OsIAA8-OsARF12 module regulates deep rooting in rice by modulating expression of auxin transport genes

Deep rooting is an important factor affecting rice drought avoidance. However, few genes that control this trait have been identified in rice. In the present work, we cloned a gene, OsIAA8, associated with a rice quantitative trait locus for deep rooting. Overexpression of OsIAA8 increased deep rooting and yield under drought stress. OsIAA8, which encodes an Aux/IAA protein, interacts with auxin response factor OsARF12, and osarfl2 mutant plants also displayed increased deep rooting. The expression of several auxin transport genes (e.g., OsPIN2 and OsPIN8) was down-regulated in OsIAA8-overexpressing rice plants. OsARF12 promotes the transcription of these genes, whereas OsIAA8 inhibited this transcription activation. Furthermore, the auxin content in the roots of OsIAA8-overexpressing plants was reduced compared with wild type plants. Of five haplotypes at the OsIAA8 locus, accessions carrying Hap 2 had higher deep rooting. This study revealed that OsIAA8-OsARF12 module regulates deep rooting by inhibiting auxin transport, providing the insights into improvement of root architecture and drought resistance in rice breeding.