Title : H2O2 signature and antioxidative profile as key players of rice responses against salt stress
Abstract:
Plants are continuously faced with adverse environmental conditions, which affect the oxidative metabolism and photosynthetic efficiency, thus leading to the over-production of Reactive Oxygen Species (ROS). Despite their harmful nature, ROS also acts as powerful signalling molecules involved in responses to stress stimuli. A complex and differentiated redox network modulated by different environmental stimuli is responsible for the generation of ROS signature that is pivotal for the activation of homeostatic responses against stresses and for guaranteeing plant fitness in the resistant species or varieties.
According to the intensity and kind of stress, as well as plant developmental stage, resistant plants are able to maintain a normal phenotype by increasing detoxifying pathways (ROS – scavenging systems, molecular chaperons, compatible solutes etc.). In other cases, they can block cell division and growth in order to reduce the occurrence of genetic alterations that could negatively affect the progeny survival. Furthermore, Programmed Cell Death (PCD) of specific cellular districts is another defence strategy activated by tolerant/resistant plants in response to different abiotic stresses.
The comprehension of plant resistance mechanisms, defined at molecular, cellular and physiological level and activated in response to stress conditions related to climatic changes, represents a crucial area of plant science also due to its implications in food security. In fact, adverse climatic factors, such as drought, waves of temperatures far from the optimal ones and soil salinization drastically affects crop growth and productivity worldwide.
In this context, rice plays a central role since it is one of the main source of food for humans and is one of the most sensitive cereals to abiotic stresses, salinity first but also extreme temperatures and water scarcity.
In order to reach an advancement of knowledge regarding the signalling pathways triggering defence responses against salt stress two rice varieties showing contrasting salt sensitivity have been investigated. Analysis of key metabolites and related genes/enzymes have been performed on cell cultures derived from the two varieties, as well as on leaves and roots of the two varieties subjected to salt stresses of different intensity. An in-depth study centred on ascorbate and glutathione metabolism, cellular redox state and markers of cell viability and death has been carried out over treatment time. Moreover, redox-dependent regulatory mechanisms, such as post-translational modifications, i.e. thiol-disulphide switch, glutathionylation and S-nitrosylation, modulating enzyme activity and gene expressions, have been analysed in responses to salt stress.
These results wish to described ROS signatures and different antioxidative pathways as a part of a complex redox network activated in rice after salt stress exposure in order to draw effective strategies aimed at increasing rice resilience toward salt stress.
