Differential patterns of reactive oxygen species and antioxidative mechanisms during atrazine injury and sucrose-induced tolerance in Arabidopsis thaliana plantlets.

http://www.biomedcentral.com/1471-2229/9/28International audienceBackground: Besides being essential for plant structure and metabolism, soluble carbohydrates play important roles in stress responses. Sucrose has been shown to confer to Arabidopsis seedlings a high level of tolerance to the herbicide atrazine, which causes reactive oxygen species (ROS) production and oxidative stress. The effects of atrazine and of exogenous sucrose on ROS patterns and ROS-scavenging systems were studied. Simultaneous analysis of ROS contents, expression of ROS-related genes and activities of ROS-scavenging enzymes gave an integrative view of physiological state and detoxifying potential under conditions of sensitivity or tolerance. Results: Toxicity of atrazine could be related to inefficient activation of singlet oxygen (1O2) quenching pathways leading to 1O2 accumulation. Atrazine treatment also increased hydrogen peroxide (H2O2) content, while reducing gene expressions and enzymatic activities related to two major H2O2-detoxification pathways. Conversely, sucrose-protected plantlets in the presence of atrazine exhibited efficient 1O2 quenching, low 1O2 accumulation and active H2O2-detoxifying systems. Conclusion: In conclusion, sucrose protection was in part due to activation of specific ROS scavenging systems with consequent reduction of oxidative damages. Importance of ROS combination and potential interferences of sucrose, xenobiotic and ROS signalling pathways are discussed

Metabolic profiling of Lolium perenne shows functional integration of metabolic responses to diverse subtoxic conditions of chemical stress

International audiencePlant communities are confronted with a great variety of environmental chemical stresses. Characterization of chemical stress in higher plants has often been focused on single or closely related stressors under acute exposure, or restricted to a selective number of molecular targets. In order to understand plant functioning under chemical stress conditions close to environmental pollution conditions, the C3 grass Lolium perenne was subjected to a panel of different chemical stressors (pesticide, pesticide degradation compound, polycyclic aromatic hydrocarbon, and heavy metal) under conditions of seed-level or root-level subtoxic exposure. Physiological and metabolic profiling analysis on roots and shoots revealed that all of these subtoxic chemical stresses resulted in discrete physiological perturbations and complex metabolic shifts. These metabolic shifts involved stressor-specific effects, indicating multilevel mechanisms of action, such as the effects of glyphosate and its degradation product aminomethylphosphonic acid on quinate levels. They also involved major generic effects that linked all of the subtoxic chemical stresses with major modifications of nitrogen metabolism, especially affecting asparagine, and of photorespiration, especially affecting alanine and glycerate. Stress-related physiological effects and metabolic adjustments were shown to be integrated through a complex network of metabolic correlations converging on Asn, Leu, Ser, and glucose-6-phosphate, which could potentially be modulated by differential dynamics and interconversion of soluble sugars (sucrose, trehalose, fructose, and glucose). Underlying metabolic, regulatory, and signalling mechanisms linking these subtoxic chemical stresses with a generic impact on nitrogen metabolism and photorespiration are discussed in relation to carbohydrate and low-energy sensing

Implications of field margin plant communities in the environmental dynamics of pesticides pollutions

