title: Origin and function of stomata in the moss Physcomitrella patens.
abstract: Stomata are microscopic valves on plant surfaces that originated over 400 million years (Myr) ago and facilitated the greening of Earth's continents by permitting efficient shoot-atmosphere gas exchange and plant hydration1. However, the core genetic machinery regulating stomatal development in non-vascular land plants is poorly understood2-4and their function has remained a matter of debate for a century5. Here, we show that genes encoding the two basic helix-loop-helix proteins PpSMF1 (SPEECH, MUTE and FAMA-like) and PpSCREAM1 (SCRM1) in the moss Physcomitrella patens are orthologous to transcriptional regulators of stomatal development in the flowering plant Arabidopsis thaliana and essential for stomata formation in moss. Targeted P. patens knockout mutants lacking either PpSMF1 or PpSCRM1 develop gametophytes indistinguishable from wild-type plants but mutant sporophytes lack stomata. Protein-protein interaction assays reveal heterodimerization between PpSMF1 and PpSCRM1, which, together with moss-angiosperm gene complementations6, suggests deep functional conservation of the heterodimeric SMF1 and SCRM1 unit is required to activate transcription for moss stomatal development, as in A. thaliana7. Moreover, stomata-less sporophytes of ΔPpSMF1 and ΔPpSCRM1 mutants exhibited delayed dehiscence, implying stomata might have promoted dehiscence in the first complex land-plant sporophytes.
authors.affiliation: Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de Mexico, Cuernavaca 62210, Mexico.
authors.forename: Caspar C
authors.initials: CC
authors.lastname: Chater
authors.affiliation: Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Caine
authors.affiliation: Plant Biotechnology, Faculty of Biology, University of Freiburg, Schaenzlestraße 1, 79104 Freiburg, Germany.
authors.forename: Marta
authors.initials: M
authors.lastname: Tomek
authors.affiliation: Royal College of Veterinary Surgeons, Belgravia House, 62-64 Horseferry Road, London SW1P 2AF, UK.
authors.forename: Simon
authors.initials: S
authors.lastname: Wallace
authors.affiliation: Centre for Plant Sciences, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Kamisugi
authors.affiliation: Centre for Plant Sciences, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Cuming
authors.affiliation: Plant Biotechnology, Faculty of Biology, University of Freiburg, Schaenzlestraße 1, 79104 Freiburg, Germany.
authors.forename: Daniel
authors.identifier: 0000-0002-2166-0716
authors.initials: D
authors.lastname: Lang
authors.affiliation: Department of Molecular Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48109-1048, USA.
authors.forename: Cora A
authors.initials: CA
authors.lastname: MacAlister
authors.affiliation: Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK.
authors.forename: Stuart
authors.initials: S
authors.lastname: Casson
authors.affiliation: HHMI and Department of Biology, Stanford University, Stanford, California 94305-5020, USA.
authors.forename: Dominique C
authors.initials: DC
authors.lastname: Bergmann
authors.affiliation: Plant Biotechnology, Faculty of Biology, University of Freiburg, Schaenzlestraße 1, 79104 Freiburg, Germany.
authors.forename: Eva L
authors.initials: EL
authors.lastname: Decker
authors.affiliation: Plant Molecular Cell Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, LMU Biocenter, Großhaderner Straße 2, 82152 Planegg-Martinsried, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Frank
authors.affiliation: Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK.
authors.forename: Julie E
authors.initials: JE
authors.lastname: Gray
authors.affiliation: Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK.
authors.forename: Andrew
authors.identifier: 0000-0002-9703-0745
authors.initials: A
authors.lastname: Fleming
authors.affiliation: Plant Biotechnology, Faculty of Biology, University of Freiburg, Schaenzlestraße 1, 79104 Freiburg, Germany.|BIOSS - Centre for Biological Signalling Studies, 79104 Freiburg, Germany.
authors.forename: Ralf
authors.identifier: 0000-0002-5496-6711
authors.initials: R
authors.lastname: Reski
authors.affiliation: Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK.
authors.forename: David J
authors.initials: DJ
authors.lastname: Beerling
mesh_terms: D019068:Bryopsida / Q000235:genetics* / Q000254:growth & development*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000502:physiology*; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D054046:Plant Stomata / Q000235:genetics / Q000254:growth & development*
chemical_list: D010940:Plant Proteins