The BASL polarity protein controls a MAPK signaling feedback loop in asymmetric cell division

Dev Cell. 2015 Apr 20;33(2):136-49. doi: 10.1016/j.devcel.2015.02.022. Epub 2015 Apr 2.


Cell polarization is linked to fate determination during asymmetric division of plant stem cells, but the underlying molecular mechanisms remain unknown. In Arabidopsis, BREAKING OF ASYMMETRY IN THE STOMATAL LINEAGE (BASL) is polarized to control stomatal asymmetric division. A mitogen-activated protein kinase (MAPK) cascade determines terminal stomatal fate by promoting the degradation of the lineage determinant SPEECHLESS (SPCH). Here, we demonstrate that a positive-feedback loop between BASL and the MAPK pathway constitutes a polarity module at the cortex. Cortical localization of BASL requires phosphorylation mediated by MPK3/6. Phosphorylated BASL functions as a scaffold and recruits the MAPKKK YODA and MPK3/6 to spatially concentrate signaling at the cortex. Activated MPK3/6 reinforces the feedback loop by phosphorylating BASL and inhibits stomatal fate by phosphorylating SPCH. Polarization of the BASL-MAPK signaling feedback module represents a mechanism connecting cell polarity to fate differentiation during asymmetric stem cell division in plants.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Arabidopsis / growth & development*
  • Arabidopsis Proteins / metabolism*
  • Asymmetric Cell Division / genetics*
  • Basic Helix-Loop-Helix Transcription Factors / metabolism
  • Cell Cycle Proteins / metabolism*
  • Cell Differentiation
  • Cell Lineage / genetics
  • Cell Polarity / genetics
  • Gene Expression Regulation, Plant
  • MAP Kinase Kinase Kinases / metabolism
  • MAP Kinase Signaling System / genetics*
  • Mitogen-Activated Protein Kinase Kinases / metabolism
  • Mitogen-Activated Protein Kinases / metabolism
  • Phosphorylation
  • Plant Stomata / cytology
  • Plant Stomata / growth & development*
  • Tobacco / growth & development*


  • Arabidopsis Proteins
  • BASL protein, Arabidopsis
  • Basic Helix-Loop-Helix Transcription Factors
  • Cell Cycle Proteins
  • SPEECHLESS protein, Arabidopsis
  • AtMPK3 protein, Arabidopsis
  • MPK6 protein, Arabidopsis
  • Mitogen-Activated Protein Kinases
  • MAP Kinase Kinase Kinases
  • YODA protein, Arabidopsis
  • Mitogen-Activated Protein Kinase Kinases