Plusieurs textes réglementaires européens et nationaux préconisent des dispositifs de zones-tampons végétalisées pour contrôler ou empêcher la contamination des écosystèmes par les pollutions agricoles. L’implication spécifique des communautés végétales qui font partie de la structure même de ces zones-tampons sera analysée dans le contexte des pollutions engendrées par les pesticides d’origine agricole. La distribution des contaminations environnementales par les pesticides et leurs produits associés ou dérivés démontre que les communautés végétales des zones-tampons péri-agricoles sont confrontées à des stress chimiques et xénobiotiques fluctuants et complexes, caractérisés entre autres par des expositions à des mélanges de faibles doses de polluants. Les implications physiques et microbiologiques de l’action des plantes sur la dynamique environnementale des contaminations par les pesticides sont bien comprises. Mais les plantes présentent aussi des capacités de réponse efficace aux stress chimiques et xénobiotiques et une réelle capacité de phytoremédiation des polluants. Cependant, les rôles phytoremédiateurs directs des plantes des zones-tampons végétalisées restent mal évalués, et les interférences affectant cette capacité de phytoremédiation ne sont pas non plus bien comprises. Il est donc nécessaire que des études intégratives prennent en compte la diversité des contaminants, la diversité des espèces végétales utilisées dans les zones-tampons, leur potentiel de réponses aux xénobiotiques organiques en conditions contrôlées de laboratoire, et leur comportement écophysiologique en conditions réelles de terrain. De telles études permettront d’optimiser les capacités d’épuration des zones-tampons en fonction des modalités de contamination et des combinaisons de polluants.Several types of regulations, at the European and national levels, advocate setting up vegetative buffer strips in order to control or prevent the contamination of ecosystems by agricultural pollutions. The specific implication of the plant communities that are part of the make-up of buffer zones will be assessed in the context of agriculture-linked pollutions by pesticides. The distribution of environmental contaminations involving pesticides and associated products shows that plant communities of vegetative buffer strips are confronted with chemical and xenobiotic stresses that show great fluctuations and complexity, with, among other characteristics, exposures to mixtures of low levels of pollutants. The physical and microbiological dimensions of plant action on the environmental dynamics of contaminating pesticides are well understood, but higher plants are also capable of efficient responses to chemical and xenobiotic stresses and of phytoremediation of pollutants. However, the direct phytoremediating roles of plants in vegetative buffer-zones have remained poorly appreciated, and the interferences that affect this capacity for phytoremediation are not fully understood either. It is therefore essential that integrative studies take into account the diversity of contaminants, the diversity of plant species that are used in buffer zones, their capacity to respond to organic xenobiotics under laboratory controlled conditions, and their ecophysiological behaviour under real field conditions. Such studies will be useful to optimize the depollution capacities of buffer zones in relation with the various modalities of contamination and combinations of pollutants

Genome-wide interacting effects of sucrose and herbicide-mediated stress in Arabidopsis thaliana: novel insights into atrazine toxicity and sucrose-induced tolerance

<p>Abstract</p> <p>Background</p> <p>Soluble sugars, which play a central role in plant structure and metabolism, are also involved in the responses to a number of stresses, and act as metabolite signalling molecules that activate specific or hormone-crosstalk transduction pathways. The different roles of exogenous sucrose in the tolerance of <it>Arabidopsis thaliana </it>plantlets to the herbicide atrazine and oxidative stress were studied by a transcriptomic approach using CATMA arrays.</p> <p>Results</p> <p>Parallel situations of xenobiotic stress and sucrose-induced tolerance in the presence of atrazine, of sucrose, and of sucrose plus atrazine were compared. These approaches revealed that atrazine affected gene expression and therefore seedling physiology at a much larger scale than previously described, with potential impairment of protein translation and of reactive-oxygen-species (ROS) defence mechanisms. Correlatively, sucrose-induced protection against atrazine injury was associated with important modifications of gene expression related to ROS defence mechanisms and repair mechanisms. These protection-related changes of gene expression did not result only from the effects of sucrose itself, but from combined effects of sucrose and atrazine, thus strongly suggesting important interactions of sucrose and xenobiotic signalling or of sucrose and ROS signalling.</p> <p>Conclusion</p> <p>These interactions resulted in characteristic differential expression of gene families such as ascorbate peroxidases, glutathione-S-transferases and cytochrome P450s, and in the early induction of an original set of transcription factors. These genes used as molecular markers will eventually be of great importance in the context of xenobiotic tolerance and phytoremediation.</p

