sigNal · Novel insights into the sensing of salt stress in plants: understanding the relationship between salt stress response and cytosolic pH changes.

Novel insights into the sensing of salt stress in plants: understanding the relationship between salt stress response and cytosolic pH changes.

Soil salinisation is a growing problem for agriculture worldwide. Evidence is available at the physiological and molecular levels that Na is the major cause of salt toxicity in most species. The Salt Overly Sensitive (SOS) pathway is one of the main regulatory systems responsible for Na homeostasis in plants. The SOS pathway is activated by salt stress and comprises three core components: SOS1, SOS2 and SOS3. SOS3 (CBL4) is a calcium (Ca) sensor with four Ca-binding sites (EF-Hand domains) that perceives the increase of intracellular Ca triggered by salt stress, recruits SOS2 (CIPK24) and the SOS2–SOS3 complex activates the downstream target protein SOS1 (NHX7). Cytosolic free Ca is a common second messenger in the signalling of a variety of abiotic stresses. Current thinking is that the specificity of Ca signalling is determined by the different patterns of cytosolic Ca level changes, often referred to as the “Ca signatures”, that are elicited by the stimulus. However, such a wide range of Ca-activated responses lead us to posit the existence of additional mechanisms relaying input signals that, together with this Ca signature, would initiate the specific response for a particular stress. In this context, the overall aim of sigNal project was to gain novel insights into the early steps in the sensing and regulation of the salt stress response, for a better understanding of the salinity tolerance mechanisms of plants. In particular, I tried to show how salt stress signalling is discriminated from other biotic and abiotic stresses also leading to Ca spikes. There are two main conclusions of this project: (1) salt stress promote an increase of cytosolic pH in the root tip, higher than the one observed under the same osmotic stress and high enough to be consider as having multiple cell consequences; (2) root tip works as a stress-sensing niche (SSN), were combination of stress-specific changes of pH and Ca, would be responsanble for the activation of stress-specific responses.

Data: CORDIS, © European Union