RSL4-regulated transcription and ROP signaling coordinate root hair growth via BOUNDARY OF ROP DOMAIN proteins.
Xu M, Li YQ, Shi XL, Li LS, Hao GJ
Summary
7.8/10Plants coordinate root hair growth—tiny structures that absorb water and nutrients—by integrating a transcription factor (RSL4) with cellular signaling proteins (ROP). The research reveals that BDR proteins bridge these two pathways and create a self-reinforcing feedback loop, enabling precise spatial and temporal control of root hair development.
Key Findings
BDR6/7 proteins function as dual-targeted regulators, localizing to both the plasma membrane and nucleus to promote root hair initiation and growth
ROP signaling and RSL4 transcription are interdependent: ROP2-driven growth requires BDR6/7, and ROP signaling depends on RSL2/4 function
BDR6/7 and RSL4 form a positive feedback loop where BDR6/7 enhances RSL4 transcriptional activity while RSL4 regulates BDR6/7 gene expression
Original Abstract
In vascular plants, root hairs (RH) increase plant adaptability by facilitating the uptake of water and nutrients. RH initiation and elongation require the establishment and maintenance of cellular polarity. The ROOT HAIR DEFECTIVE6-LIKE (RSL) transcription factor RSL4 controls RH-specific gene expression and ROP GTPases direct polar growth, but how these pathways integrate to spatiotemporally orchestrate RH initiation and elongation remains unknown. We identify Arabidopsis BOUNDARY OF ROP DOMAIN (BDR) protein BDR6/7 as positive regulators of RH initiation and growth. BDR6/7 are targeted both to the plasma membrane (PM) and in the nucleus of RHs. By genetic approaches, we demonstrate that ROP signaling is essential for BDR6/7-promoted RH growth whereas ROP2-driven RH growth also requires BDR6/7. BDR6/7 associate and co-localize with RSL2/4 to nuclei in heterologous plant cells. Genetic dissections uncover an interdependency between BDR6/7 and RSL2/4. Indeed, BDR6/7 enhance RSL4-associated RHE reporter activity in protoplasts and support RSL4 binding at target promoters whereas RSL4 binds BDR6/7 promoters and is required for their expression, creating a positive feedback loop that may integrate transcriptional and signaling dynamics. Genetic evidence also supports the dependence of ROP signaling on RSL2/4. The dual-targeted BDR6/7, RSL2/4-mediated transcription, and apical PM-associated ROP signaling, may form a tripartite module, scaling developmental outputs for spatiotemporal coordination of plant cell morphogenesis.
Species Mentioned
Arabidopsis (rockcress) is a genus of small flowering plants in the cabbage and mustard family, Brassicaceae. Arabidopsis species are native to temperate and subarctic Eurasia and North America, North Africa, and the mountains of eastern tropical Africa. This genus is of great interest since it c...
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