Monday, December 4, 2017
Brassinosteroids effect during adventitious rooting in Arabidopsis involves a complex interplay with auxin
Centre de Ressources Régionales en Biologie Moléculaire, Université de Picardie Jules Verne (UPJV), EA3900 Biologie des Plantes et Innovations (BIOPI), Amiens, France
Adventitious rooting is a complex genetic trait controlled by multiple environmental and endogenous factors, among which auxin plays a central role. In the past few years, it was shown that the balance between the AUXIN RESPONSE FACTORs ARF6, ARF8 and ARF17 was crucial for fine-tuning adventitious root (AR) initiation in the Arabidopsis hypocotyl [1, 2]. More recently, the phosphorylation of two ARF proteins by the GSK3-like kinase BRASSINOSTEROID INSENSITIVE2 (BIN2) was shown to potentiate auxin signaling output during lateral root organogenesis in Arabidopsis . In addition, ARF6, the phytochrome interacting factor4 (PIF4) and the brassinosteroid-signaling transcription factor BRASSINAZOLE-RESISTANT1 (BZR1) were recently shown to cooperatively regulate large numbers of common target genes in Arabidopsis hypocotyl . These results highlighted the function of brassinosteroid (BR) signaling as modulator of auxin signaling efficiency during hypocotyl and root development. This led us to investigate the role of BR signaling in the control of adventitious root initiation in Arabidopsis hypocotyl. By using reverse genetics and pharmacological approaches, we analyzed the impact disruption or enhancement at each level of BR signaling pathway could have on adventitious rooting. We showed that BR is a positive regulator of AR initiation through activation of the receptor BRI1 but also that BIN2/BIL1/BIL2 GSK3-like kinase proteins are required, although they are known as antagonistic of BRI1 in the BR signaling pathway. In order to understand the role of BR signaling in this process, we performed a RNA deep-sequencing experiment in hypocotyls treated with the hormone. BR induced a rapid, transitory and strong effect on the transcriptome with major changes in gene expression related to several hormone pathways especially auxin. Taken together these results suggest that AR initiation is controlled by a complex regulatory network involving early hormonal regulations in which BR seems to play a major role. In addition, our study on GSK3-like shows that they are likely to act independently, interacting with BR and auxin signaling to trigger the initiation of AR primordia.
François Jobert1,3 , Jan Drouaud1 , Hervé Demailly1 , Stéphanie Guénin1 , Luciane Zabijak2 , Paulo Marcelo2 , Yvon Jaillais4 , Jérôme Pelloux3 and Laurent Gutierrez1
1 Centre de Ressources Régionales en Biologie Moléculaire, Université de Picardie Jules Verne (UPJV), Amiens, France ;
2 Plateforme d’Imagerie Cellulaire et d’Analyse Protéomique, UPJV, Amiens, France ;
3 EA3900 Biologie des Plantes et Innovations (BIOPI), UPJV, Amiens, France ;
4 Laboratoire Reproduction et Développement des Plantes (RDP), CNRS, ENS, Lyon, France.
 Gutierrez, L. et al. (2009). The Plant Cell 21, 3119–3132.
 Gutierrez, L. et al. (2012). The Plant Cell 24, 2515–2527.
 Cho, H. et al. (2013). Nature Cell Biology 16, 66–76.
 Oh, E. et al. (2014). eLife 3, e03031.
Contact : Arthur Poitout