Programmed cell death (PCD) is integral to development and health of animals and plants. In contrast to animals, however, the mechanisms involved in regulating PCD execution in plants remain insufficiently understood. Recent insights from the Arabidopsis root cap, a model system for developmentally controlled PCD, demonstrate that mitochondria disintegrate at the onset of PCD execution, releasing mitochondrial matrix proteins into the cytosol. As key regulators of animal subroutines are not conserved in plants, this finding suggests that mitochondrial disintegration is the result of convergent evolution in PCD pathways. Preliminary investigations have revealed a novel, hitherto uncharacterized plant protein that causes mitochondrial disintegration during plant PCD execution. In the proposed project, we will test the hypothesis that this pathway fulfils analogous functions to the well-established BAX-dependent intrinsic apoptotic pathway. We will do this by functionally analyzing the novel protein and the physiological context under which it operates. We aim to uncover the cell physiological and molecular mechanisms, and the role of mitochondrial disintegration, during the execution of developmentally controlled PCD in plants. The outcome of the proposed project has the potential to achieve a long-awaited breakthrough in our understanding of the mitochondrial mechanisms during plant PCD execution.