UC San Diego

A well-developed root system in rice and other crops can ensure plants to efficiently absorb nutrients and water. Auxin is a key regulator for various aspect of root development, but the detailed molecular mechanisms by which auxin controls crown root development in rice are not understood. We show that overexpression of a YUC gene, which encodes the rate-limiting enzyme in auxin biosynthesis, causes massive proliferation of crown roots. On the other hand, we find that disruption of TAA1, which functions upstream of YUC genes, greatly reduces crown root development. We find that YUC overexpression-induced crown root proliferation requires the presence of the transcription factor WOX11. Moreover, the crown rootless phenotype of taa1 mutants was partially rescued by overexpression of WOX11. Furthermore, we show that WOX11 expression is induced in OsYUC1 overexpression lines, but is repressed in the taa1 mutants. Our results indicate that auxin synthesized by the TAA/YUC pathway is necessary and sufficient for crown root development in rice. Auxin activates WOX11 transcription, which subsequently drives crown root initiation and development, establishing the YUC-Auxin-WOX11 module for crown root development in rice.