Reactive oxygen species production and signalling as a component of salinity tolerance mechanism in cereals

Reactive Oxygen Species (ROS) are highly reactive and toxic by-products of the aerobic metabolism, which are overproduced during period of stress. They disturb the cell machinery and induce oxidative damages on important biological macromolecules. Salinity is one of those major abiotic stresses, which affects considerably the growth rate and limits crop productivity. To enhance salinity stress tolerance and find strategies which would cope with global issues related to the rise of salt-affected lands and global food demand, various investigations have been performed. They did mainly focus on the understanding of physiological traits and ion homeostasis responses. However, oxidative stress is also a key part of the plant response to stress, but is still under-investigated. An efficient oxidative stress tolerance mechanism may induce significant improvement in salinity resistance. Nevertheless, recent studies have suggested that ROS play a dual role in cells, both as toxic by-products and as key molecules in complex signalling networks: ROS are essential actors which could influence the expression and regulation of various genes to control many processes, including the stress response. In this project, the production of two ROS, hydrogen peroxide and superoxide, was investigated in roots from various species and genotypes, respectively by DCF-DA and DHE fluorescence. The study gave a basic framework about ROS kinetics accumulation in roots depending on time of exposure to different salt concentrations. Specificities related to growth conditions, plant age and root tissues were also investigated. It was demonstrated that, compared to wheat and even more to pea, barley has a better ability to handle salinity, thanks to a rapid and transient oxidative burst. The aim of this work was also to link the oxidative stress with salinity stress tolerance, which had been investigated in previous studies. Two main conclusions can be drawn from this project: (i) there is a clear correlation between ROS accumulation and K+ leaking studied in previous experiments; (ii) ROS have a significant implication in the signal transduction network. Knowledge about the main mechanisms involved in oxidative stress tolerance and signalling can give a better background in the development of plants with improved salinity tolerance and find adapted solutions to this growing concern.