OsIAA23-mediated auxin signaling defines postembryonic maintenance of QC in rice.

Although the quiescent center (QC) is crucial to root development, the molecular mechanisms that regulate its postembryonic maintenance remain obscure. In this study, a semi-dominant mutant that exhibits pleiotropic defects in root tissues, which includes the root cap, lateral and crown roots, was isolated. The mutant is characterized by a loss of QC identity during postembryonic development, and the displayed defects result from a stabilizing mutation in domain II of OsIAA23 (Os06g39590). Expression of OsIAA23 is specific to the QC of the root tip during the development of primary, lateral and crown roots. Consistent with OsIAA23 expression in the QC, the auxin signaling marked by DR5p::GUS (ß-glucuronidase) was absent in the QC region of Osiaa23. Transgenic rice plants harboring Osiaa23 under the control of the QHB promoter mimic partially the defects of Osiaa23. These results indicate that the maintenance of the QC is dependent on OsIAA23-mediated auxin signaling in the QC. These findings provide insight into Aux/IAA-based auxin signaling during postembryonic maintenance of the QC in plants.