title: Root gravitropism and root hair development constitute coupled developmental responses regulated by auxin homeostasis in the Arabidopsis root apex.
abstract: Active polar transport establishes directional auxin flow and the generation of local auxin gradients implicated in plant responses and development. Auxin modulates gravitropism at the root tip and root hair morphogenesis at the differentiation zone. Genetic and biochemical analyses provide evidence for defective basipetal auxin transport in trh1 roots. The trh1, pin2, axr2 and aux1 mutants, and transgenic plants overexpressing PIN1, all showing impaired gravity response and root hair development, revealed ectopic PIN1 localization. The auxin antagonist hypaphorine blocked root hair elongation and caused moderate agravitropic root growth, also leading to PIN1 mislocalization. These results suggest that auxin imbalance leads to proximal and distal developmental defects in Arabidopsis root apex, associated with agravitropic root growth and root hair phenotype, respectively, providing evidence that these two auxin-regulated processes are coupled. Cell-specific subcellular localization of TRH1-YFP in stele and epidermis supports TRH1 engagement in auxin transport, and hence impaired function in trh1 causes dual defects of auxin imbalance. The interplay between intrinsic cues determining root epidermal cell fate through the TTG/GL2 pathway and environmental cues including abiotic stresses modulates root hair morphogenesis. As a consequence of auxin imbalance in Arabidopsis root apex, ectopic PIN1 mislocalization could be a risk aversion mechanism to trigger root developmental responses ensuring root growth plasticity.
authors.affiliation: Department of Agricultural Biotechnology, Agricultural University of Athens, Iera Odos 75, Athens, 118 55, Greece.
authors.forename: Stamatis
authors.initials: S
authors.lastname: Rigas
authors.affiliation: Institute of Biology II, Faculty of Biology, Albert-Ludwigs-University of Freiburg, Schänzlestrasse 1, D-79104, Freiburg, Germany.
authors.forename: Franck Anicet
authors.initials: FA
authors.lastname: Ditengou
authors.affiliation: Department of Forest Genetics and Plant Physiology, Umeå Plant Science Centre, Swedish University of Agricultural Sciences, SE-901 83, Umeå, Sweden.
authors.forename: Karin
authors.initials: K
authors.lastname: Ljung
authors.affiliation: Department of Agricultural Biotechnology, Agricultural University of Athens, Iera Odos 75, Athens, 118 55, Greece.
authors.forename: Gerasimos
authors.initials: G
authors.lastname: Daras
authors.affiliation: Institute of Biology II, Faculty of Biology, Albert-Ludwigs-University of Freiburg, Schänzlestrasse 1, D-79104, Freiburg, Germany.
authors.forename: Olaf
authors.initials: O
authors.lastname: Tietz
authors.affiliation: Institute of Biology II, Faculty of Biology, Albert-Ludwigs-University of Freiburg, Schänzlestrasse 1, D-79104, Freiburg, Germany.|Centre of Biological Systems Analysis, Albert-Ludwigs-University of Freiburg, Habsburgerstr. 49, D-79104, Freiburg, Germany.|Freiburg Institute of Advanced Sciences (FRIAS), Albert-Ludwigs-University of Freiburg, Albertstrasse 19, D-79104, Freiburg, Germany.|Centre for Biological Signalling Studies (bioss), Albert-Ludwigs-University of Freiburg, Albertstrasse 19, D-79104, Freiburg, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Palme
authors.affiliation: Department of Agricultural Biotechnology, Agricultural University of Athens, Iera Odos 75, Athens, 118 55, Greece.
authors.forename: Polydefkis
authors.initials: P
authors.lastname: Hatzopoulos
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001692:Biological Transport; D027682:Cation Transport Proteins / Q000378:metabolism / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D018522:Gravitropism; D006706:Homeostasis; D007210:Indoleacetic Acids / Q000378:metabolism*; D007211:Indoles / Q000737:chemistry / Q000494:pharmacology; D026901:Membrane Transport Proteins / Q000032:analysis / Q000378:metabolism; D018519:Meristem / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D010937:Plant Growth Regulators / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000254:growth & development / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D027682:Cation Transport Proteins; D007210:Indoleacetic Acids; D007211:Indoles; D026901:Membrane Transport Proteins; C116363:PIN1 protein, Arabidopsis; D010937:Plant Growth Regulators; C474309:TRH1 protein, Arabidopsis; C001529:lenticin