Dissecting auxin-minimum dependent mechanisms coordinating TZ positioning in Arabidopsis root meristem

In the Arabidopsis thaliana Root Apical Meristem (RAM), cell division and differentiation processes are finely coordinated to sustain proper root growth. These processes occur in two distinct domains, and at their boundary, the Transition Zone (TZ), cells destined to become different root tissues stop dividing and start differentiating in a coordinated manner. TZ positioning is functionally correlated with a local auxin minimum that triggers cell differentiation. However, the molecular mechanisms by which the auxin minimum instructs this transition remain unknown. To address this, we developed an inducible system to specifically alter endogenous auxin levels at the TZ. Using this system, we were able to conditionally reposition or abolish the auxin minimum. We found that shifting the minimum is sufficient to stably relocate the TZ, while its depletion leads to continuous TZ shift. Coupled with transcriptomic analysis, this approach enabled the identification of candidate genes involved in the auxin minimum response during the division-to-differentiation transition, providing new insights into the regulatory network controlling TZ positioning.