Trends in Plant Science
Volume 20, Issue 10, October 2015, Pages 601-603
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WOX5 is Shining in the Root Stem Cell Niche

https://doi.org/10.1016/j.tplants.2015.08.009Get rights and content

The WUS-RELATED HOMEOBOX 5 (WOX5) gene is expressed in the quiescent center (QC) to regulate the columella stem cell (CSC) identity. Three recent reports not only show how WOX5 is controlled but also highlight the key role of WOX5 in root stem cell niche maintenance.

Section snippets

WOX5 is a Root Stem Cell Organizer

In higher plants, the root is an important organ system for nutrient uptake, anchorage, and storage. Its growth depends on the continuous division of cells in the root meristem. At the tip of root apical meristem, a pool of stem cells, which are defined by the ability to renew themselves and contribute undifferentiated daughter cells to produce new tissues, surround a small group of organizing cells, the quiescent center (QC) [1]. Laser ablation experiments showed that root stem cells rapidly

Effector Genes Mediates WOX5 Function in the Stem Cell Niche

Using a WOX5 translational reporter line (pWOX5:WOX5-GFP) which could completely rescue the CSC defective phenotype of the wox5-1 mutant, Pi et al. showed that WOX5 protein accumulates not only in the QC but also in the CSCs [7]. This finding indicates that the mobile WOX5 protein may be at least part of the long-sought after QC signals that are controlling CSCs, a mechanism that has been hypothesized from laser ablation experiments [2]. By employing mRNA profiling assays, the authors

Precise Control of WOX5 Through Epigenetic Modifications

It has been reported that auxin acts through AUXIN RESPONSE FACTOR 10 (ARF10) and ARF16 to repress and confine WOX5 expression in the QC cells and thereby promote the differentiation of CSC daughter cells [10]. However, the upstream regulatory mechanisms controlling WOX5 expression was largely unknown. Recently, Zhang et al. found that the REPRESSOR OF WUSCHEL1 (ROW1), also called BARD1, directly binds to the WOX5 promoter region and restricts its transcription to the QC [9]. Genetic analysis

Concluding Remarks and Open Questions

In summary, three recent studies 7, 8, 9 not only represent a significant step toward understanding the regulation of WOX5 expression and its action mechanisms in the root but also uncover the central role of WOX5 in the maintenance of CSC identity (Figure 1). Nevertheless, there are some open questions still awaiting to be addressed. For example, how is the movement of WOX5 from the QC into the CSCs controlled? Which of the WOX5 targets are involved in the inhibition of cell differentiation in

Acknowledgments

Z.D. was supported by grants from the Ministry of Science and Technology of China (2015CB942901), the National Natural Science Foundation of China (Projects 31270327, 31470371, and 31222005), Shandong Provincial Funds for Distinguished Young Scholars (2014JQ201408). X.K. was supported by a grant from the National Natural Science Foundation of China (No. 31500227). H.T. was supported by a grant from the National Natural Science Foundation of China (No. 31500229). We also thank the anonymous

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