Abstract
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.
Highlights
Roots determine the amount of nutrients and water available for plant growth and development, direct impacting yield and other agriculturally important traits
Our genetic analysis of OsYUC overexpression lines and the taa1/fib1 mutants demonstrated that auxin synthesized by the TAA/YUC pathway is necessary and sufficient for crown root development in rice
We further showed that auxin-induced crown root initiation and elongation are mediated by the transcription factor WOX11, establishing a YUC-Auxin-WOX11 module for crown root development in rice
Summary
Roots determine the amount of nutrients and water available for plant growth and development, direct impacting yield and other agriculturally important traits. Because of its agronomic importance, rice root system has been studied extensively using both genetic and genomic approaches. The emerging picture is that auxin plays an essential role in almost every aspect of rice root growth and development. Disruption of auxin biosynthesis, metabolism, transport, or signaling has a profound impact on rice root development. Genetic screens for mutants that display altered patterns and/or morphology of root systems identified multiple loci (Mai et al, 2014). Molecular cloning and characterization of the rice root mutants clearly demonstrated the essential roles of auxin in root development. Gain-of-function mutations in the domain II of OsIAA11 and OsIAA13, which encodes negative
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