Carbon Dynamics, Development and Stress Responses in Arabidopsis: Involvement of the APL4 Subunit of ADP-Glucose Pyrophosphorylase (Starch Synthesis)

An Arabidopsis thaliana T-DNA insertional mutant was identified and characterized for enhanced tolerance to the singlet-oxygen-generating herbicide atrazine in comparison to wild-type. This enhanced atrazine tolerance mutant was shown to be affected in the promoter structure and in the regulation of expression of the APL4 isoform of ADP-glucose pyrophosphorylase, a key enzyme of the starch biosynthesis pathway, thus resulting in decrease of APL4 mRNA levels. The impact of this regulatory mutation was confirmed by the analysis of an independent T-DNA insertional mutant also affected in the promoter of the APL4 gene. The resulting tissue-specific modifications of carbon partitioning in plantlets and the effects on plantlet growth and stress tolerance point out to specific and non-redundant roles of APL4 in root carbon dynamics, shoot-root relationships and sink regulations of photosynthesis. Given the effects of exogenous sugar treatments and of endogenous sugar levels on atrazine tolerance in wild-type Arabidopsis plantlets, atrazine tolerance of this apl4 mutant is discussed in terms of perception of carbon status and of investment of sugar allocation in xenobiotic and oxidative stress responses

Plasticité physiologique et moléculaire de la tolérance aux xénobiotiques et de la capacité de phytoremédiation chez arabidopsis thaliana

Les sucres solubles exogènes induisent, chez Arabidopsis thaliana, une forte tolérance à l'atrazine. Cette tolérance est liée à l'activation de mécanismes de défense contre le stress oxydatif généré par l'atrazine, à une dérépression des gènes associés à la photosynthèse et probablement à une induction de voies de détoxification de l'atrazine. L'étude d'un mutant affecté dans la voie de biosynthèse de l'amidon a permis de démontrer que les mécanismes de tolérance à l'atrazine pouvaient également être induits par des modifications de l'allocation du carbone et par conséquent des niveaux de sucres endogènes dans les plantules. Comme les plantes tolérantes accumulaient l'herbicide dans leurs tissus, des expérimentations à l'échelle du microcosme de sol ont montré que l'induction de tolérance à l'atrazine par application de sucre exogène pourrait permettre des applications innovantes en biotechnologie de l'environnement.RENNES1-BU Sciences Philo (352382102) / SudocRENNES-Géosciences (352382209) / SudocSudocFranceF

Effect of environmentally realistic doses of pesticides on tritrophic interactions in grass strips

International audienc

Effect of environmentally realistic doses of pesticides on tritrophic interactions in grass strips

International audienc

Plasticité physiologique et moléculaire de la tolérance aux xénobiotiques et de la capacité de phytoremédiation chez arabidopsis thaliana

Les sucres solubles exogènes induisent, chez Arabidopsis thaliana, une forte tolérance à l'atrazine. Cette tolérance est liée à l'activation de mécanismes de défense contre le stress oxydatif généré par l'atrazine, à une dérépression des gènes associés à la photosynthèse et probablement à une induction de voies de détoxification de l'atrazine. L'étude d'un mutant affecté dans la voie de biosynthèse de l'amidon a permis de démontrer que les mécanismes de tolérance à l'atrazine pouvaient également être induits par des modifications de l'allocation du carbone et par conséquent des niveaux de sucres endogènes dans les plantules. Comme les plantes tolérantes accumulaient l'herbicide dans leurs tissus, des expérimentations à l'échelle du microcosme de sol ont montré que l'induction de tolérance à l'atrazine par application de sucre exogène pourrait permettre des applications innovantes en biotechnologie de l'environnement.RENNES1-BU Sciences Philo (352382102) / SudocRENNES-Géosciences (352382209) / SudocSudocFranceF

DEMEETER : Dispositif Expérimental de Modulation du niveau d’Eau dans les Ecosystèmes TERrestres, un outil de recherche et de démonstration

National audienc