ABSTRACT During the life cycle of plants, the demise of certain cells occurs when they have fulfilled their task. This selective and tightly regulated adaptive mechanism, known as programmed cell death (PCD), contributes to life and is fundamental for the maintenance of cellular homeostasis. Proteases are one of the key performers of PCD-mediated processes and, although no caspases have been identified in plants, caspase-like activities are associated with PCD in different tissues, including developing seeds. The role of caspase-like proteases was first demonstrated with the identification of their phylogenetically closest proteins in plants, the metacaspases. Autophagy, which regulates different forms of PCD and plays key roles in cellular homeostasis, has been recently conceptualized as a mediator of life and death. Thus, autophagy genes are key determinants during this cellular suicide response. Although great advances have been made in the study of PCD, the molecular signals that trigger it remain unknown. Taken together, this review, referred to as the role of metacaspases and autophagy in PCD, illustrates the complexity and diversity of mechanisms that control PCD in plants.
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