Programmed cell death is a fundamental cellular process leading to the actively organized demise
of a cell. In comparison to animal apoptosis, the most prominent PCD type in animals, only little
is known about the molecular regulation of PCD in plants. Nevertheless, multiple instances of cell
death occur during plant development and during the plants responses to the biotic and abiotic
environment, and the correct initiation and execution of PCD is crucial for plant growth,
reproduction, and fitness.
We investigate the molecular regulation of PCD during vegetative and generative plant
development. One of our model systems is the Arabidopsis root cap, a plant organ that
unsheathes the meristematic stem cells at the root tip. Unlike other plant organs, the root cap
shows a rapid cellular turnover, balancing constant cell generation by specific stem cells with the
disposal of differentiated cells at the root cap edge. This cellular turnover is critical for the
maintenance of root cap size and its position around the growing root tip.
Recently, we could show that a highly organized cell death program is the final step of lateral root
cap differentiation and that preparation for cell death is transcriptionally controlled by
ANAC033/SOMBRERO. Precise timing of cell death is critical for the elimination of root cap cells
before they fully enter the root elongation zone, which in turn is important in order to allow optimal
root growth. Root cap cell death is followed by a rapid cell-autonomous corpse clearance and
DNA fragmentation dependent on the S1-P1 type nuclease BFN1. Based on these results, we
propose a novel concept in plant development that recognizes programmed cell death as a
mechanism for maintaining organ size and tissue homeostasis in the Arabidopsis root cap.