Arabidopsis ZUOTIN RELATED FACTOR1 Proteins Are Required for Proper Embryonic and Post-Embryonic Root Development.

Donghong Chen,Ying Ruan,Jing Feng,Wen-Hui Shen,Qiannan Wang

doi:10.3389/fpls.2019.01498

Abstract

The H2A/UBIQUITIN-binding proteins AtZRF1a/b have been reported as key regulators involved in multiple processes of Arabidopsis plant growth and development. Yet, the cellular and molecular mechanisms underlying the mutant phenotype remain largely elusive. Here we show that loss-of-function of AtZRF1a/b causes defective root elongation and deformed root apical meristem organization in seedlings. The premature termination of the primary root in the atzrf1a;atzrf1b double mutant is associated with an advanced onset of endoreduplication and subsequent consumption of reservoir stem cells. Cytological analyses using cell type-specific markers and florescent dyes indicate that AtZRF1a/b are involved in maintenance of proper cell layer organization, determinacy of cell identity, and establishment of auxin gradient and maximum at the root tip. During embryogenesis AtZRF1a/b act dominantly in regulating the maintenance of ground tissue initial cells and production of lateral root cap. Lastly, quantitative real-time polymerase chain reaction analysis shows mis-expression of some key genes involved in regulating cell patterning, cell proliferation and/or hormone pathways. Our results provide important insight into AtZRF1a/b function in cell fate determinacy and in establishment and maintenance of proper stem cell reservoir during embryonic and post-embryonic root development.

Highlights

The Arabidopsis root has a well-organized structure with simple longitudinal organization and few well-defined cell lineages, providing an excellent model system to investigate asymmetric cell division and cell fate determinacy
We demonstrated that AtZRF1a/b play crucial roles in regulating stem cell activity, cell layer organization, cell fate determinacy and cell division orientation in root apical meristem (RAM) during embryonic and post-embryonic root development
Hereinafter we focused on primary roots to investigate AtZRF1a/b function

Summary

Introduction

The Arabidopsis root has a well-organized structure with simple longitudinal organization and few well-defined cell lineages, providing an excellent model system to investigate asymmetric cell division and cell fate determinacy. In Arabidopsis (Arabidopsis thaliana) root proliferation domain, four types of initial stem cells surrounding approximately four quiescent center (QC) cells (Scheres et al, 1994), AtZRF1 Function in Root Development together constitute the stem cell niche (SCN). Within the root SCN, QC cells with slowly mitotic activity provide a reservoir for maintenance and replenishment of the surrounding initial stem cells, which exhibit high frequency of cell divisions (Heyman et al, 2013). These ascribed basic RAM cell pattern has been originally established during embryogenesis and maintained during postembryonic primary root growth (Dolan et al, 1993; Scheres et al, 1994)

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Results

Conclusion