Three-dimensional quantitative analysis of the Arabidopsis quiescent centre

Quiescent centre (QC) cells represent an integral part of the root stem cell niche. They typically display a low division frequency that has been reported to be controlled by hormone signaling and different regulators, including the ETHYLENE RESPONSE FACTOR 115 (ERF115) transcription factor and D-type cyclins. Here, we applied a three-dimensional (3D) imaging to visualize the Arabidopsis QC cell number, volume and division patterns, including visualization of anticlinal divisions that cannot be deduced from longitudinal 2D imaging. We found that 5-day-old seedlings possess on average eight QC cells which are organized in a monolayered disc. In a period of 7 d, half of the QC cells undergo anticlinal division in a largely invariant space. Ectopic expression of ERF115 and CYCLIN D1;1 (CYCD1;1) promote both anticlinal and periclinal QC cell divisions, the latter resulting in a dual-layered QC zone holding up to 2-fold more QC cells compared with the wild type. In contrast, application of cytokinin or ethylene results in an increase in the number of periclinal, but a decrease in anticlinal QC divisions, suggesting that they control the orientation of QC cell division. Our data illustrate the power of 3D visualization in revealing unexpected QC characteristics.

Automated summary

QC cells play a significant role in the root stem cell niche, and 3D imaging reveals their characteristics such as number, volume, and division patterns. The study found unexpected outcomes including the promotion of QC cell divisions by ERF115 and CYCD1;1, and the control of division orientation by cytokinin and ethylene.