title: Iridoid Synthase Activity Is Common among the Plant Progesterone 5β-Reductase Family.
abstract: Catharanthus roseus, the Madagascar periwinkle, synthesizes bioactive monoterpenoid indole alkaloids, among which the anti-cancer drugs vinblastine and vincristine. The monoterpenoid branch of the alkaloid pathway leads to the secoiridoid secologanin and involves the enzyme iridoid synthase (IS), a member of the progesterone 5β-reductase (P5βR) family. IS reduces 8-oxogeranial to iridodial. Through transcriptome mining, we show that IS belongs to a family of six C. roseus P5βR genes. Characterisation of recombinant CrP5βR proteins demonstrates that all but CrP5βR3 can reduce progesterone, and thus can be classified as P5βRs. Three of them, namely CrP5βR1, CrP5βR2 and CrP5βR4, could also reduce 8-oxogeranial, pointing to a possible redundancy with IS (corresponding to CrP5βR5) in secoiridoid synthesis. In depth functional analysis by subcellular protein localisation, gene expression analysis, in situ hybridisation and virus-induced gene silencing, indicates that besides IS, CrP5βR4 may also participate in secoiridoid biosynthesis. Finally, we cloned a set of P5βR genes from angiosperm plant species not known to produce iridoids and demonstrate that the corresponding recombinant proteins are also capable of using 8-oxogeranial as a substrate. This suggests that 'IS activity' is intrinsic to angiosperm P5βR proteins and has evolved early during evolution.
authors.affiliation: Department of Biology, University of Erlangen-Nuremberg, 91058 Erlangen, Germany.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Munkert
authors.affiliation: Department of Plant Systems Biology, VIB, 9052 Ghent, Belgium Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium.
authors.forename: Jacob
authors.initials: J
authors.lastname: Pollier
authors.affiliation: Sylvius Laboratory, Institute of Biology Leiden, Leiden University, Leiden 2333 BE, The Netherlands.
authors.forename: Karel
authors.initials: K
authors.lastname: Miettinen
authors.affiliation: Department of Plant Systems Biology, VIB, 9052 Ghent, Belgium Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium.
authors.forename: Alex
authors.initials: A
authors.lastname: Van Moerkercke
authors.affiliation: Department of Biological Chemistry, John Innes Centre, Norwich NR4 7UH, UK.
authors.forename: Richard
authors.initials: R
authors.lastname: Payne
authors.affiliation: Department of Biology, University of Erlangen-Nuremberg, 91058 Erlangen, Germany.
authors.forename: Frieder
authors.initials: F
authors.lastname: Müller-Uri
authors.affiliation: Université de Toulouse, UPS, UMR 5546, Laboratoire de Recherche en Sciences Végétales, BP 42617 Auzeville, F-31326 Castanet-Tolosan, France CNRS, UMR 5546, BP 42617, F-31326 Castanet-Tolosan, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Burlat
authors.affiliation: Department of Biological Chemistry, John Innes Centre, Norwich NR4 7UH, UK.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: O'Connor
authors.affiliation: Sylvius Laboratory, Institute of Biology Leiden, Leiden University, Leiden 2333 BE, The Netherlands.
authors.forename: Johan
authors.initials: J
authors.lastname: Memelink
authors.affiliation: Department of Biology, University of Erlangen-Nuremberg, 91058 Erlangen, Germany wolfgang.kreis@fau.de.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Kreis
authors.affiliation: Department of Plant Systems Biology, VIB, 9052 Ghent, Belgium Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium alain.goossens@psb.vib-ugent.be.
authors.forename: Alain
authors.initials: A
authors.lastname: Goossens
keywords: Catharanthus roseus; Erysimum crepidifolium; Madagascar periwinkle; Medicago truncatula; VEP1-encoded enone-reductases; monoterpenoid indole alkaloid; progesterone reductase; secoiridoid