Timely expression of the Arabidopsis stoma-fate master regulator MUTE is required for specification of other epidermal cell types

Plant J. 2013 Sep;75(5):808-22. doi: 10.1111/tpj.12244. Epub 2013 Jun 21.


Epidermal differentiation in Arabidopsis thaliana aerial organs involves stomatal lineage development. Lineages derive from meristemoids, which arise from asymmetric divisions of protodermal cells. Each meristemoid divides repeatedly in an inward spiral before it transits to a guard mother cell (GMC) that produces the stoma, leaving a trail of surrounding stomatal lineage ground cells (SLGCs) that eventually differentiate into endoreplicated pavement cells. MUTE is a bHLH transcription factor that is expressed in late meristemoids and drives their transition to GMCs. Loss-of-function mute mutants are stomata-less dwarf plants with arrested lineages, in which stunted putative SLGCs surround a halted meristemoid. We analysed MUTE functions using a chemically inducible system for mute-3 complementation based on conditional MUTE expression in its normal domain. Continuous induction from germination produced stomata-bearing, normal-sized plants with viable mute-3 seeds. In 2-week-old mute-3 cotyledons, meristemoids appeared to retain their identity and synchronously formed stomata in response to induced MUTE expression. However, arrested SLGCs were not complemented: many produced stomata, leading to stomatal clusters, and others remained unexpanded and diploid. In contrast, non-lineage pavement cells, which are under-endoreplicated in mute-3, expanded and increased their ploidy level upon induction, showing that the lack of response of SLGCs is specific to this arrested cell type. Leaf phenotypic mosaics include wild-type lineages and adjacent mute-3 lineages, whose meristemoids and putative SLGCs remained arrested, indicating that the role of MUTE in SLGC fate is strictly lineage-autonomous. These results show that timely MUTE expression is essential to prevent stomatal fate in SLGCs and to promote their differentiation as pavement cells.

Keywords: Arabidopsis thaliana; MUTE; cell fate; epidermis development; meristemoid; stomata lineage ground cell.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / cytology
  • Arabidopsis / genetics
  • Arabidopsis / growth & development*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism
  • Arabidopsis Proteins / physiology*
  • Basic Helix-Loop-Helix Transcription Factors / genetics
  • Basic Helix-Loop-Helix Transcription Factors / metabolism
  • Basic Helix-Loop-Helix Transcription Factors / physiology*
  • Cell Differentiation / genetics*
  • Estradiol / pharmacology
  • Gene Expression Profiling
  • Gene Expression Regulation, Plant
  • Genetic Markers
  • Phenotype
  • Plant Stomata / genetics
  • Plant Stomata / growth & development*
  • Plant Stomata / ultrastructure
  • Ploidies


  • Arabidopsis Proteins
  • Basic Helix-Loop-Helix Transcription Factors
  • Genetic Markers
  • MUTE protein, Arabidopsis
  • Estradiol