title: Biochemical and Genetic Bases of Indole-3-Acetic Acid (Auxin Phytohormone) Degradation by the Plant-Growth-Promoting Rhizobacterium Paraburkholderia phytofirmans PsJN.
abstract: Several bacteria use the plant hormone indole-3-acetic acid (IAA) as a sole carbon and energy source. A cluster of genes (named iac) encoding IAA degradation has been reported in Pseudomonas putida 1290, but the functions of these genes are not completely understood. The plant-growth-promoting rhizobacterium Paraburkholderia phytofirmans PsJN harbors iac gene homologues in its genome, but with a different gene organization and context than those of P. putida 1290. The iac gene functions enable P. phytofirmans to use IAA as a sole carbon and energy source. Employing a heterologous expression system approach, P. phytofirmans iac genes with previously undescribed functions were associated with specific biochemical steps. In addition, two uncharacterized genes, previously unreported in P. putida and found to be related to major facilitator and tautomerase superfamilies, are involved in removal of an IAA metabolite called dioxindole-3-acetate. Similar to the case in strain 1290, IAA degradation proceeds through catechol as intermediate, which is subsequently degraded by ortho-ring cleavage. A putative two-component regulatory system and a LysR-type regulator, which apparently respond to IAA and dioxindole-3-acetate, respectively, are involved in iac gene regulation in P. phytofirmans These results provide new insights about unknown gene functions and complex regulatory mechanisms in IAA bacterial catabolism.
  
  
  
  This study describes indole-3-acetic acid (auxin phytohormone) degradation in the well-known betaproteobacterium P. phytofirmans PsJN and comprises a complete description of genes, some of them with previously unreported functions, and the general basis of their gene regulation. This work contributes to the understanding of how beneficial bacteria interact with plants, helping them to grow and/or to resist environmental stresses, through a complex set of molecular signals, in this case through degradation of a highly relevant plant hormone.
authors: Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Santiago, Chile.|Millennium Nucleus Center for Plant Systems and Synthetic Biology, Santiago, Chile.|Center of Applied Ecology and Sustainability, Santiago, Chile.
authors: Raúl
authors: R
authors: Donoso
authors: Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Santiago, Chile.|Millennium Nucleus Center for Plant Systems and Synthetic Biology, Santiago, Chile.|Center of Applied Ecology and Sustainability, Santiago, Chile.
authors: Pablo
authors: P
authors: Leiva-Novoa
authors: Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Santiago, Chile.|Millennium Nucleus Center for Plant Systems and Synthetic Biology, Santiago, Chile.|Center of Applied Ecology and Sustainability, Santiago, Chile.
authors: Ana
authors: A
authors: Zúñiga
authors: Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Santiago, Chile.|Millennium Nucleus Center for Plant Systems and Synthetic Biology, Santiago, Chile.|Center of Applied Ecology and Sustainability, Santiago, Chile.
authors: Tania
authors: T
authors: Timmermann
authors: Departamento de Farmacia, Facultad de Química, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors: Gonzalo
authors: G
authors: Recabarren-Gajardo
authors: Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Santiago, Chile bernardo.gonzalez@uai.cl.|Millennium Nucleus Center for Plant Systems and Synthetic Biology, Santiago, Chile.|Center of Applied Ecology and Sustainability, Santiago, Chile.
authors: Bernardo
authors: B
authors: González
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D042521:Burkholderiaceae / Q000235:genetics* / Q000378:metabolism* / Q000502:physiology; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D007210:Indoleacetic Acids / Q000378:metabolism*; D063245:Plant Development; D010937:Plant Growth Regulators / Q000737:chemistry / Q000378:metabolism*; D016958:Pseudomonas putida / Q000235:genetics / Q000378:metabolism; D013312:Stress, Physiological / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; C030737:indoleacetic acid
keywords: Paraburkholderia phytofirmans; iac genes; indole-3-acetic acid catabolism; plant-growth-promoting rhizobacteria