title: Timely expression of the Arabidopsis stoma-fate master regulator MUTE is required for specification of other epidermal cell types.
abstract: 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.
authors.affiliation: Facultad de Ciencias Ambientales y Bioquímica, Universidad de Castilla la Mancha, Avenida Carlos III s/n, Toledo, 45071, Spain.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Triviño
authors.forename: Mar
authors.initials: M
authors.lastname: Martín-Trillo
authors.forename: Isabel
authors.initials: I
authors.lastname: Ballesteros
authors.forename: Dolores
authors.initials: D
authors.lastname: Delgado
authors.forename: Alberto
authors.initials: A
authors.lastname: de Marcos
authors.forename: Bénédicte
authors.initials: B
authors.lastname: Desvoyes
authors.forename: Crisanto
authors.initials: C
authors.lastname: Gutiérrez
authors.forename: Montaña
authors.initials: M
authors.lastname: Mena
authors.forename: Carmen
authors.initials: C
authors.lastname: Fenoll
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002454:Cell Differentiation / Q000235:genetics*; D004958:Estradiol / Q000494:pharmacology; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D005819:Genetic Markers; D010641:Phenotype; D054046:Plant Stomata / Q000235:genetics / Q000254:growth & development* / Q000648:ultrastructure; D011003:Ploidies
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D004958:Estradiol; D005819:Genetic Markers; C517479:MUTE protein, Arabidopsis
keywords: Arabidopsis thaliana; MUTE; cell fate; epidermis development; meristemoid; stomata lineage ground cell