Plant science : an international journal of experimental plant biologyAug 21, 2026

Circadian clock proteins PRR influence root hair growth through the RHD6/RSL pathway in Arabidopsis

Circadian Biology Weekly Brief ↗PubMed ↗DOI ↗

Updated Aug 22, 2026

Abstract

The simultaneous disruption of PRR5, PRR7, and PRR9 results in defective root hairs in Arabidopsis thaliana.

PRR5, a protein associated with the circadian clock, interacts with key transcription factors RHD6 and RSL1 that are crucial for initiating root hairs.
Overexpression of PRR5 leads to significant increases in both the density and length of root hairs.
PRR proteins are implicated in enhancing the expression of RHD6, RSL1, and several downstream genes related to root hair development.
PRR5's role in promoting root hair growth necessitates the presence of RHD6 and RSL1.
PRR proteins also play a role in root hair development when plants are subjected to phosphate deficiency and salt stress.

Simplified

Root hairs, derived from trichoblasts, are critical for plant growth and environmental adaptation. Although environmental cues are known to influence root hair development, how endogenous timing systems such as the circadian clock integrate into the core transcriptional network governing root hair formation remains unclear. Here, we show that the circadian clock-associated protein PSEUDO-RESPONSE REGULATOR5 (PRR5) physically interacts with ROOT HAIR DEFECTIVE6 (RHD6) and RHD6 LIKE1 (RSL1), two basic helix-loop-helix transcription factors essential for root hair initiation. Genetic analyses suggest that PRR proteins contribute to root hair development under long-day conditions in Arabidopsis thaliana. Simultaneous disruption of PRR5, PRR7, and PRR9 results in defective root hairs, whereas PRR5 overexpression markedly increases root hair density and length. Transcriptomic and RT-qPCR analyses reveal that PRRs enhance the expression of RHD6, RSL1, and multiple downstream root hair-responsive genes, while modulating their temporal expression patterns. Furthermore, PRR5-mediated root hair promotion requires RHD6/RSL1, and PRR proteins enhance RHD6-dependent activation of the RSL4 promoter. PRRs also contribute to root hair development under phosphate-deficient and salt-stress conditions. Together, these findings establish a molecular framework in which PRR proteins regulate the RHD6/RSL network to coordinate root hair development and environmental responses.

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Circadian clock proteins PRR influence root hair growth through the RHD6/RSL pathway in Arabidopsis

Abstract

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