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Updated: Jan 11, 2026

Lateral Root Inducible System in Arabidopsis and Maize
Published on: January 14, 2016
ELONGATED HYPOCOTYL5 and B-BOX21/22 are required for auxin-induced root hair development
Peirui Chen1, Deshun Lei1, Jinxi Jiang1
1G416, School of Life Sciences, Xiamen Key Laboratory of Plant Genetics and State Key Laboratory of Cellular Stress Biology, Xiang'an Campus, Xiamen University, Xiamen 361102, P. R. China.
Abstract:
Auxin is a key phytohormone required for root hair development. It acts as a central node that integrates various environmental and hormonal signals. Here, we report that the light signaling components HY5 (ELONGATED HYPOCOTYL 5) and BBX21/22 (B-box 21/22) are not only involved in light-enhanced root hair development but also required for auxin-induced root hair growth in Arabidopsis (Arabidopsis thaliana). Exogenous auxin increases HY5 protein levels in the root differentiation zone through reducing the level of nuclear-localized COP1 (CONSTITUTIVE PHOTOMORPHOGENIC 1), which targets HY5 protein for degradation. Both HY5 and BBX21/22 are required for auxin-induced expression of genes involved in root hair development, including key regulatory genes RSL4/5 (RHD6-LIKE 4/5). Through a transient expression assay, we demonstrated that co-expressing BBX21/22 and HY5 promotes the expression of the reporter gene driven by the RSL4/5 promoter. Genetic analysis revealed that HY5 and BBX21/22 act in the same pathway. Furthermore, this HY5-BBX21/22 module is also required for ethylene and low-phosphate-induced root hair growth. We thus propose that the HY5-BBX21/22 module acts as a key node downstream of auxin that potentially mediates the crosstalk between various environmental and hormonal signals in regulating root hair development.
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