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Iridoid synthase activity is common among the plant progesterone 5β-reductase family

  • Jennifer Munkert
  • Jacob Pollier
  • Karel Miettinen
  • Alex Van Moerkercke
  • Richard J. Payne
  • Frieder Müller-Uri
  • Vincent Burlat
  • Sarah E O'Connor
  • Johan Memelink
  • Wolfgang Kreis
  • Alain Goossens
Publishing year: 2015-01
Language: English
Pages: 136-152
Publication/Series: Molecular Plant
Volume: 8
Issue: 1
Document type: Journal article
Publisher: Oxford University Press

Abstract english

Catharanthus roseus, the Madagascar periwinkle, synthesizes bioactive monoterpenoid indole alkaloids, including 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. Characterization 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, can also reduce 8-oxogeranial, pointing to a possible redundancy with IS (corresponding to CrP5βR5) in secoiridoid synthesis. In-depth functional analysis by subcellular protein localization, gene expression analysis, in situ hybridization, and virus-induced gene silencing indicate that besides IS, CrP5βR4 may also participate in secoiridoid biosynthesis. 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.


  • Biochemistry and Molecular Biology
  • Catharanthus
  • Gene Expression Regulation, Plant
  • Iridoids
  • Molecular Sequence Data
  • Plant Proteins
  • Progesterone Reductase
  • Journal Article
  • Research Support, Non-U.S. Gov't


  • ISSN: 1752-9867
Alex Van Moerkercke
E-mail: alex [dot] van_moerkercke [at] biol [dot] lu [dot] se

Postdoctoral fellow

Molecular Cell Biology

+46 46 222 49 49


Sölvegatan 35, Lund


Research group

Plant Biology



Postdoc host

Olivier Van Aken