title: An auxin-mediated shift toward growth isotropy promotes organ formation at the shoot meristem in Arabidopsis.
abstract: To control morphogenesis, molecular regulatory networks have to interfere with the mechanical properties of the individual cells of developing organs and tissues, but how this is achieved is not well known. We study this issue here in the shoot meristem of higher plants, a group of undifferentiated cells where complex changes in growth rates and directions lead to the continuous formation of new organs. Here, we show that the plant hormone auxin plays an important role in this process via a dual, local effect on the extracellular matrix, the cell wall, which determines cell shape. Our study reveals that auxin not only causes a limited reduction in wall stiffness but also directly interferes with wall anisotropy via the regulation of cortical microtubule dynamics. We further show that to induce growth isotropy and organ outgrowth, auxin somehow interferes with the cortical microtubule-ordering activity of a network of proteins, including AUXIN BINDING PROTEIN 1 and KATANIN 1. Numerical simulations further indicate that the induced isotropy is sufficient to amplify the effects of the relatively minor changes in wall stiffness to promote organogenesis and the establishment of new growth axes in a robust manner.
authors.affiliation: Laboratoire de Reproduction et Développement des Plantes, INRA, CNRS, ENS, UCB Lyon 1, 46 Allée d'Italie, 69364 Lyon Cedex 07, France. Electronic address: massimiliano.sassi@ens-lyon.fr.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Sassi
authors.affiliation: Laboratoire de Reproduction et Développement des Plantes, INRA, CNRS, ENS, UCB Lyon 1, 46 Allée d'Italie, 69364 Lyon Cedex 07, France; CIRAD, INRIA, INRA, Virtual Plants INRIA Team, UMR AGAP, Avenue Agropolis, TA 108/02, 34398 Montpellier Cedex 5, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Ali
authors.affiliation: CIRAD, INRIA, INRA, Virtual Plants INRIA Team, UMR AGAP, Avenue Agropolis, TA 108/02, 34398 Montpellier Cedex 5, France.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Boudon
authors.affiliation: Laboratoire de Reproduction et Développement des Plantes, INRA, CNRS, ENS, UCB Lyon 1, 46 Allée d'Italie, 69364 Lyon Cedex 07, France.
authors.forename: Gladys
authors.initials: G
authors.lastname: Cloarec
authors.affiliation: Laboratoire de Reproduction et Développement des Plantes, INRA, CNRS, ENS, UCB Lyon 1, 46 Allée d'Italie, 69364 Lyon Cedex 07, France.
authors.forename: Ursula
authors.initials: U
authors.lastname: Abad
authors.affiliation: Laboratoire de Reproduction et Développement des Plantes, INRA, CNRS, ENS, UCB Lyon 1, 46 Allée d'Italie, 69364 Lyon Cedex 07, France.
authors.forename: Coralie
authors.initials: C
authors.lastname: Cellier
authors.affiliation: Department of Plant Systems Biology, Flanders Institute for Biotechnology (VIB), and Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, 9052 Gent, Belgium; Institute of Science and Technology Austria (IST Austria), Am Campus 1, 3400 Klosterneuburg, Austria.
authors.forename: Xu
authors.initials: X
authors.lastname: Chen
authors.affiliation: Laboratoire d'Informatique, de Robotique et de Microléctronique de Montpellier, CNRS, Université Montpellier 2, 34090 Montpellier, France.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Gilles
authors.affiliation: Laboratoire de Reproduction et Développement des Plantes, INRA, CNRS, ENS, UCB Lyon 1, 46 Allée d'Italie, 69364 Lyon Cedex 07, France; Laboratoire Joliot Curie, CNRS, ENS Lyon, Université de Lyon, 46 Allée d'Italie, 69364 Lyon Cedex 07, France.
authors.forename: Pascale
authors.initials: P
authors.lastname: Milani
authors.affiliation: Department of Plant Systems Biology, Flanders Institute for Biotechnology (VIB), and Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, 9052 Gent, Belgium; Institute of Science and Technology Austria (IST Austria), Am Campus 1, 3400 Klosterneuburg, Austria.
authors.forename: Jiří
authors.initials: J
authors.lastname: Friml
authors.affiliation: Laboratoire de Reproduction et Développement des Plantes, INRA, CNRS, ENS, UCB Lyon 1, 46 Allée d'Italie, 69364 Lyon Cedex 07, France.
authors.forename: Teva
authors.initials: T
authors.lastname: Vernoux
authors.affiliation: CIRAD, INRIA, INRA, Virtual Plants INRIA Team, UMR AGAP, Avenue Agropolis, TA 108/02, 34398 Montpellier Cedex 5, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Godin
authors.affiliation: Laboratoire de Reproduction et Développement des Plantes, INRA, CNRS, ENS, UCB Lyon 1, 46 Allée d'Italie, 69364 Lyon Cedex 07, France; Laboratoire Joliot Curie, CNRS, ENS Lyon, Université de Lyon, 46 Allée d'Italie, 69364 Lyon Cedex 07, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Hamant
authors.affiliation: Laboratoire de Reproduction et Développement des Plantes, INRA, CNRS, ENS, UCB Lyon 1, 46 Allée d'Italie, 69364 Lyon Cedex 07, France. Electronic address: jan.traas@ens-lyon.fr.
authors.forename: Jan
authors.initials: J
authors.lastname: Traas
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D017360:Arabidopsis / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000378:metabolism; D001696:Biomechanical Phenomena; D002473:Cell Wall / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism*; D000074201:Katanin; D018519:Meristem / Q000254:growth & development; D010937:Plant Growth Regulators / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism; D018520:Plant Shoots / Q000254:growth & development; D011956:Receptors, Cell Surface / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D010940:Plant Proteins; D011956:Receptors, Cell Surface; C083846:auxin-binding protein 1; D000251:Adenosine Triphosphatases; C436244:KTN1 protein, Arabidopsis; D000074201:Katanin