Understanding stem cell regulatory circuits is the next challenge in plant biology, as these cells are essential for tissue growth and organ regeneration in response to stress. In the Arabidopsis primary root apex, stem cell-specific transcription factors BRAVO and WOX5 co-localize in the quiescent centre (QC) cells, where they commonly repress cell division so that these cells can act as a reservoir to replenish surrounding stem cells, yet their molecular connection remains unknown. Genetic and biochemical analysis indicates that BRAVO and WOX5 form a transcription factor complex that modulates gene expression in the QC cells to preserve overall root growth and architecture. Furthermore, by using mathematical modelling we establish that BRAVO uses the WOX5/BRAVO complex to promote WOX5 activity in the stem cells. Our results unveil the importance of transcriptional regulatory circuits in plant stem cell development.
SUMMARYRoot growth and development are essential features for plant survival and the preservation of terrestrial ecosystems. In the Arabidopsis primary root apex, stem-cell specific transcription factors BRAVO and WOX5 co-localize at the Quiescent Center (QC) cells, where they repress cell division so that these cells can act as a reservoir to replenish surrounding stem cells, yet their molecular connection remains unknown. Here, by using empirical evidence and mathematical modeling, we establish the precise regulatory and molecular interactions between BRAVO and WOX5. We found that BRAVO and WOX5 regulate each other besides forming a transcription factor complex in the QC necessary to preserve overall root growth and architecture. Our results unveil the importance of transcriptional regulatory circuits at the quiescent and stem cells to the control of organ initiation and growth of plant tissues.
In animals and plants, stem-cell niches are local microenvironments that are tightly regulated to preserve their unique identity while communicating with adjacent cells that will give rise to specialized cell types. In the primary root of Arabidopsis thaliana, two transcription factors, BRAVO and WOX5, among others, are expressed in the stem-cell niche. Intriguingly, BRAVO, a repressor of quiescent center divisions, confines its own gene expression to the stem-cell niche, as evidenced in a bravo mutant background. Here, we propose through mathematical modeling that BRAVO confines its own expression domain to the stem-cell niche by attenuating a WOX5-dependent diffusible activator of BRAVO. This negative feedback drives WOX5 activity to be spatially restricted as well. The results show that WOX5 diffusion and sequestration by binding to BRAVO are sufficient to drive the experimentally observed confined BRAVO expression at the stem-cell niche. We propose that the attenuation of a diffusible activator can be a general mechanism acting at other stem-cell niches to spatially confine genetic activity to a small region while maintaining signaling within them and with the surrounding cells.
The specification of rhizoid precursor cells in the epidermis of Marchantia polymorpha gemmae has been shown to involve lateral inhibition mediated by the microRNA FRH1, which represses its activator RSL1, a rhizoid-specific transcription factor. However, how inhibition is conferred to adjacent cells and which is the mechanism underlying the emergence of rhizoid precursors remain unknown. In this paper, we use mathematical and computational modeling to show that the previously reported rhizoid patterns in WT, gain-of-function, and loss-of-function mutants of FRH1 and RSL1 are consistent with lateral inhibition mediated by a mobile FRH1. Our modeling results suggest that cells in Marchantia wild-type gemmae reside close to a critical state, where diffusion of FRH1 drives a switch of RSL1 expression that specifies rhizoid precursors. This process involves an initially random trigger and subsequent lateral inhibition, leading to cellular patterns consisting of small and filamentous clusters of rhizoid precursors. We confirm these predictions with new data on WT rhizoid distributions. Our findings highlight a novel mechanism of cellular pattern formation, opening new research directions for understanding cellular differentiation and tissue morphogenesis, with potential implications for a broad range of biological systems.
Stem cell niches are local microenvironments that preserve their unique identity while communicating with adjacent tissues. In the primary root of Arabidopsis thaliana, the stem cell niche comprises the expression of two transcription factors, BRAVO and WOX5, among others. Intriguingly, these proteins confine their own gene expression to the niche, as evidenced in each mutant background. Here we propose through mathematical modeling that BRAVO confines its own expression domain to the stem cell niche by attenuating its WOX5-dependent diffusible activator. This negative feedback drives WOX5 action to be spatially restricted as well. The results show that WOX5 diffusion and sequestration by binding to BRAVO is sufficient to drive realistic confined BRAVO expression at the stem cell niche. We propose that attenuation of a diffusible activator can be a general mechanism to confine genetic activity to a small region while at the same time maintain signaling within it and with the surrounding cells.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.