Sensing the dry: Redox-regulated auxin repression shapes root plasticity

Root architecture is crucial for plant survival under drought, yet how water stress signals shape root development has remained unclear. Recently, Roy et al. ( Science ) revealed that drought-induced accumulation of reactive oxygen species (ROS) in root nuclei triggers the auxin repressor IAA3 to form complexes (multimerization) that enable the recruitment of the co-repressor TOPLESS (TPL), thereby suppressing auxin signaling and blocking lateral root initiation. ROS signaling acts rapidly, within minutes of water deprivation, compared to slower ABA responses, allowing plants to quickly adjust lateral root growth. This discovery reveals a new redox–hormone regulatory mechanism that enables plants to fine-tune root branching during transient drought. Beyond advancing our understanding of adaptive root responses, these insights highlight potential molecular targets for developing crops with improved resilience under water limitation. • Drought-induced ROS signaling drives a redox-dependent repression of lateral root initiation • Nuclear ROS promote multimerization of the auxin repressor IAA3, enabling TPL recruitment • Integration of redox and hormonal pathways fine-tunes root architecture under transient drought