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Réponses écophysiologiques et moléculaires des plantes aux stress xénobiotiques complexes de faible intensité : implications dans les capacités de protection environnementale des bandes enherbées

Abstract : Environmental pollutions by xenobiotics, especially by pesticides and heavy metals derived from agricultural activities, show an important complexity of chemical composition and of spatiotemporal dynamic. Vegetative filter strips between cultivated fields and streams limit the diffusion of these residual pollutions to natural environments. However, the exact biological role of plant in these buffer strips is poorly understood in this context of environmental and ecological protection. A comparative study carried out in situ and in controlled conditions highlighted the role of plant compartment in the processes of absorption, storage and/or partial degradation of pollutants in planta. Such capability of phytoremediation depends on the maintenance of a vegetal cover in area subjected to recurring flow of pesticides, it varies according to species and leads to the structuration of vegetative filter strip communities. An integrative study in controlled conditions of plant responses to low doses of pollutants allowed to analyze at different levels of complexity the impacts of chemical stresses on the model species Arabidopsis thaliana and the grassland species Lolium perenne. Low and sublethal doses of xenobiotics, associated degradation products and heavy metals induced cryptic perturbations at metabolic and molecular levels. Multi-pollution analyses, which reflect realistic conditions of environmental exposure, highlighted complex interactive effects between pollutants in mixture and the difficulty to predict them. The mechanisms of response to these chemical stresses differ according to the species and the pollutant, and suggest differences in term of perception and/or transport of pollutants, or of coordination of molecular and metabolic responses. Arabidopsis presented a coordination of its responses toward an increase of stress metabolites, a decrease of carbon metabolites (soluble carbohydrates), in parallel with modifications of gene expressions implicated on antioxidant defences, defence against xenobiotic stresses, or phytohormone dynamic. Chemical stress leads to major modifications of nitrogen metabolism in Lolium, and perturbations of processes of photorespiration. De novo transcriptomic analysis of Lolium therefore showed that a majority of identified genes are related to signal transduction pathways, highlighting the complexity of response mechanisms and the links between metabolic signals, especially linked to carbohydrate, hormonal signaling pathways, stress signals and photosynthesis. Subtoxic chemical stress induced cryptic re-engineering of plant processes that may explain the development of tolerance for some species and their persistence in area affected by residual pollution.
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https://tel.archives-ouvertes.fr/tel-01187712
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Submitted on : Thursday, August 27, 2015 - 2:02:14 PM
Last modification on : Friday, June 3, 2022 - 3:27:49 AM
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Anne-Antonella Serra. Réponses écophysiologiques et moléculaires des plantes aux stress xénobiotiques complexes de faible intensité : implications dans les capacités de protection environnementale des bandes enherbées. Biologie végétale. Université Rennes 1, 2015. Français. ⟨NNT : 2015REN1S005⟩. ⟨tel-01187712⟩

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