Spatial Coordination between Stem Cell Activity and Cell Differentiation in the Root Meristem

• SCR directly suppresses ARR1 in the quiescent center, allowing stem cell division
• Suppression of ARR1 in the quiescent center titrates auxin production
• Via auxin, SCR exerts a long-distance control on ARR1 in the transition zone
• SCR coordinates stem cell activity with cell differentiation at the transition zone

SummaryA critical issue in development is the coordination of the activity of stem cell niches with differentiation of their progeny to ensure coherent organ growth. In the plant root, these processes take place at opposite ends of the meristem and must be coordinated with each other at a distance. Here, we show that in Arabidopsis, the gene SCR presides over this spatial coordination. In the organizing center of the root stem cell niche, SCR directly represses the expression of the cytokinin-response transcription factor ARR1, which promotes cell differentiation, controlling auxin production via the ASB1 gene and sustaining stem cell activity. This allows SCR to regulate, via auxin, the level of ARR1 expression in the transition zone where the stem cell progeny leaves the meristem, thus controlling the rate of differentiation. In this way, SCR simultaneously controls stem cell division and differentiation, ensuring coherent root growth.

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