High-resolution gene expression datasets of ontogenetic zones in the root apical meristem

In plants, apical meristems allow continuous growth along the body axis. Within the root apical meristem (RAM), a group of slowly dividing quiescent center (QC) cells is thought to limit stem cell activity to directly neighboring cells (Cowels, 1956; van den Berg et al., 1997), thus endowing them with unique properties, distinct from displaced daughters. This binary identity of the stem cells stands in apparent contradiction with the more gradual changes in cell division potential (Bennett and Scheres, 2010) and differentiation (Yamaguchi et al., 2008; 2010; Furuta et al, 2014; Geldner, 2013; Masucci et al., 1996; Dolan and Costa, 2001) that occur as cells move further away from the QC. To address this paradox and to infer molecular organization of the root meristem, we used a whole-genome approach to determine dominant transcriptional patterns along root ontogeny zones. We found that the prevalent patterns are expressed in two opposing gradients. One is characterized by genes associated with development, the other enriched in differentiation genes. We confirmed these transcript gradients, and demonstrate that these translate to gradients in protein accumulation and gradual changes in cellular properties. We also show that gradients are genetically controlled through multiple pathways. Based on these findings, we propose that cells in the Arabidopsis root meristem gradually transition from ‘stemness’ towards differentiation.