Out of the Niche: A Bird’s-Eye View of the Molecular Networks Controlling Root Stem Cells

The capacity of plants to generate new organs and tissues throughout their life cycle depends on the activity of the stem cells contained in meristematic tissues. Plant stem cells are organized in small, clustered populations referred to as stem cell niches. In addition to generating new undifferentiated cells, stem cell niches also provide the positional in-formation that maintains stem cell self-renewal properties and controls the non-cell-autonomous differentiation of surrounding tissues. In this review, we aim to analyze and discuss the most recent literature describing the molecular mechanism controlling the activity and the organization of the stem cell niche in the root of the model plant Arabidopsis thaliana (L.) Heynh. In particular, we will focus on the complex molecular regulatory networks that control the balance between stemness and differentiation in distal stem cells, as well as the maintenance of the mitotically inactive state of the quiescent center.