How plants respond to stress: Joining up the dots of the Map kinase signalling pathway

For the adaptation and survival of plants, sensing of stress signals and their transduction into appropriate responses is crucial. MAP kinase pathways play key roles in cellular responses towards extracellular signals. The Arabidopsis MPK4 signal transduction pathway, composed of MEKK1, MKK1/MKK2 and MPK4, shares biotic and abiotic inputs and also has multiple outputs. This pathway has been well studied at the genetic and biochemical level, but relatively little is known about the dynamics and interactions of the proteins within the cell, and what differentiates a biotic from an abiotic response in terms of protein localization and interaction. This project aims to gain some insights of the dynamics of MPK4 pathway proteins by fluorescently tagging them and visualizing the stable transgenic Arabidopsis. Confocal laser scanning microscopy study revealed that under basal condition, all four members of this pathway are associated with the plasma membrane. Our data suggest that after biotic stress, MEKK1 and MPK4 proteins rapidly translocate from the plasma membrane, in associated with vesicles that bud off the plasma membrane to the nucleus. Dynamics of these vesicle-trafficking and protein-protein interaction has to be investigated in plants. These experiments illuminate the complexities of MAP kinase signalling in plants.