Quiescent center initiation in the Arabidopsis lateral root primordia is dependent on the SCARECROW transcription factor

Abstract

Lateral root formation is an important determinant of root system architecture. In Arabidopsis, lateral roots originate from pericycle cells, which undergo a program of morphogenesis to generate a new lateral root meristem. Despite its importance for root meristem organization, the onset of quiescent center (QC) formation during lateral root morphogenesis remains unclear. Here, we used live 3D confocal imaging to monitor cell organization and identity acquisition during lateral root development. Our dynamic observations revealed an early morphogenesis phase and a late meristem formation phase as proposed in the bi-phasic growth model. Establishment of lateral root QCs coincided with this developmental phase transition. QC precursor cells originated from the outer layer of stage II lateral root primordia, within which the SCARECROW (SCR) transcription factor was specifically expressed. Disrupting SCR function abolished periclinal divisions in this lateral root primordia cell layer and perturbed the formation of QC precursor cells. We conclude that de novo QC establishment in lateral root primordia operates via SCR-mediated formative cell division and coincides with the developmental phase transition.

Root stem cell niche organizer specification by molecular convergence of PLETHORA and SCARECROW transcription factor modules

“…4B). PLT3, TCP20, and TCP21 fusion proteins were detected at stage I, whereas SCR expression was consistently observed in the stage II outer cell layer (Goh et al 2016;Du and Scheres 2017). Notably, WOX5 promoter activity was detected from stage II onward in cells where PLT, SCR, and TCP proteins are all expressed.…”

“…, and plt1- roots (Bennett and Scheres 2010;Hofhuis et al 2013;Tian et al 2014;Goh et al 2016;Du and Scheres 2017). During lateral root initiation, two to three adjacent pericycle cell files undergo several rounds of anticlinal divisions to create a single layered stage I lateral root primordium (LRP) composed of up to eight to 10 cells of equal size.…”

“…In the stage III LRP, the central cells act as QC progenitors based on fate mapping and the stable expression of WOX5 in these cells from that stage onward (Supplemental Fig. 4A; Ditengou et al 2008;Goh et al 2016;Rovere et al 2016).…”

Regulation of Hormonal Control, Cell Reprogramming, and Patterning during De Novo Root Organogenesis

“…To follow primordia formation, we used Pro WOX5 :GUS. WOX5 is expressed early during lateral root primordia formation (Tian et al, 2014;Goh et al, 2016), and also after root primordia initiation during de novo organogenesis Hu and Xu, 2016). Expression of Pro WOX5 :GUS was first detected at 4 dae in clusters of cells within the endogenous callus (Fig.…”

Lateral root initiation requires the sequential induction of transcription factors LBD16 and PUCHI in Arabidopsis thaliana

“…LR formation is initiated with nuclear migration toward the common cell wall of a pair of LR founder cells, followed by asymmetric anticlinal cell division (De Rybel et al ., ; Goh et al ., ). These asymmetric cell divisions produce two small daughter cells as well as two larger flanking cells that continue to undergo formative cell divisions to form the dome‐like LR primordium that eventually organizes into a new meristem (Malamy & Benfey, ; Goh et al ., ; von Wangenheim et al ., ). Genetic and physiological analyses have shown that most of the developmental events during LR formation (specification of LR founder cells, LR initiation, LR primordium development, and LR emergence) are regulated by auxin, and that multiple and distinct auxin signaling modules are involved in these developmental events (De Smet et al ., , ; Moreno‐Risueno et al ., ; Lavenus et al ., ; Xuan et al ., , ).…”