title: The Arabidopsis thaliana Mob1A gene is required for organ growth and correct tissue patterning of the root tip.
abstract: OBJECTIVE
  The Mob1 family includes a group of kinase regulators conserved throughout eukaryotes. In multicellular organisms, Mob1 is involved in cell proliferation and apoptosis, thus controlling appropriate cell number and organ size. These functions are also of great importance for plants, which employ co-ordinated growth processes to explore the surrounding environment and respond to changing external conditions. Therefore, this study set out to investigate the role of two Arabidopsis thaliana Mob1-like genes, namely Mob1A and Mob1B, in plant development.
  
  
  METHODS
  A detailed spatio-temporal analysis of Mob1A and Mob1B gene expression was performed by means of bioinformatic tools, the generation of expression reporter lines and in situ hybridization of gene-specific probes. To explore the function of the two genes in plant development, knock-out and knock-down mutants were isolated and their phenotype quantitatively characterized.
  
  
  RESULTS
  Transcripts of the two genes were detected in specific sets of cells in all plant organs. Mob1A was upregulated by several stress conditions as well as by abscisic acid and salicylic acid. A knock-out mutation in Mob1B did not cause any visible defect in plant development, whereas suppression of Mob1A expression affected organ growth and reproduction. In the primary root, reduced levels of Mob1A expression brought about severe defects in tissue patterning of the stem cell niche and columella and led to a decrease in meristem size. Moreover, loss of Mob1A function resulted in a higher sensitivity of root growth to abscisic acid.
  
  
  CONCLUSIONS
  Taken together, the results indicate that arabidopsis Mob1A is involved in the co-ordination of tissue patterning and organ growth, similarly to its orthologues in other multicellular eukaryotes. In addition, Mob1A serves a plant-specific function by contributing to growth adjustments in response to stress conditions.
authors.affiliation: Institute of Biology II/Molecular Plant Physiology, Faculty of Biology, Albert-Ludwigs-University of Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany.
authors.forename: Francesco
authors.initials: F
authors.lastname: Pinosa
authors.forename: Maura
authors.initials: M
authors.lastname: Begheldo
authors.forename: Taras
authors.initials: T
authors.lastname: Pasternak
authors.forename: Monica
authors.initials: M
authors.lastname: Zermiani
authors.forename: Ivan A
authors.initials: IA
authors.lastname: Paponov
authors.forename: Alexander
authors.initials: A
authors.lastname: Dovzhenko
authors.forename: Gianni
authors.initials: G
authors.lastname: Barcaccia
authors.forename: Benedetto
authors.initials: B
authors.lastname: Ruperti
authors.forename: Klaus
authors.initials: K
authors.lastname: Palme
mesh_terms: D000040:Abscisic Acid / Q000502:physiology; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D019521:Body Patterning; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D063245:Plant Development; D018517:Plant Roots / Q000254:growth & development*; D034622:RNA Interference
chemical_list: D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; C000589223:Mob1A protein, Arabidopsis thaliana; D000040:Abscisic Acid
keywords: Arabidopsis thaliana; Mob1; abscisic acid; columella; plant development; root tip; stem cell niche; tissue patterning