylum tricornutum.
abstract: Phaeodactylum tricornutum like other diatoms synthesizes fucoxanthin and diadinoxanthin as major carotenoid end products. The genes involved have recently been assigned for early pathway steps. Beyond β-carotene, only gene candidates for β-carotene hydroxylase, zeaxanthin epoxidase and zeaxanthin de-epoxidase have been proposed from the available genome sequence. The two latter enzymes may be involved in the two different xanthophyll cycles which operate in P. tricornutum. The function of three putative zeaxanthin epoxidase genes (zep) was addressed by pathway complementation in the Arabidopsis thaliana Zep mutant npq2. Genes zep2 and zep3 were able to restore zeaxanthin epoxidation and a functional xanthophyll cycle but the corresponding enzymes exhibited different catalytic activities. Zep3 functioned as a zeaxanthin epoxidase whereas Zep2 exhibited a broader substrate specificity additionally converting lutein to lutein-5,6-epoxide. Although zep1 was transcribed and the protein could be identified after import into the chloroplast in A. thaliana, Zep1 was found not to be functional in zeaxanthin epoxidation. The non-photochemical quenching kinetics of wild type A. thaliana was only restored in transformant npq2-zep3.
authors: Department of Molecular Bioscience, J.W. Goethe University, Max-v-Laue Str. 9, D-60438 Frankfurt, Germany.
authors: Ulrike
authors: U
authors: Eilers
authors: Department of Molecular Bioscience, J.W. Goethe University, Max-v-Laue Str. 9, D-60438 Frankfurt, Germany.
authors: Lars
authors: L
authors: Dietzel
authors: Department of Molecular Bioscience, J.W. Goethe University, Max-v-Laue Str. 9, D-60438 Frankfurt, Germany.
authors: Jürgen
authors: J
authors: Breitenbach
authors: Department of Molecular Bioscience, J.W. Goethe University, Max-v-Laue Str. 9, D-60438 Frankfurt, Germany.
authors: Claudia
authors: C
authors: Büchel
authors: Department of Molecular Bioscience, J.W. Goethe University, Max-v-Laue Str. 9, D-60438 Frankfurt, Germany. Electronic address: sandmann@bio.uni-frankfurt.de.
authors: Gerhard
authors: G
authors: Sandmann
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D002338:Carotenoids / Q000378:metabolism*; D017377:Diatoms / Q000201:enzymology* / Q000235:genetics; D005816:Genetic Complementation Test; D007700:Kinetics; D014975:Lutein / Q000031:analogs & derivatives / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D024341:Xanthophylls / Q000378:metabolism*; D065146:Zeaxanthins / Q000378:metabolism
chemical_list: D024341:Xanthophylls; D065146:Zeaxanthins; C523080:lutein-5,6-epoxide; C025164:fucoxanthin; C033808:diadinoxanthin; D002338:Carotenoids; D006899:Mixed Function Oxygenases; D010088:Oxidoreductases; C097153:zeaxanthin epoxidase; C079232:beta-carotene hydroxylase; D014975:Lutein
keywords: Arabidopsis thaliana npq2 mutant; Diatoms; Fucoxanthin synthesis; Phaeodactylum tricornutum; Xanthophyll cycle; Zeaxanthin epoxidase