Abstract
Plants are known to have a type of programmed cell death (PCD) to defend against invading pathogens. We show that following a bacterial attack, the proteasome β1 subunit (PBA1) mediates fusion of the vacuolar and cell membranes. This process results in the discharge of vacuolar proteins to the outside of the plasma membrane. This then leads to PCD for the efficient disease resistance. To our knowledge, this is the first report of fusion of the vacuolar and cell membranes in plants. PCD may be induced by the release of vacuolar hydrolytic enzymes as a result of the PBA1-dependent membrane fusion. Fusion of the membranes may also release vacuolar defense proteins to kill bacteria on the outside of the cells.
