title: Robust root growth in altered hydrotropic response1 (ahr1) mutant of Arabidopsis is maintained by high rate of cell production at low water potential gradient.
abstract: Hydrotropism is the directional root growth response determined by water stimulus. In a water potential gradient system (WPGS) the roots of the Arabidopsis wild type have a diminished root growth compared to normal medium (NM). In contrast, the altered hydrotropic response1 (ahr1) mutant roots maintain their robust growth in the same WPGS. The aims of this work were to ascertain how ahr1 roots could sustain growth in the WPGS, with a special focus on the integration of cellular processes involved in the signaling that determines root growth during abiotic stress and their relation to hydrotropism. Cellular analysis of the root apical meristem of ahr1 mutant contrary to the wild type showed an absence of changes in the meristem length, the elongation zone length, the length of fully elongated cells, and the cell cycle duration. The robust and steady root growth of ahr1 seedlings in the WPGS is explained by the mutant capacity to maintain cell production and cell elongation at the same level as in the NM. Analysis of auxin response at a transcriptional level showed that roots of the ahr1 mutant had a lower auxin response when grown in the WPGS, compared to wild type, indicating that auxin signaling participates in attenuation of root growth under water stress conditions. Also, wild type plants exhibited a high increase in proline content while ahr1 mutants showed minimum changes in the Normal Medium→Water Stress Medium (NM→WSM), a lower water potential gradient system than the WPGS. Accordingly, in this condition, gene expression of Δ1-6 Pyrroline-5-Carboxylate Synthetase1 (P5CS1) involved in proline synthesis strongly increased in wild type but not in ahr1 seedlings. The ahr1 phenotype shows unique features since the mutant root cells continue to proliferate and grow in the presence of a progressively negative water potential gradient at a level comparable to wild type growing in the NM. As such, it represents an exceptional resource for understanding hydrotropism.
authors.affiliation: Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Cuernavaca, Mor. 62250, México.
authors.forename: Amed
authors.initials: A
authors.lastname: Salazar-Blas
authors.affiliation: Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Cuernavaca, Mor. 62250, México.
authors.forename: Laura
authors.initials: L
authors.lastname: Noriega-Calixto
authors.affiliation: Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Cuernavaca, Mor. 62250, México.
authors.forename: María E
authors.initials: ME
authors.lastname: Campos
authors.affiliation: Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Cuernavaca, Mor. 62250, México.
authors.forename: Delfeena
authors.initials: D
authors.lastname: Eapen
authors.affiliation: Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Cuernavaca, Mor. 62250, México.
authors.forename: Tania
authors.initials: T
authors.lastname: Cruz-Vázquez
authors.affiliation: Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Cuernavaca, Mor. 62250, México.
authors.forename: Luis
authors.initials: L
authors.lastname: Castillo-Olamendi
authors.affiliation: Doctorado en Ciencias Biológicas, Facultad de Ciencias UNAM, Centro de Desarrollo de Productos Bióticos-IPN, Calle CeProBi No. 8, Col. San Isidro, Yautepec Morelos 62731, México.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Sepulveda-Jiménez
authors.affiliation: Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Cuernavaca, Mor. 62250, México.
authors.forename: Helena
authors.initials: H
authors.lastname: Porta
authors.affiliation: Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Cuernavaca, Mor. 62250, México.
authors.forename: Joseph G
authors.initials: JG
authors.lastname: Dubrovsky
authors.affiliation: Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Cuernavaca, Mor. 62250, México. Electronic address: gladys@ibt.unam.mx.
authors.forename: Gladys I
authors.initials: GI
authors.lastname: Cassab
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002453:Cell Cycle; D003681:Dehydration; D017930:Genes, Reporter; D050698:Glutamate-5-Semialdehyde Dehydrogenase / Q000235:genetics / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism; D010937:Plant Growth Regulators / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D011392:Proline / Q000378:metabolism; D036226:Seedlings / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D015398:Signal Transduction; D018523:Tropism; D014867:Water / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D009097:Multienzyme Complexes; D010937:Plant Growth Regulators; C583835:delta(1)-pyrroline-5-carboxylate synthetase, Arabidopsis; D014867:Water; D011392:Proline; D050698:Glutamate-5-Semialdehyde Dehydrogenase; D017853:Phosphotransferases (Alcohol Group Acceptor)
keywords: Auxin; Cell cycle; Proline; Root hydrotropism; Water potential gradient