A PHABULOSA/Cytokinin feedback loop controls root growth in Arabidopsis

R. Dello loio, C. Galinha, A.G. Fletcher, S.P. Grigg, A. Molnar, V. Willemsen, B. Scheres

Research output: Contribution to journalArticleAcademicpeer-review

70 Citations (Scopus)


The hormone cytokinin (CK) controls root length in Arabidopsis thaliana by defining where dividing cells, derived from stem cells of the root meristem, start to differentiate. However, the regulatory inputs directing CK to promote differentiation remain poorly understood. Here, we show that the HD-ZIPIII transcription factor PHABULOSA (PHB) directly activates the CK biosynthesis gene ISOPENTENYL TRANSFERASE 7 (IPT7), thus promoting cell differentiation and regulating root length. We further demonstrate that CK feeds back to repress both PHB and microRNA165, a negative regulator of PHB. These interactions comprise an incoherent regulatory loop in which CK represses both its activator and a repressor of its activator. We propose that this regulatory circuit determines the balance of cell division and differentiation during root development and may provide robustness against CK fluctuations.
Original languageEnglish
Pages (from-to)1699-1704
JournalCurrent Biology
Issue number18
Publication statusPublished - 2012


  • stem-cell niche
  • gene family
  • cytokinin
  • meristem
  • auxin
  • differentiation
  • expression
  • polarity
  • biosynthesis
  • nitrate

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