Séminaire IBIP
Les séminaires ont lieu sur le Campus Montpellier SupAgro/INRA de La Gaillarde (2, place P. Viala Montpellier)

Jeudi 4 septembre 2014
Amphi 206 (Cœur d’école) à 14h

Metal-induced oxidative challenge: from perception and signal transduction to plant acclimation and growth

Tony Remans & Ann Cuypers
Centre for Environmental Sciences, Hasselt University, Belgium

Anthropogenic activities have led to high emissions of metals into the environment and a substantial number of areas worldwide are diffusely contaminated. There is a major concern in using these soils because plants are an important entry route of these toxic substances into the food chain. Nonetheless, bringing these lands back into sustainable use, for the production of energy biomass and industrial feedstock applications, can reduce detrimental environmental and socio-economic impacts. However, plants subjected to the toxic effects of metals show growth inhibition and the mechanisms of metal toxicity need to be understood to improve growth under these conditions. We use Arabidopsis thaliana as a model plant to investigate metal-induced stress signaling and responses. To reveal general and metal-specific mechanisms, we expose plants to metals with different properties to the plant: cadmium (Cd, non-essential and non-redox active), copper (Cu, essential micro-nutrient and redox-active) and zinc (Zn, essential but non-redoxactive). As such, we observed metal-specific reactions of root growth to excess Cd, Cu and Zn in Arabidopsis thaliana, that are indicative of the existence of metal-specific sensing and signalling pathways. We try to reveal these with forward genetics and reverse genetics approaches focused on the role of plant hormones. Since placement of roots is an important factor determining contact with metals and uptake, root architecture is an important factor for optimizing plant growth for phytoremediation (in which growth inhibition should be reduced to allow placement in contaminated soil patches), and in safe biomass production (in which root growth should be directed to less- or non-contaminated soil-patches). Once excess metals are taken up, their influence on the cellular redox state is an important determinant of metal phytotoxicity. Cu, as a redox-active element, can directly cause formation of ROS (reactive oxygen species), whereas this implies indirect pathways (e.g. via NADPHoxidases) under Cd stress. High levels of ROS may cause cellular oxidative damage and plant cells use their antioxidative defence system consisting of enzymes (e.g. superoxide dismutases) and antioxidant metabolites (e.g. glutathione and ascorbate) to counteract high ROS levels. On the other hand, ROS are also signaling molecules triggering plant responses. Because hydrogen peroxide (H2O2) production is an immediate response to Cd- or Cu-exposure, it might be a key molecule triggering signal transduction events during metal exposure. Multiple studies also emphasize the existence of extensive crosstalk between different signal transduction pathways in plant cells. We are therefore studying metal-stress induced signaling and anti-oxidative responses and use Arabidopsis mutants, e.g. affected in signalling (e.g. MAPKinase, ethylene signaling) or antioxidative defense, to reveal components of general and metal-specific molecular mechanisms.

Contact : Françoise Gosti

Contacts IBIP :
Sabine Zimmermann
Alexandre Martinière
Christine Granier
Chantal Baracco