Rachel Million-Rousseau

Publications (3)8.48 Total impact

• Source

  Available from: Björn Hamberger

  Dataset: Cytochromes P450 in phenolic metabolism Ehlting et al (2006) Phytochem Rev

  Jürgen Ehlting, Björn Hamberger, Rachel Million-Rousseau, Danièle Werck-Reichhart
• Source

  Available from: Björn Hamberger

  Article: Cytochromes P450 in phenolic metabolism

  Jürgen Ehlting, Björn Hamberger, Rachel Million-Rousseau, Danièle Werck-Reichhart
  [show abstract] [hide abstract]
  ABSTRACT: Three independent cytochrome P450 enzyme families catalyze the three rate-limiting hydroxylation steps in the phenylpropanoid pathway leading to the biosynthesis of lignin and numerous other phenolic compounds in plants. Their characterization at the molecular and enzymatic level has revealed an unexpected complexity of phenolic metabolism as the major route involves shikimate/quinate esters and alcohol/aldehyde intermediates. Engineering expression of CYP73s (encoding cinnamate 4-hydroxylase), CYP98s (encoding 4-coumaroylshikimate 3′-hydroxylase) or CYP84s (encoding coniferaldehyde 5-hydroxylase) leads to modified lignin and seed phenolic composition. In particular CYP73s and CYP98s also play essential roles in plant growth and development, while CYP84 constitutes a check-point for the synthesis of syringyl lignin and sinapate esters. Although recent data shed new light on the main path for lignin synthesis, they also raised new questions. Mutants and engineered plants revealed the existence of (an) alternative pathway(s), which most likely involve(s) different precursors and oxygenases. On the other hand, phylogenetic analysis of plant genomes show the existence of P450 gene duplications in each family, which may have led to the acquisition of novel or additional physiological functions in planta. In addition to the main lignin pathway, P450s contribute to the biosynthesis of many bioactive phenolic derivatives, with potential applications in medicine and plant defense, including lignans, phenylethanoids, benzoic acids, xanthones or quinoid compounds. A very small proportion of these P450s have been characterized so far, and rarely at a molecular level. The possible involvement of P450s in salicylic acid is discussed.
  Phytochemistry Reviews 04/2012; 5(2):239-270. · 4.33 Impact Factor
• Source

  Available from: Alexandre de Kochko

  Article: Functional characterization of two p-coumaroyl ester 3'-hydroxylase genes from coffee tree: evidence of a candidate for chlorogenic acid biosynthesis.

  Venkataramaiah Mahesh, Rachel Million-Rousseau, Pascaline Ullmann, Nathalie Chabrillange, José Bustamante, Laurence Mondolot, Marc Morant, Michel Noirot, Serge Hamon, Alexandre de Kochko, Danièle Werck-Reichhart, Claudine Campa
  [show abstract] [hide abstract]
  ABSTRACT: Chlorogenic acid (5-CQA) is one of the major soluble phenolic compounds that is accumulated in coffee green beans. With other hydroxycinnamoyl quinic acids (HQAs), this compound is accumulated in particular in green beans of the cultivated species Coffea canephora. Recent work has indicated that the biosynthesis of 5-CQA can be catalyzed by a cytochrome P450 enzyme, CYP98A3 from Arabidopsis. Two full-length cDNA clones (CYP98A35 and CYP98A36) that encode putative p-coumaroylester 3'-hydroxylases (C3'H) were isolated from C. canephora cDNA libraries. Recombinant protein expression in yeast showed that both metabolized p-coumaroyl shikimate at similar rates, but that only one hydroxylates the chlorogenic acid precursor p-coumaroyl quinate. CYP98A35 appears to be the first C3'H capable of metabolising p-coumaroyl quinate and p-coumaroyl shikimate with the same efficiency. We studied the expression patterns of both genes on 4-month old C. canephora plants and found higher transcript levels in young and in highly vascularized organs for both genes. Gene expression and HQA content seemed to be correlated in these organs. Histolocalization and immunolocalization studies revealed similar tissue localization for caffeoyl quinic acids and p-coumaroylester 3'-hydroxylases. The results indicated that HQA biosynthesis and accumulation occurred mainly in the shoot tip and in the phloem of the vascular bundles. The lack of correlation between gene expression and HQA content observed in some organs is discussed in terms of transport and accumulation mechanisms.
  Plant Molecular Biology 06/2007; 64(1-2):145-59. · 4.15 Impact Factor