title: The Woody-Preferential GeneEgMYB88Regulates the Biosynthesis of Phenylpropanoid-Derived Compounds in Wood.
abstract: Comparative phylogenetic analyses of the R2R3-MYB transcription factor family revealed that five subgroups were preferentially found in woody species and were totally absent from Brassicaceae and monocots (Soler et al., 2015). Here, we analyzed one of these subgroups (WPS-I) for which no gene had been yet characterized. MostEucalyptusmembers of WPS-I are preferentially expressed in the vascular cambium, the secondary meristem responsible for tree radial growth. We focused onEgMYB88, which is the most specifically and highly expressed in vascular tissues, and showed that it behaves as a transcriptional activator in yeast. Then, we functionally characterizedEgMYB88in both transgenicArabidopsisand poplar plants overexpressing either the native or the dominant repression form (fused to the Ethylene-responsive element binding factor-associated Amphiphilic Repression motif, EAR). The transgenicArabidopsislines had no phenotype whereas the poplar lines overexpressingEgMYB88exhibited a substantial increase in the levels of the flavonoid catechin and of some salicinoid phenolic glycosides (salicortin, salireposide, and tremulacin), in agreement with the increase of the transcript levels of landmark biosynthetic genes. A change in the lignin structure (increase in the syringyl vs. guaiacyl, S/G ratio) was also observed. Poplar lines overexpressing theEgMYB88dominant repression form did not show a strict opposite phenotype. The level of catechin was reduced, but the levels of the salicinoid phenolic glycosides and the S/G ratio remained unchanged. In addition, they showed a reduction in soluble oligolignols containing sinapylp-hydroxybenzoate accompanied by a mild reduction of the insoluble lignin content. Altogether, these results suggest thatEgMYB88, and more largely members of the WPS-I group, could control in cambium and in the first layers of differentiating xylem the biosynthesis of some phenylpropanoid-derived secondary metabolites including lignin.
authors.affiliation: Laboratoire de Recherche en Sciences Végétales, Centre National de la Recherche Scientifique, Université de Toulouse III, Paul Sabatier Toulouse, France.
authors.forename: Marçal
authors.initials: M
authors.lastname: Soler
authors.affiliation: Laboratoire de Recherche en Sciences Végétales, Centre National de la Recherche Scientifique, Université de Toulouse III, Paul Sabatier Toulouse, France.
authors.forename: Anna
authors.initials: A
authors.lastname: Plasencia
authors.affiliation: Laboratoire de Recherche en Sciences Végétales, Centre National de la Recherche Scientifique, Université de Toulouse III, Paul Sabatier Toulouse, France.
authors.forename: Jorge
authors.initials: J
authors.lastname: Lepikson-Neto
authors.affiliation: Laboratoire de Recherche en Sciences Végétales, Centre National de la Recherche Scientifique, Université de Toulouse III, Paul Sabatier Toulouse, France.
authors.forename: Eduardo L O
authors.initials: EL
authors.lastname: Camargo
authors.affiliation: Laboratoire de Recherche en Sciences Végétales, Centre National de la Recherche Scientifique, Université de Toulouse III, Paul Sabatier Toulouse, France.
authors.forename: Annabelle
authors.initials: A
authors.lastname: Dupas
authors.affiliation: Laboratoire de Recherche en Sciences Végétales, Centre National de la Recherche Scientifique, Université de Toulouse III, Paul Sabatier Toulouse, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Ladouce
authors.affiliation: Department of Plant Physiology, Umeå University Umeå, Sweden.
authors.forename: Edouard
authors.initials: E
authors.lastname: Pesquet
authors.affiliation: Laboratoire de Recherche en Sciences Végétales, Centre National de la Recherche Scientifique, Université de Toulouse III, Paul Sabatier Toulouse, France.
authors.forename: Fabien
authors.initials: F
authors.lastname: Mounet
authors.affiliation: "Agronomie et Environnement" Nancy-Colmar, Institut National de la Recherche Agronomique, Université de Lorraine UMR1121 Vandœuvre-lès-Nancy, France.
authors.forename: Romain
authors.initials: R
authors.lastname: Larbat
authors.affiliation: Laboratoire de Recherche en Sciences Végétales, Centre National de la Recherche Scientifique, Université de Toulouse III, Paul Sabatier Toulouse, France.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Grima-Pettenati
keywords: Eucalyptus; MYB transcription factors; flavonoids; lignin; oligolignols; phenylpropanoid metabolism; salicinoid phenolic glycosides; vascular cambium