OsIAA23-mediated Auxin Signaling Defines Postembryonic Maintenance Of QC In Primary Roots In Rice (Oryza Sativa L.)

Quiescent Center (QC) cells are the most important cells to maintain the nearby stem cells, which are crucial for the meristem activity. Of all the cells in the root apex, QC has a peak in auxin concentration, however, the role of auxin in QC is still not clear.Here we report a gain-of-function mutant with defects in the formation of lateral root, adventitious root and the maintenance of QC in postembryonic development. As a distal organizer in the root apex, the disappearance of the QC consequently results in the vanishing of the root cap and the termination of root growth. Map-based cloning revealed that the pleiotropic mutated traits in roots were caused by a single nucleotide substitution of OsIAA23, causing a single amino acid change in the conserved core sequence in the domain II, which is crucial for its degradation. The stabilized Osiaa23would block the auxin signaling pathway and cause auxin response defects. Although the expression of OsIAA23was detected in all the tissues examined by RT-PCR and in transgenic plants of OsIAA23p::GUS and OsIAA23p::Osiaa23:GFP, the expression of OsIAA23was defined specifically in QC in root apex. In line with its specific expression in QC, we didn't detect the DR5::GUS staining in QC region of the mutant.To determine the function of OsIAA23in the maintanence of QC, transgenic rice harboring Osiaa23via QHB promoter was developed. The transgenic rice showed similar disordered QC structure with that of Osiaa23.Our research highlights the importance of auxin signaling in the maintenance of QC, and OsIAA23is participated in the auxin signaling of QC in the postembryonic development.