The quiescent center and root regeneration

Abstract

Since its discovery by F.A.L Clowes, extensive research has been dedicated to identifying the functions of the quiescent center (QC). One of the earliest hypotheses was that it serves a key role in regeneration of the root meristem. Recent works provide support for this hypothesis and began to elucidate the molecular mechanisms underlying this phenomenon. There are two scenarios to consider when assessing the role of the QC in regeneration. One, when the damage leaves the QC intact, and the other, when the QC itself is destroyed. In the first scenario, multiple factors are recruited to activate QC cell division in order to replace damaged cells, but whether the QC has a role in the second scenario is less clear. Using both gene expression studies and following cell division pattern has shown that the QC is assembled gradually, only to appear as a coherent identity late in regeneration. Similar late emergence of the QC was observed during the de novo formation of the lateral root meristem. These observations can lead to the conclusion that the QC has no role in regeneration. However, activities normally occurring in QC cells, such as local auxin biosynthesis, are still found during regeneration but occur in different cells in the regenerating meristem. Thus, we explore an alternative hypothesis, that following destruction of the QC, QC-related gene activity is temporarily distributed to other cells in the regenerating meristem, only coalesce into a distinct cell identity when regeneration is complete.

WITHDRAWN: Reversible phosphorylation of WOX5 protein controls the homeostasis of QC

“…It is widely known that the WOX5 protein expresses in the QC cells and maintains their quiescence from the embryonic stage to the postembryonic stage (Celine et al, 2014; Haecker et al, 2004). However, QC cells are not in a strictly quiescent state (G0 stage) but in a resting state (G1 stage) with very low proliferative activity, these resting QC cells can re-enter the cell cycle when needed (Clowes, 1968; Matosevich and Efroni, 2021; Ubogoeva et al, 2021). How accurately define the low proliferative activity of QC is unclear.…”

Maintenance of stem cell activity in plant development and stress responses

“…This experimental evidence highlights the pivotal role of QC-delivered stem cell-promoting signals, which are effective within a certain range of cell diameters and typically diminish in cells not in direct contact with the QC. Therefore, the QC-delivered stem cell-promoting signal represents the essential pathway for stem cell maintenance in Arabidopsis thaliana root tips ( Dubrovsky and Ivanov, 2021 ; Matosevich and Efroni, 2021 ; Strotmann and Stahl, 2021 ; Zhai et al., 2023 ).…”

BRAVO self-confined expression through WOX5 in the Arabidopsis root stem-cell niche

“…WOX5 itself has been proposed to act as the long-sought short-range signal to repress columella stem cell differentiation ( Pi et al, 2015 ), albeit recent results challenge this view ( Berckmans et al, 2020 ). Although short-range signaling is thought to ensure that stem-cell numbers are restrained and the SCN does not become displaced from the growing root tip, it is yet unclear how this is achieved ( Matosevich and Efroni, 2021 ; Rahni et al, 2016 ; Scheres, 2007 ).

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