Spatial analysis of brassinosteroid signaling in the stem cell niche of Arabidopsis primary root = Caracterització molecular de la funció de BRI1 en les cèl•lules mare de l?arrel d?Arabidopsis

• Autores: Josep Vilarrasa Blasi
• Directores de la Tesis: Marc Valls (dir. tes.), Ana I Caño Delgado (dir. tes.)
• Lectura: En la Universitat de Barcelona ( España ) en 2014
• Idioma: inglés
• Tribunal Calificador de la Tesis: Pedro Luís Rodríguez Egea (presid.), Teresa Altabella Artigas (secret.), Sacco de Vries (voc.)
• Materias:
  • Ciencias de la vida
    • Biología vegetal (botánica)
      • Genética vegetal
      • Desarrollo vegetal
      • Fisiología vegetal
• Enlaces
  • Tesis en acceso abierto en:  TDX  Dipòsit Digital de la UB 
• Resumen

  • The present PhD thesis work reports the molecular and genetic dissection for the role of plant steroid hormones Brassinosteroids (BRs) in root growth and development of Arabidopsis thaliana (Arabidopsis). A genetic, physiological and cellular analysis of existing BR mutants, together with the discovery of a novel pathway for the control of BR mediated stem cell divisions. The results presented here provide experimental evidence for a role of BRs in stem cell homeostasis in the primary root of Arabidopsis. Specifically, BRs promote columella stem cell differentiation and the division of a set of low mitotic cells called quiescent center (QC) that maintain the surrounding stem cells. Using a microgenomic approach, a novel BR signaling component, BRAVO (Brassinosteroids at Vascular and Organizing Centre) has been identified that is specifically expressed in the stem cells. BRAVO encodes a R2-R3 MYB transcription factor (MYB56) that acts as a negative regulator of BR-mediated QC divisions. This study uncovers a fine example of negative regulation model; BRAVO is directly repressed and interacts with BES1 creating a molecular switch that controls QC divisions. The work carried out during this PhD thesis shed light to a new function of brassinosteroids in the regulation of stem cells. BRAVO provides plasticity to the stem cells to response to DNA damage, and at the same time robustness to ensure QC function upon damage. The control of plant stem cell homeostasis is pivotal to understand plant adaptation to environmental changing conditions and provides a new mechanism to understand plants life span.