Shedding the Last Layer: Mechanisms of Root Cap Cell Release.

Narender Kumar,Anjali S Iyer-Pascuzzi

doi:10.3390/plants9030308

Narender Kumar, Anjali S Iyer-Pascuzzi

Open Access

https://doi.org/10.3390/plants9030308

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Abstract

The root cap, a small tissue at the tip of the root, protects the root from environmental stress and functions in gravity perception. To perform its functions, the position and size of the root cap remains stable throughout root growth. This occurs due to constant root cap cell turnover, in which the last layer of the root cap is released, and new root cap cells are produced. Cells in the last root cap layer are known as border cells or border-like cells, and have important functions in root protection against bacterial and fungal pathogens. Despite the importance of root cap cell release to root health and plant growth, the mechanisms regulating this phenomenon are not well understood. Recent work identified several factors including transcription factors, auxin, and small peptides with roles in the production and release of root cap cells. Here, we review the involvement of the known players in root cap cell release, compare the release of border-like cells and border cells, and discuss the importance of root cap cell release to root health and survival.

Highlights

Unlike animals, plant cells are fixed and attached together at the cell wall
The root cap is located at the tip of the root and protects the root apical meristem (RAM), a zone of dividing cells that produces all cells in the root (Figure 1)
Because of the importance of root cap cell production to root cap cell release, we briefly review the transcription factors and peptides involved in cell production

Summary

Introduction

There are several developmental processes in which cell separation is required and critical for plant survival These include development of intercellular air spaces, leaf abscission, and seed dehiscence [1,2]. Another site of cell separation is the root cap, where the outer layer is sloughed off and released into the soil. In Arabidopsis and other Brassicaceae members including Brassica napus (rapeseed), Brassica oleracea (Brussels sprout), and Sinapis alba (Mustard), BCs are released from the root tip as an organized layer of several cells that remain attached and are called “border-like cells (BLCs)” [10,14] (Figure 1).

Schematic

Signaling Peptide and Transcriptional Regulation of BLC Release

The Role of Hormones in BLC Release

Variations in BC Release Among Species

BC and BLC Protective Functions in Biotic and Abiotic Stresses

Conclusions and Future Perspectives