The Role of PP2C Phosphatase in the Negative Regulation of the Stress-Induced MAPK Pathway in Arabidopsis Thaliana

Plants are able to adapt to environmental stresses (wounding, drought, pathogens, etc.) by expressing specific sets of genes, but little is understood how plants sense and transmit these environmental signals to intrinsic responses. We have identified a specific stress-induced signalling pathway in Medicago involving the activation of protein kinases and a PP2C-type protein phosphatase MP2C as a negative regulator of this pathway. My studies show that MP2C is a direct inhibitor of the stress-activated protein kinase in vitro and in plant extracts. The present proposal aims to understand how this PP2C-type phosphatase regulates the stress-induced signal transduction pathway in isolated cells and intact plants. I will test the hypothesis that this phosphatase is part of a negative feedback loop functioning to inactivate this pathway by 1.) expression of various signal transduction cascade components in plant cells, 2) connecting the stress-induced protein kinase pathway to phosphatase gene expression, 3) determining the biological functions of this phosphatase in stress signalling in plants. An understanding of the stress signal transduction mechanism is not only of scientific interest but is essential for improving stress resistance in plants by employing their inbuilt capacity to adapt to environmental stresses.