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

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

Détection et quantification de l'oxygène singulet chez les plantes.

Communication oral

Signalling functions of soluble sugars in the protection of photosynthesis during xenobiotic stress in Arabidopsis thaliana.

communication invitéeNational audienc

Implication des sucres solubles dans les réponses aux stress xénobiotique et oxydatif chez Arabidopsis thaliana

Les sucres solubles, principalement, saccharose, glucose et fructose, jouent un rôle central dans la structure, le métabolisme et le fonctionnement des plantes. Ils sont de plus impliqués dans de nombreux mécanismes de réponse aux stress, biotiques ou abiotiques, où ils agissent non seulement en tant que métabolites, mais aussi en tant que signaux capables d activer des voies de signalisation aboutissant à des modifications d expression génétique. Leur implication dans les réponses aux stress xénobiotique et oxydatif a été étudiée chez la plante-modèle Arabidopsis thaliana en interaction avec des molécules polluantes, en particulier l atrazine, herbicide de la famille des triazines, qui a été prise comme polluant modèle générant un fort stress oxydatif. Les connaissances sur l induction de tolérance à l atrazine par le saccharose ont été systématisées par une approche transcriptomique couplée à des analyses biochimiques, génétiques, physiologiques et écophysiologiques. Il a été ainsi démontré que l atrazine provoquait, par des modifications d expression génétique, des perturbations importantes des systèmes de défense et de réparation. Ces effets négatifs étaient contrecarrés par le saccharose exogène, permettant un maintien ou une induction des systèmes de détoxication des espèces réactives de l oxygène et de réparation des dommages oxydatifs. De plus, des facteurs de transcription nécessaires à l activation de la tolérance par le saccharose ont été identifiés et partiellement caractérisés. Enfin, les effets d induction de tolérance ont été démontrés dans un contexte écophysiologique de fluctuations endogènes des sucres solubles dans diverses accessions d Arabidopsis, par une corrélation entre les teneurs en saccharose endogène et les variations de sensibilité à l atrazine, révélant ainsi l importance de l état nutritionnel et de l allocation du carbone dans les processus d acclimatation aux stress abiotiques chez les plantes.Soluble sugars, i.e. mainly sucrose, glucose and fructose, play a central role in the structure, metabolism and functioning of higher plants. They are also involved in responses to numerous biotic or abiotic stresses, where they act not only as metabolites, but also as signalling molecules that activate signal transduction pathways leading to important modifications of gene expression. Their involvement in the responses to xenobiotic and oxidative stress was studied in the model plant Arabidopsis thaliana in interaction with pollutant molecules, principally atrazine, an herbicide of the triazine family, which was used as a model pollutant causing severe oxidative stress. Sucrose-induced tolerance to atrazine stress was analysed by transcriptome profiling associated with further biochemical, genetic, physiological and ecophysiological studies. This resulted in the demonstration that atrazine induced modifications of gene expression leading to severe disturbances of defence and repair systems. These toxic effects were lifted by exogenous sucrose, which maintained or induced mechanisms of reactive oxygen species detoxication and of repairs of oxidative damage. Moreover, transcription factors that are necessary for the activation of sucrose-induced tolerance were identified and partially characterised. Finally, induction of tolerance was validated in the ecophysiological context of endogenous soluble sugar fluctuations in various accessions of Arabidopsis, through correlations between the levels of endogenous sucrose and variations of atrazine sensitivity, thus revealing the importance of nutritional status and carbon allocation in acclimation to abiotic stresses in plants.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF