In multicellular organisms, a stringent control of the transition between cell division and differentiation is crucial for correct tissue and organ development. In the Arabidopsis root, the boundary between dividing and differentiating cells is positioned by the antagonistic interaction of the hormones auxin and cytokinin. Cytokinin affects polar auxin transport, but how this impacts the positional information required to establish this tissue boundary, is still unknown. By combining computational modeling with molecular genetics, we show that boundary formation is dependent on cytokinin's control on auxin polar transport and degradation. The regulation of both processes shapes the auxin profile in a welldefined auxin minimum. This auxin minimum positions the boundary between dividing and differentiating cells, acting as a trigger for this developmental transition, thus controlling meristem size.plant hormones | cell differentiation | root meristem | computational modeling

SUMMARY A critical issue in development is 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 centre 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 leave the meristem, thus controlling the rate of differentiation. In this way, SCR simultaneously controls stem cell division and differentiation ensuring coherent root growth.

Highlights d Upon germination, cell divisions generate a PLT drop that forms the transition zone d A PLTs-ARR12 mutual antagonism restricts early root meristem expansion d ARR1 repression of cell division via KRP2 is key for meristem size stabilization

Highlights d Cytokinin acts in the LRC to coordinate cell differentiation of the root meristem d Cytokinin controls auxin levels via PIN5 and GH3.17 to trigger cell differentiation d PIN5 and GH3.17 control auxin levels specifically in the LRC d LRC serves as an auxin sink which controls meristem size thus organ growth

After renal transplantation, health benefits of proper metabolic balance that include reduced body fat, weight loss, lower cholesterol and triglycerides levels and an improvement, fasting glucose levels can be obtained when dietary intervention occurred.