All roads lead to dome: Multicellular dynamics during de novo meristem establishment in shoot regeneration.

Shoot apical meristems (SAMs) harbor persistent stem cells and give rise to above-ground organs throughout life. In tissue culture-based shoot regeneration, a subpopulation of pluripotent callus cells is specified into SAMs. How callus cells decide whether or not to become SAMs stands as an important question in developmental biology. Furthermore, the developmental basis underlying the de novo construction of dome-shaped SAMs remained largely unknown. Recent high-resolution analyses have revealed the spatiotemporal dynamics of cell fate determination and meristem establishment during shoot regeneration. Cell fates to become meristem are actively determined through interactions between neighboring cells, rather than by cell-autonomous fate transition. Inter-cell layer communication via mobile signal or mechanical cue may enable meristem construction. By integrating recent insights from the two-step tissue culture system in Arabidopsis together with other shoot regeneration systems, we depict the process of de novo meristem establishment as a dynamic multicellular system.