Ricerc@Sapienza

Plant developmental plasticity relies on the activities of meristems, regions where stem cells continuously produce new cells [1]. The lateral root cap (LRC) is the outermost tissue of the root meristem [1], and it is known to play an important role during root development [2-6]. In particular, it has been shown that mechanical or genetic ablation of LRC cells affect meristem size [7, 8]; however, the molecular mechanisms involved are unknown.

In multicellular systems, the control of cell size is fundamental in regulating the development and growth of the different organs and of the whole organism. In most systems, major changes in cell size can be observed during differentiation processes where cells change their volume to adapt their shape to their final function. How relevant changes in cell volume are in driving the differentiation program is a long-standing fundamental question in developmental biology.

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.