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Accueil du site > Equipes de recherche > Génomique fonctionnelle de l’Eucalyptus > Thèmes de recherche > Régulation transcriptionnelle de la formation de la paroi secondaire > Towards the identification of transcriptional complexes involved in the regulation of secondary cell wall formation in Eucalyptus

Towards the identification of transcriptional complexes involved in the regulation of secondary cell wall formation in Eucalyptus

By using promoter deletion analysis and in vivo foot-printing of the promoters of two genes specific of the lignin pathway (EgCAD2 and EgCCR), we have shown that the conserved MYB elements in these promoters are crucial for the formation of DNA-multiprotein complexes and for their transcriptional activation in vascular tissues. Thus MYB TFs play a central role in the transcriptional mechanisms by which lignin-specific pathway genes are coordinately expressed in vascular tissues [Rahantamalala et al. 2010]. We have characterized EgMYB1, a R2R3-MYB TF, preferentially expressed in Eucalyptus xylem, by overexpressing it in Poplar and Arabidopsis [Legay et al. 2010]. This was the first evidence of a master repressor able to regulate the biosynthesis of the three main polymers of SCW (lignin, cellulose and hemicellulose). Because protein-protein interaction is a major mechanism regulating the activity of TFs, we seeked for the protein partners of EgMYB1. We first constructed a yeast-two-hybrid library from Eucalyptus xylem and we screened it with EgMYB1. Among the candidate proteins able to interact with EgMYB1, we selected one histone linker (HisL) and one member of the OVATE TF family. We validated these interactions in planta using Förster Resonance Energy Transfer-Fluorescence Imaging Lifetime Microscopy (FRET-FLIM) (collaboration with the Imaging Platform of FR AIB). To evaluate the effects of these interactions on the formation of the SCW, we generated Arabidopsis transgenic plants overexpressing EgMYB1, EgHisL or EgOVATE alone, and lines overexpressing EgMYB1 + EgHisL and EgMYB1 + OVATE, respectively. EgHisL-OE and EgOVATE-OE plants were not significantly different from WT, whereas double transgenic lines EgMYB1 + EgHisL exhibited a much stronger phenotype than EgMYB1OE plants and the EgMYB1+ EgOVATE plants showed a restoration of the WT phenotype. These lines are currently analyzed using transcriptomic, histology and biochemical approaches.