Do Plant Caspases Exist?

Programmed cell death (PCD) is a functional con- cept that refers to cell death that is part of the normal life of a multicellular organism; it involves controlled disassembly of the cell. In animal systems PCD is synonymous with apoptosis, a cell death process characterized by a distinct set of morphological and biochemical features, mediated by a class of specific Cys proteases called cysteinyl aspartate-specific pro- teinases (caspases). Although to date no functional homologs of animal caspases have been identified in plants, a vast amount of indirect evidence suggesting the existence in plants of true caspase-like activity and its functional involvement in plant cell death has accumulated.