Transcription factor control of asymmetric cell divisions that establish the stomatal lineage

Nature. 2007 Feb 1;445(7127):537-40. doi: 10.1038/nature05491. Epub 2006 Dec 20.


The establishment of new cell lineages during development often requires a symmetry-breaking event. An asymmetric division in the epidermis of plants initiates a lineage that ultimately produces stomatal guard cells. Stomata are pores in the epidermis that serve as the main conduits for gas exchange between plants and the atmosphere; they are critical for photosynthesis and exert a major influence on global carbon and water cycles. Recent studies implicated intercellular signalling in preventing the inappropriate production of stomatal complexes. Genes required to make stomata, however, remained elusive. Here we report the identification of a gene, SPEECHLESS (SPCH), encoding a basic helix-loop-helix (bHLH) transcription factor that is necessary and sufficient for the asymmetric divisions that establish the stomatal lineage in Arabidopsis thaliana. We demonstrate that SPCH and two paralogues are successively required for the initiation, proliferation and terminal differentiation of cells in the stomatal lineage. The stomatal bHLHs define a molecular pathway sufficient to create one of the key cell types in plants. Similar molecules and regulatory mechanisms are used during muscle and neural development, highlighting a conserved use of closely related bHLHs for cell fate specification and differentiation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Arabidopsis / cytology*
  • Arabidopsis / genetics
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism
  • Basic Helix-Loop-Helix Transcription Factors / genetics
  • Basic Helix-Loop-Helix Transcription Factors / metabolism*
  • Cell Differentiation*
  • Cell Division
  • Cell Lineage*
  • Cell Polarity*
  • Cloning, Molecular
  • Gene Expression Regulation, Plant
  • Molecular Sequence Data
  • Plant Epidermis / cytology*
  • Plant Epidermis / metabolism


  • Arabidopsis Proteins
  • Basic Helix-Loop-Helix Transcription Factors
  • FAMA protein, Arabidopsis
  • MUTE protein, Arabidopsis
  • SPEECHLESS protein, Arabidopsis

Associated data

  • GENBANK/DQ863645
  • GENBANK/DQ864972
  • GENBANK/DQ868373