Molecular mechanisms of AP2C1/2 in stress adaption

Plant defence responses to environmental stress are regulated by signalling pathways. The investigation of these pathways is currently an emerging research field with unresolved questions about the molecular mechanism of signal transduction and its link to the reaction of plants to stress. Future developments of sustainable agricultural practice require breeding of plants with enhanced innate immunity to pathogens using new molecular markers for important regulators of plant stress responses. Mitogen-activated protein kinases (MAPKs) provide prevalent signalling components in this process. Stress-activated MAPKs are modified through phosphorylation upon biotic and abiotic stresses. PP2C-type protein phosphatases are important to control the activity of MAPKs. Which PP2Cs and how control stress-activated MAPKs are not understood at present. To investigate if and how these negative regulators channel signalling pathways towards specific responses we suggest to study the model plant Arabidopsis with modified PP2C functions. In this way we will learn about the function, regulation, localization, interaction and regulatory targets of central protein kinase cascade controlling stress signalling pathways. As a whole, this work will substantially advance our molecular understanding of stress signal transduction mechanism and the plasticity plants show in adapting to environmental changes.

Plants are actively communicating with their environment. External signals are perceived by plant cells and transmitted within the cell to generate fast appropriate responses. These responses are essential for plant adaptation to unfavourable environmental conditions. To understand how signals are transmitted inside the cells we studied the model plant Arabidopsis thaliana. We show that signalling is ensured by protein phosphorylation in the very similar way as it happens in animals. Protein phosphatases play a major role in regulation of these processes. We found that novel phosphatases from Arabidopsis are responsible for plant environmental adaptation as well as for development. An important result giving a substantial impact to the cell signalling field was our finding that different protein phosphatases are inactivating the same signalling pathway during normal growth conditions. We demonstrated that during the absence of these phosphatases in the plant, its cells are sending stress signals and generating stress responses even in non-stress conditions. Another important finding demonstrates a role of a protein phosphatase in stomata development. Stomata are cells on plant surfaces performing water/gas exchange and thus crucial to keep the balance in our ecosystem. Our findings give more understanding about the mechanism of cellular signal transduction and provide the basis for deeper studies on regulation of signalling. Moreover, this knowledge can help to produce plants that are more effective in CO2 accumulation.