Nuclear dismantling events: Crucial steps during the execution of plant programmed cell death

Abstract

Programmed cell death (PCD) is an important process in the life cycle of multicellular organisms, which has the relevant function of eliminating unneeded or damaged cells. In response to either internal or external signals, cells that will undergo PCD begin a degenerative process in which the nucleus becomes the major target of the machinery of cell death. In this review, we summarize the key features that characterize nucleus dismantling in plant cells undergoing PCD, focusing on the similarities and differences with their animal counterparts. Taking into account morphological and biochemical events, two types of nuclear dismantling processes may be distinguished, termed premortem and postmortem, depending on whether nucleus degeneration begins before or after vacuolar rupture and rapid clearance of the cell contents. Premortem nucleus dismantling includes events affecting the nuclear envelope (such as lobbing of the nuclear surface, selective proteolysis of nucleoporins, and nuclear pore complex clustering), chromatin condensation, and DNA fragmentation. The postmortem process is so rapid that a sequence of events during cellular disintegration has not been identified. Finally, critical targets that may be of relevance in nuclear dismantling research in the future are discussed.