Arrest, Senescence, and Death of Shoot Apical Stem Cells in Arabidopsis thaliana.

Shoot stem cells act as the source of the aboveground parts of flowering plants. A precise regulatory basis is required to ensure that plant stem cells show the right status during stages of proliferation, senescence and cell death. Over the past decades, the genetic circuits controlling stem cell fate, including the regulatory pathways of establishment, maintenance, and differentiation, have been largely revealed. However, the morphological changes and molecular mechanisms of the final stages of stem cells, which are represented by senescence and cell death, have been less studied. The senescence and death of shoot stem cells are under the control of a complex series of pathways that integrate multiple internal and external signals. Given the crucial roles of shoot stem cells in influencing plant longevity and crop yields, researchers have attempted to uncover details of stem cell senescence and death. Recent studies indicate that stem cell activity arrest is controlled by the FRUITFULL (FUL)-APETALA2 (AP2) pathway and the plant hormones auxin and cytokinin, while the features of senescent and dead shoot apical stem cells have also been described, with dynamic changes in reactive oxygen species (ROS) implicated in stem cell death. In this review, we highlight the recent breakthroughs that have enriched our understanding of senescence and cell death processes in plant stem cells.