Regulation and physiological integration of salt stress signaling and adaptation in Arabidopsis

Basic data for this project

Description

Salt stress in form of elevated sodium (Na+) concentrations in the soil is a major abiotic stress which adversely affects plant growth and crop yield. Plants developed elaborate mechanisms to sense and adapt to this stress. Central to plant salinity sensing and adaptation is the so called salt overly sensitive (SOS) pathway. Here, the calcium sensor SOS3/CBL4 likely deciphers salt stress induced Ca2+ signals and activates the kinase SOS2/CIPK24 upon direct interaction. Consequently, this Ca2+ sensor-kinase complex activates the H+/Na+ antiporter SOS1 for Na+ extrusion. In the context of Na+ stress the occurrence of Ca2+ signals and the adaptive regulation of pH homeostasis and H+ fluxes via AHA-PM ATPases have been well documented. However, how these H+ pumps are regulated and how they are interconnected with the SOS pathway remains to be investigated. Moreover, while the core-pathway for salt tolerance has been described it is obvious that it needs to be intimately interconnected and integrated with all other plant regulatory circuits and signaling networks. However, elements of this interconnection are only beginning to emerge. In our preliminary work, both applicants recognized an enormous complexity of Ca2+ patterns that are formed during salt stress, identified alternative interactions of SOS2/CIPK24 with distinct Ca2+ sensors as regulatory switches in salt responses, uncovered multiple phosphorylation of SOS2/CIPK24 as a likely integration mechanism for the SOS pathway and identified direct regulatory interactions between CBLs/CIPKs with the AHA2 H+ pump. Based on our preliminary data the proposed project specifically aims to address:1. The analysis of salt induced Ca2+ signals from the cellular to the organismic level and the characterization of their function and interconnection with other signaling systems. 2. The regulation of the kinase SOS2 by protein-protein interactions and transphosphorylation and its integration with other signaling processes.3. The identification and characterization of novel components contributing to salt tolerance by modulating the SOS pathway.4. The investigation of components interconnecting Ca2+ signaling and regulating AHA H+-ATPase activity for proton/pH regulation in plant salt tolerance By combining our reverse-genetic resources, newly generated reporter lines and complementary expertise and by using a combination of cell-biological approaches and in vivo molecular phenotype analyses, we intend to identify critical components and to characterize fundamental molecular mechanisms that mediate the integration of plant salt stress responses with plant developmental plasticity and physiological homeostasis.