SCARECROW and SHORTROOT control the auxin/cytokinin balance necessary for embryonic stem cell niche specification.

The root apical meristem is established during embryogenesis, when its organizer, the quiescent center, is specified and the stem cell niche is positioned. The SCARECROW-SHORTROOT heterodimer is essential for quiescent center specification and maintenance. As continuous post-embryonic root growth relies upon the SCARECROW-mediated control of the cytokinin/auxin balance, we investigated the role of SCARECROW and SHORTROOT in controlling cytokinin signaling during embryonic quiescent center specification.

Acidic cell elongation drives cell differentiation in the root.

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.

Differential spatial distribution of miR165/6 determines variability in plant root anatomy.

A clear example of interspecific variation is the number of root cortical layers in plants. The genetic mechanisms underlying this variability are poorly understood, partly because of the lack of a convenient model. Here, we demonstrate that , unlike , has two cortical layers that are patterned during late embryogenesis.

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

In multicellular organisms, a stringent control of the transition between cell division and differentiation is crucial for correct tissue and organ development. In the 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.

Plant hormone cross-talk: the pivot of root growth.

Root indeterminate growth and its outstanding ability to produce new tissues continuously make this organ a highly dynamic structure able to respond promptly to external environmental stimuli. Developmental processes therefore need to be finely tuned, and hormonal cross-talk plays a pivotal role in the regulation of root growth. In contrast to what happens in animals, plant development is a post-embryonic process.

Spatial coordination between stem cell activity and cell differentiation in the root meristem.

A critical issue in development is the 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.