Multimerization of IAA3 via ROS suppresses lateral root formation in air gaps

Root growth and branching is strongly tuned to environmental conditions including soil compaction, nutrient availability, and the presence of water, with auxin having a major role in regulating root architecture. Here, Roy et al. have demonstrated how auxin contributes to a suppression of root branching in a dry region, which is known as xerobranching (from the Greek word xēros, meaning dry). The authors showed that reactive oxygen species (ROS) accumulate in air-gap tissues, and mutants in reactive oxygen production (rboh mutants) fail to suppress branching in air gaps and show lower levels of ROS in the air-gap tissues. They hypothesized that the transcriptional repressor IAA3, a key regulator of root branching, was responsible for the xerobranching, and they found that in the presence of ROS, IAA3 forms multimers, leading to the suppression auxin-responsive genes. Thus, the air-gap is signaled by ROS accumulation in root nuclei, which suppresses the formation of lateral roots in these dry regions. (Summary by Mary Williams @PlantTeaching.bsky.social) Science 10.1126/science.adu1470