Temporal changes in cell division rate and genotoxic stress tolerance in quiescent center cells of Arabidopsis primary root apical meristem

Rupak Timilsina,Hong Gil Nam,Jin Hee Kim,Hye Ryun Woo

doi:10.1038/s41598-019-40383-2

Rupak Timilsina, Hong Gil Nam + Show 2 more

Open Access

https://doi.org/10.1038/s41598-019-40383-2

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Abstract

Plant roots provide structural support and absorb nutrients and water; therefore, their proper development and function are critical for plant survival. Extensive studies on the early stage of ontogenesis of the primary root have revealed that the root apical meristem (RAM) undergoes dynamic structural and organizational changes during early germination. Quiescent center (QC) cells, a group of slowly dividing cells at the center of the stem-cell niche, are vital for proper function and maintenance of the RAM. However, temporal aspects of molecular and cellular changes in QC cells and their regulatory mechanisms have not been well studied. In the present study, we investigated temporal changes in QC cell size, expression of QC cell-specific markers (WOX5 and QC25), and genotoxic tolerance and division rate of QC cells in the Arabidopsis primary root. Our data revealed the decreased size of QC cells and the decreased expression of the QC cell-specific markers with root age. We also found that QC cell division frequency increased with root age. Furthermore, our study provides evidence supporting the link between the transition of QC cells from a mitotically quiescent state to the frequently dividing state and the decrease in tolerance to genotoxic stress.

Highlights

Roots are vital plant organs that provide an anchorage for the plant’s aerial parts, as well as absorb nutrients and water; the proper development and function of roots are essential for plant survival[1,2,3]
As the first step to characterize temporal changes in the properties of Quiescent center (QC) cells, we examined size of QC cells at 4, 8, and 12 days after planting (DAP)
We examined the possibility that the genes involved in DNA damage response and repair, such as ATAXIA TELANGIECTASIA MUTATED (ATM), ATM AND RAD3-RELATED (ATR)[17], and SUPPRESSOR OF GAMMA RESPONSE 1 (SOG1)[46], regulate chromosomal segregation during QC cell division because the stem cell initials carrying loss-of-function mutations in these genes were reported to be resistant to cell death upon genotoxin treatment

Summary

Introduction

Roots are vital plant organs that provide an anchorage for the plant’s aerial parts, as well as absorb nutrients and water; the proper development and function of roots are essential for plant survival[1,2,3]. The cells in the SCN are sub-divided into mitotically inactive quiescent center (QC) cells and surrounding actively proliferating stem cell initials, namely, columella initials, cortex and endodermis initials, vascular initials, and stele initials[1,4,7,10,11,12]. Since the vast majority of studies involving the QC cells in Arabidopsis have been focused on a particular time window of early root development, usually from 4 to 7 days after germination[12,13,16,18,30], our knowledge of the regulatory mechanisms underlying the establishment and maintenance of the QC cells as the root ages is still fragmentary. We performed temporal analysis of cell size, expression of QC cell-specific markers as well as genotoxic tolerance and division rate of QC cells, in the Arabidopsis primary root. Our data revealed dynamic temporal changes in size and regulatory gene expressions and an inverse correlation between the division rate and the tolerance to genotoxic stress of QC cells

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