It is common knowledge that an ethernet connection is safer than a wireless connection, and cellular organelles share this approach. To communicate directly with each other, organelles are thought to use Membrane Contact Sites (MCS), the “optical fibers” at the intracellular level. Organelles are key stress sensors due to their tight integration into the cell’s metabolic networks, and inter-organelle communication is crucial to maintain cellular homeostasis. I hypothesise that MCS allow fast and efficient communication of stress signals between organelles to coordinate the plant cell’s stress response. However, the organelle tethering proteins, the stimuli driving MCS formation and the signalling events mediated via these MCS remain elusive in plants. This project will provide insight into the role of ER-mitochondria communication in response to stress in Arabidopsis thaliana. For that, I will exploit ER-mitochondria interacting proteins previously established in the host lab to set up a proteomic screen to identify novel players involved in ER-mitochondria MCS in plants. In addition, I will develop a high-throughput platform to study inter-organelle interactions in vivo and to identify stimuli perturbing MCS dynamics. Finally, I will employ genetic perturbation to study the function of ER-mitochondria MCS in stress signalling. This project will shed light on plant inter-organelle communication and will contribute to the fundamental understanding of plant stress responses.