title: OmGOGAT-disruption in the ericoid mycorrhizal fungus Oidiodendron maius induces reorganization of the N pathway and reduces tolerance to heavy-metals.
abstract: Mycorrhizal fungi are key mediators of soil-to-plant movement of mineral nutrients, including essential and non-essential metals. In soil conditions that facilitate mobilization of metal ions, potentially toxic metals can interfere with nitrogen metabolism in both plants and microorganisms. Less is known about possible relationships between nitrogen metabolism and responses to heavy metals. Aim of this study was to investigate this aspect in the ericoid mycorrhizal fungus Oidiodendron maius strain Zn, a metal tolerant ascomycete. Growth of O. maius Zn on zinc and cadmium containing media was significantly affected by the nitrogen source. Screening of a library of O. maius Zn random genetic transformants for sensitivity to heavy metals (zinc and cadmium) and oxidative stress (menadione) yielded a mutant strain that carried a partial deletion of the glutamate synthase (NADH-GOGAT EC 1.4.1.14) gene and its adjacent gene, the APC15 subunit of the anaphase promoting complex. Comparison of WT and OmGOGAT-OmAPC15 mutant strains indicated an impaired N-metabolism and altered stress tolerance, and assays on the OmAPC15-recomplemented strains ascribed the observed phenotypes to the deletion in the OmGOGAT gene. OmGOGAT disruption modified the nitrogen pathway, with a strong reduction of the associated glutamine synthetase (GS, EC 6.3.1.2) activity and an up-regulation of the alternative NADP-glutamate dehydrogenase (NADP-GDH, EC 1.4.1.4) pathway for glutamate biosynthesis. Unless they were supplemented with glutamine, O. maius Zn transformants lacking OmGOGAT were very sensitive to zinc. These results highlight the importance of nitrogen metabolism not only for nitrogen assimilation and transformation, but also for stress tolerance. For mycorrhizal fungi, such as O. maius, this may bear consequences not only to the fungus, but also to the host plant.
authors.affiliation: Department of Life Sciences and Systems Biology, University of Torino, Viale Mattioli 25, 10125 Torino, Italy; Université de Lorraine, UMR-1136 Interactions Arbres Microorganismes, Faculté des Sciences et Technologies, BP 70239, F-54506 Vandoeuvre-lès-Nancy, France. Electronic address: radhouane.khouja@gmail.com.
authors.forename: H R
authors.initials: HR
authors.lastname: Khouja
authors.affiliation: Department of Life Sciences and Systems Biology, University of Torino, Viale Mattioli 25, 10125 Torino, Italy. Electronic address: stefania.daghino@unito.it.
authors.forename: S
authors.initials: S
authors.lastname: Daghino
authors.affiliation: IPSP - Istituto per la Protezione Sostenibile delle Piante CNR, Strada delle Cacce 73, I-10135 Torino, Italy. Electronic address: s.abba@ivv.cnr.it.
authors.forename: S
authors.initials: S
authors.lastname: Abbà
authors.affiliation: Université de Lorraine, UMR-1136 Interactions Arbres Microorganismes, Faculté des Sciences et Technologies, BP 70239, F-54506 Vandoeuvre-lès-Nancy, France. Electronic address: boutaraa.fatima@laposte.net.
authors.forename: F
authors.initials: F
authors.lastname: Boutaraa
authors.affiliation: Université de Lorraine, UMR-1136 Interactions Arbres Microorganismes, Faculté des Sciences et Technologies, BP 70239, F-54506 Vandoeuvre-lès-Nancy, France; Laboratoire Chrono-Environnement, UMR 6249, Université de Franche-Comté, Pôle Universitaire du Pays de Montbéliard, 4 Place Tharradin, BP 71427, 25 211 Montbéliard, France. Electronic address: michel.chalot@univ-fcomte.fr.
authors.forename: M
authors.initials: M
authors.lastname: Chalot
authors.affiliation: Université de Lorraine, UMR-1136 Interactions Arbres Microorganismes, Faculté des Sciences et Technologies, BP 70239, F-54506 Vandoeuvre-lès-Nancy, France; Laboratoire Interdisciplinaire des Environnements Continentaux, UMR 7360 CNRS-Université de Lorraine, Faculté des Sciences et Technologies, Bld des Aiguillettes, BP 70239, 54506 Vandoeuvre-les-Nancy, France. Electronic address: damien.blaudez@univ-lorraine.fr.
authors.forename: D
authors.initials: D
authors.lastname: Blaudez
authors.affiliation: Department of Life Sciences and Systems Biology, University of Torino, Viale Mattioli 25, 10125 Torino, Italy. Electronic address: elena.martino@unito.it.
authors.forename: E
authors.initials: E
authors.lastname: Martino
authors.affiliation: Department of Life Sciences and Systems Biology, University of Torino, Viale Mattioli 25, 10125 Torino, Italy. Electronic address: silvia.perotto@unito.it.
authors.forename: S
authors.initials: S
authors.lastname: Perotto
mesh_terms: D064173:Anaphase-Promoting Complex-Cyclosome / Q000235:genetics* / Q000378:metabolism; D001203:Ascomycota / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D002104:Cadmium / Q000378:metabolism; D017353:Gene Deletion; D018086:Glutamate Dehydrogenase (NADP+) / Q000378:metabolism; D005970:Glutamate Synthase / Q000235:genetics* / Q000378:metabolism; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D053858:Metabolic Networks and Pathways; D038821:Mycorrhizae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D018384:Oxidative Stress; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D014170:Transformation, Genetic; D029800:Vaccinium myrtillus / Q000382:microbiology; D015032:Zinc / Q000378:metabolism*
chemical_list: D021122:Protein Subunits; D002104:Cadmium; D005970:Glutamate Synthase; D018086:Glutamate Dehydrogenase (NADP+); D064173:Anaphase-Promoting Complex-Cyclosome; D005974:Glutamate-Ammonia Ligase; D015032:Zinc; D009584:Nitrogen
keywords: Glutamate synthase; Glutamine synthetase; Heavy metal tolerance; Insertional mutagenesis; Mycorrhizal fungi; Nitrogen metabolism