title: Inhibition of nitrogen fixation in symbiotic Medicago truncatula upon Cd exposure is a local process involving leghaemoglobin.
abstract: Leguminous biological nitrogen fixation (BNF) is very sensitive to environmental fluctuations. It is still contentious how BNF is regulated under stress conditions. The local or systemic control of BNF and the role played by reactive oxygen species (ROS) in such regulation have still not been elucidated completely. Cadmium, which belongs to the so-called heavy metals, is one of the most toxic substances released into the environment. The mechanisms involved in Cd toxicity are still not completely understood but the overproduction of ROS is one of its characteristic symptoms. In this work, we used a split-root system approach to study nodule BNF and the antioxidant machinery's response to the application of a mild Cd treatment on one side of a nodulated Medicago truncatula root system. Cd induced the majority of nodule antioxidants without generating any oxidative damage. Cd treatment also provoked BNF inhibition exclusively in nodules directly exposed to Cd, without provoking any effect on plant shoot biomass or chlorophyll content. The overall data suggest that the decline in BNF was not due to a generalized breakdown of the plant but to control exerted through leghaemoglobin/oxygen availability, affecting nitrogenase function.
authors.affiliation: Interactions Biotiques et Santé Végétale UMR INRA 1301 - CNRS 6243 - Université de Nice - Sophia Antipolis, 400 Route des Chappes, BP 167, F-06903 Sophia Antipolis Cedex, France.
authors.forename: Daniel
authors.initials: D
authors.lastname: Marino
authors.forename: Isabelle
authors.initials: I
authors.lastname: Damiani
authors.forename: Sébastien
authors.initials: S
authors.lastname: Gucciardo
authors.forename: Iker
authors.initials: I
authors.lastname: Mijangos
authors.forename: Nicolas
authors.initials: N
authors.lastname: Pauly
authors.forename: Alain
authors.initials: A
authors.lastname: Puppo
mesh_terms: D000975:Antioxidants / Q000378:metabolism; D002104:Cadmium / Q000378:metabolism / Q000633:toxicity*; D007874:Leghemoglobin / Q000378:metabolism*; D046913:Medicago truncatula / Q000187:drug effects* / Q000378:metabolism; D009586:Nitrogen Fixation / Q000187:drug effects*; D035261:Plant Components, Aerial / Q000187:drug effects; D053204:Root Nodules, Plant / Q000187:drug effects* / Q000378:metabolism; D013559:Symbiosis / Q000187:drug effects
chemical_list: D000975:Antioxidants; D007874:Leghemoglobin; D002104:Cadmium
keywords: Antioxidant; Medicago truncatula–Sinorhizobium meliloti symbiosis; cadmium; nitrogen fixation; reactive oxygen species; split-root system.