title: A novel role for STOMATAL CARPENTER 1 in stomata patterning.
abstract: Guard cells (GCs) are specialised cells within the plant epidermis which form stomatal pores, through which gas exchange can occur. The GCs derive through a specialised lineage of cell divisions which is specified by the transcription factor SPEECHLESS (SPCH), the expression of which can be detected in undifferentiated epidermal cells prior to asymmetric division. Other transcription factors may act before GC specification and be required for correct GC patterning. Previously, the DOF transcription factor STOMATAL CARPENTER 1 (SCAP1) was shown to be involved in GC function, by activating a set of GC-specific genes required for GC maturation and activity. It is thus far unknown whether SCAP1 can also affect stomatal development.
  
  
  
  Here we show that SCAP1 expression can also be observed in young leaf primordia, before any GC differentiation occurs. The study of transgenic plants carrying a proSCAP1:GUS-GFP transcriptional fusion, coupled with qPCR analyses, indicate that SCAP1 expression peaks in a temporal window which is coincident with expression of stomatal patterning genes. Independent scap1 loss-of-function mutants have a reduced number of GCs whilst SCAP1 over expression lines have an increased number of GCs, in addition to altered GC distribution and spacing patterns. The study of early markers for stomatal cell lineage in a background carrying gain-of-function alleles of SCAP1 revealed that, compared to the wild type, an increased number of protodermal cells are recruited in the GC lineage, which is reflected in an increased number of meristemoids.
  
  
  
  Our results suggest an early role for SCAP1 in GC differentiation. We propose that a function of SCAP1 is to integrate different aspects of GC biology including specification, spacing, maturation and function.
authors.affiliation: Dipartimento di Bioscienze, Università degli studi di Milano, Via Celoria 26, 20133, Milan, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Castorina
authors.affiliation: Department of Cell and Developmental Biology, John Innes Centre, Norwich, NR4 7UH, UK.
authors.forename: Samantha
authors.initials: S
authors.lastname: Fox
authors.affiliation: Dipartimento di Bioscienze, Università degli studi di Milano, Via Celoria 26, 20133, Milan, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Tonelli
authors.affiliation: Dipartimento di Bioscienze, Università degli studi di Milano, Via Celoria 26, 20133, Milan, Italy. massimo.galbiati@unimi.it.
authors.forename: Massimo
authors.initials: M
authors.lastname: Galbiati
authors.affiliation: Dipartimento di Bioscienze, Università degli studi di Milano, Via Celoria 26, 20133, Milan, Italy. lucio.conti@unimi.it.
authors.forename: Lucio
authors.identifier: 0000-0002-7837-4227
authors.initials: L
authors.lastname: Conti
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D019521:Body Patterning; D002454:Cell Differentiation; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D059828:Plant Cells / Q000378:metabolism*; D054046:Plant Stomata / Q000166:cytology / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; C000621907:SCAP1 protein, Arabidopsis
keywords: Arabidopsis; AtMYB60 (AT1G08810); DOF-type transcription factors; Guard Cells development; SCAP1 (AT5G65590); SPCH (AT5G53210)