In the Arabidopsis thaliana root, stem cells divide in the apical stem cell niche of the meristem and originate daughter cells that divide until they reach a distal boundary denominated transition zone where they start differentiating. At the end of root meristem development, a balance between cell division and cell differentiation is reached to maintain indeterminate root growth. The transition zone is early established during meristem development due to a drop of PLETHORA 2 gene levels in the distal part of the meristem. At later stage of root development, once the transition zone is established, an auxin minimum sets the position of this boundary, determining the size of the meristem and the rate of root growth. Nevertheless, how the PLETHORA 2 drop acts to establish the transition zone first and how the auxin minimum acts to stabilize the transition zone at later stage of root development is still unknown. Aim of this project is to unveil these molecular mechanisms by using both a molecular and a genetic approach.
The results foreseen in this proposal will shed light on the molecular mechanisms through which the circuit PLT2/auxin determines and sets the TZ. The results of this research will have an impact well beyond the organ being studied, as developmental boundaries analogous to the TZ are present in all plant organs. In addition, the establishment and maintenance of developmental boundaries is crucial also in animal development: apart from the differences in growth factors and other molecular components specifically acting in plants and animals, these results may shed light on general principles of this control common to the two kingdoms. To understand basic principles, fundamental strategies of development in plants and animals should in fact be compared.
On the other hand, plants are essential for the sustainability of our ecosystems: in the next decades it will become essential to understand plant development in detail and to learn how plants cope with a changing environment. Moreover, roots critically influence nutrient and water uptake efficiency, and consequently the overall performance of (crop) plants. Gaining knowledge and control of the regulatory circuits controlling root growth and development and understanding how they are involved in adapting root growth in response to the environment is therefore not only a most intriguing scientific challenge but is also of the utmost importance for crop breeding and agricultural practices.
Furthermore, activities of selected genes will be integrated into a recently developed root computational model (1), which incorporates cellular and tissue growth dynamics arising from the combined activities of individual cell¿s genes networks and generates, as emergent properties, all the root zones and boundaries (1). The integrated model will provide further hypotheses that can be tested and will allow us to unravel the complexity behind the establishment and maintaining of the TZ and root growth.
Bibliography
1. Salvi E., Rutten J., Di Mambro R, Polverari L., Licursi V., Negri R., Dello Ioio R., Ten Tusscher K., Sabatini S. A self-organized PLT/AUXIN/ARR-B network controls the dynamics of root zonation development in Arabidopsis thaliana. Develop. Cell 2020, 53 (4): 431-443. doi.org/10.1016/j.devcel.2020.04.004