PROTECTION OF TELOMERES 1b safeguards the Arabidopsis genome by regulating ROS homeostasis

PROTECTION OF TELOMERES 1 (POT1) is a highly conserved telomere protein, essential for chromosome integrity and telomeric DNA replication. Arabidopsis thaliana encodes two divergent POT1 paralogs: AtPOT1a stimulates telomerase activity, but AtPOT1b function is unknown.

Here we show that AtPOT1b modulates reactive oxygen species (ROS) homeostasis. Oxidative stress induces AtPOT1b expression and telomeric accumulation, while AtPOT1b inactivation elevates ROS, increases telomeric and genome-wide oxidation, and causes stochastic telomere length changes. To address how AtPOT1b controls ROS, we report its localization in nuclei and peroxisomes, and association with catalases and peroxidases that enhance ROS scavenging.