H2O2 regulates root system architecture by modulating the polar transport and redistribution of auxin

The accumulation and redistribution of the plant hormone auxin plays a crucial role in root development and patterning. Plants can alter their root system architecture (RSA) to adapt to different biotic and abiotic stresses. In addition, reactive oxygen species (ROS), such as H2O2, are known to increase in plants undergoing stress. Here, we present evidence that H2O2 can regulate auxin accumulation and redistribution through modulating polar auxin transport, leading to changes in RSA. Plants exposed to different concentrations of H2O2 formed a highly branched root system with abundant lateral roots and a shorter primary root. Monitoring of the auxin responsive DR5::GUS indicated that auxin accumulation decreased in lateral root primordia (LRP) and emerging lateral root tips. In addition, polar auxin transport, including both basipetal and acropetal transport modulated by AUX1 and PIN protein carriers, was involved in the process. Taken together, our results suggest that H2O2 could regulate plastic RSA by perturbing polar auxin transport as a means of modulating the accumulation and distribution of auxin.