An RbohC and RbohE-mediated ROS oscillatory circuit regulates root cap turnover in Arabidopsis

As the primary interface between the growing root and the soil, the root tip experiences continuous mechanical and environmental stress. The root cap protects this region through dynamic turnover, in which outer cells are regularly shed and replaced by new cells derived from inner initials. This turnover proceeds via two distinct pathways: programmed cell death in the lateral root cap and detachment of the outermost columella root cap. Focusing on the latter, we show that reactive oxygen species (ROS) levels oscillate within the columella during its developmental cycle in Arabidopsis thaliana. The disruption of these oscillations through chemical inhibitors or exogenous ROS impairs columella initial division and detachment. We identify RbohC and RbohE as major ROS producers, negatively regulated by the NAC transcription factor ANAC33/SOMBRERO. ROS oscillations also affect auxin distribution by modulating the transporter PIN-FORMED2. These findings reveal a redox-based mechanism integrating ROS and auxin signaling to coordinate columella root cap turnover.