Auxin minimum triggers the developmental switch from cell division to cell differentiation in the Arabidopsis root

In multicellular organisms, a stringent control of the transitionbetween cell division and differentiation is crucial for correcttissue and organ development. In theArabidopsisroot, the bound-ary between dividing and differentiating cells is positioned by theantagonistic interaction of the hormones auxin and cytokinin. Cy-tokinin affects polar auxin transport, but how this impacts thepositional information required to establish this tissue boundary,is still unknown. By combining computational modeling with mo-lecular genetics, we show that boundary formation is dependenton cytokinin’s control on auxin polar transport and degradation.The regulation of both processes shapes the auxin profile in a well-defined auxin minimum. This auxin minimum positions the bound-ary between dividing and differentiating cells, acting as a triggerfor this developmental transition, thus controlling meristem size.