Quantitative analysis of the Arabidopsis shoot apical meristem during floral transition

Abstract

The stem-cell niche at the Shoot Apical Meristem (SAM) in Arabidopsis thaliana undergoes reorganisation during floral transition. This niche is maintained by a well-studied negative feedback loop between WUSCHEL and CLAVATA3, but how this network evolves during floral transition is unknown. In this study, we use confocal imaging and a custom cellular-resolution quantitative image analysis pipeline to study the expression domains of these two genes in the SAM during floral transition using transcriptional reporters of WUSCHEL and CLAVATA3 in wild-type and two mutant lines. We provide a first description of their patterning during the floral transition. We find a transient expansion in the expression domain of WUSCHEL - pointing to a role of the rib zone of the meristem in maintaining stem-cell homeostasis. Our work helps further the current understanding of stem-cell homeostasis in the shoot apical meristem, and of the organisation of the SAM in general. It provides a quantitative framework for future experimental and modelling studies of the system.