CRL6, a member of the CHD protein family, is required for crown root development in rice.

The root system in monocotyledonous plants is largely composed of postembryonic shoot-borne roots named crown roots, which are important for nutrients and water uptake. The molecular mechanism underlying regulation of crown root development is not fully explored. In this study, we characterized a rice (Oryza sativa) mutant defective in crown root formation, designated as crown rootless6 (crl6). Histological analysis showed that CRL6 influences crown root formation by regulating primordial initiation and development. Map-based cloning and subsequent complementation tests verified that the CRL6 gene encodes a member of the large chromodomain, helicase/ATPase, and DNA-binding domain (CHD) family protein. Realtime RT-PCR analysis showed that CRL6 was most highly expressed in the stem base region where crown roots initiated. In addition, auxin-action inhibited phenotype was observed during crl6 development. The expressions of OsIAA genes were down-regulated in crl6. Our results provide evidence that CRL6 plays an important role in crown root development in rice via auxin-related signaling pathway.