Browsing by Author "Donoso, Raul"

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    Aromatic compounds degradation plays a role in colonization of Arabidopsis thaliana and Acacia caven by Cupriavidus pinatubonensis JMP134
    (2012) Ledger, Thomas; Zuniga, Ana; Kraiser, Tatiana; Dasencich, Paola; Donoso, Raul; Perez-Pantoja, Danilo; Gonzalez, Bernardo
    Plant rhizosphere and internal tissues may constitute a relevant habitat for soil bacteria displaying high catabolic versatility towards xenobiotic aromatic compounds. Root exudates contain various molecules that are structurally related to aromatic xenobiotics and have been shown to stimulate bacterial degradation of aromatic pollutants in the rhizosphere. The ability to degrade specific aromatic components of root exudates could thus provide versatile catabolic bacteria with an advantage for rhizosphere colonization and growth. In this work, Cupriavidus pinatubonensis JMP134, a well-known aromatic compound degrader (including the herbicide 2,4-dichlorophenoxyacetate, 2,4-D), was shown to stably colonize Arabidopsis thaliana and Acacia caven plants both at the rhizoplane and endorhizosphere levels and to use root exudates as a sole carbon and energy source. No deleterious effects were detected on these colonized plants. When a toxic concentration of 2,4-D was applied to colonized A. caven, a marked resistance was induced in the plant, showing that strain JMP134 was both metabolically active and potentially beneficial to its host. The role for the beta-ketoadipate aromatic degradation pathway during plant root colonization by C. pinatubonensis JMP134 was investigated by gene inactivation. A C. pinatubonensis mutant derivative strain displayed a reduced ability to catabolise root exudates isolated from either plant host. In this mutant strain, a lower competence in the rhizosphere of A. caven was also shown, both in gnotobiotic in vitro cultures and in plant/soil microcosms.
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    Molecular and physiological analysis of indole-3-acetic acid degradation in Bradyrhizobium japonicum E109
    (2021) Torres, Daniela; Mongiardini, Elias; Donadio, Florencia; Donoso, Raul; Recabarren-Gajardo, Gonzalo; Gualpa, Jose; Spaepen, Stijn; Defez, Roberto; Lopez, Gaston; Bianco, Carmen; Cassan, Fabricio
    Bradyrhizobium japonicum E109 is a bacterium widely used for inoculants production in Argentina. It is known for its ability to produce several phytohormones and degrade indole-3-acetic acid (IAA). The genome sequence of B. japonicum E109 was recently analyzed and it showed the presence of genes related to the synthesis of IAA by indole-3-acetonitrile, indole-3-acetamide and tryptamine pathways. Nevertheless, B. japonicum E109 is not able to produce IAA and instead has the ability to degrade this hormone under saprophytic culture conditions. This work aimed to study the molecular and physio-logical features of IAA degradation and identify the genes responsible of this activity. In B. japonicum E109 we identified two sequences coding for a putative 3-phenylpropionate dioxygenase (subunits a and b) responsible for the IAA degradation that were homologous to the canonical cluster of iacC and iacD of Pseudomonas putida 1290. These genes form a separate cluster together with three additional genes with unknown functions. The degradation activity was found to be constitutively expressed in B. japonicum E109. As products of IAA degradation, we identified two compounds, 3-indoleacetic acid 2,3-oxide and 2-(2-hydroperoxy-3-hydroxyindolin-3-yl) acetic acid. Our report proposes, for the first time, a model for IAA degradation in Bradyrhizobium.