Plant proteasome mediates a novel defense strategy against bacterial pathogens

Abstract

Plants have developed their own defense strategies, because they have no immune cells. Here we provide a novel mechanism underlying cell-autonomous immunity, which involves the fusion of membranes of a large-central-vacuole with the plasma membrane, resulting in the discharge of vacuolar antibacterial proteins to the outside of the cells where bacteria proliferate. The extracellular fluid that was discharged from the vacuoles of infected leaves had both antibacterial activity and cell-death-inducing activity. Membrane fusion was triggered in a proteasome-dependent manner by the bacterial infection. This novel membrane fusion-based defense strategy provides plants with a mechanism for attacking extracellular bacterial pathogens.