Differential responses to salt-induced oxidative stress in three phylogenetically related plant species: <em>Arabidopsis thaliana</em> (glycophyte), <em>Thellungiella salsuginea</em> and <em>Cakile maritima</em> (halophytes). Involvement of ROS and NO in the control of K+/Na+ homeostasis

Salinity, which is usually associated with a nitro-oxidative stress component, is one of the major environmental factors limiting plant growth and development. Plants have thus developed specific ways of dealing with this problem. The compartmentalization of sodium (Na+) ions in vacuoles and the capacity to sharply discriminate between potassium (K+) and Na+ in order to maintain high K+/Na+ ratios are two of the most effective strategies to overcome salt stress. Plants require large amounts of K+ to maximize growth and yields. This macronutrient is involved in physiological processes such as growth, photosynthesis, osmoregulation, enzyme activation, stomatal movement, water and nutrient transport via the xylem and protein synthesis. Resistance to salt stress is mainly related to the capacity of plants to maintain improved K+ uptake despite competition from Na+. The Brassicaceae family includes species such as Arabidopsis thaliana (plant model for glycophytes), Thellungiella salsuginea and Cakile maritima (plant models for halophytes), which exhibit significant variations in response to salt stress. In this review, we provide a comprehensive update with respect to differential responses to salt stress in these three plant species, with particular emphasis on the potential involvement of reactive oxygen species (ROS) and nitric oxide (NO) in maintaining K+/Na+ homeostasis and their contribution to salt tolerance

Glyphosate-induced oxidative stress in Arabidopsis thaliana affecting peroxisomal metabolism and triggers activity in the oxidative phase of the pentose phosphate pathway (OxPPP) involved in NADPH generation

Glyphosate is a broad-spectrum systemic herbicide used worldwide. In susceptible plants, glyphosate affects the shikimate pathway and reduces aromatic amino acid synthesis. Using Arabidopsis seedlings grown in the presence of 20 μM glyphosate, we analyzed H2O2, ascorbate, glutathione (GSH) and protein oxidation content as well as antioxidant catalase, superoxide dismutase (SOD) and ascorbate-glutathione cycle enzyme activity. We also examined the principal NADPH-generating system components, including glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase (6PGDH), NADP-malic enzyme (NADP-ME) and NADP-isocitrate dehydrogenase (NADP-ICDH). Glyphosate caused a drastic reduction in growth parameters and an increase in protein oxidation. The herbicide also resulted in an overall increase in GSH content, antioxidant enzyme activity (catalase and all enzymatic components of the ascorbate-glutathione cycle) in addition to the two oxidative phase enzymes, G6PDH and 6PGDH, in the pentose phosphate pathway involved in NADPH generation. In this study, we provide new evidence on the participation of G6PDH and 6PGDH in the response to oxidative stress induced by glyphosate in Arabidopsis, in which peroxisomal enzymes, such as catalase and glycolate oxidase, are positively affected. We suggest that the NADPH provided by the oxidative phase of the pentose phosphate pathway (OxPPP) should serve to maintain glutathione reductase (GR) activity, thus preserving and regenerating the intracellular GSH pool under glyphosate-induced stress. It is particularly remarkable that the 6PGDH activity was unaffected by pro-oxidant and nitrating molecules such as H202, nitric oxide or peroxynitrite