Control of formative cell divisions in the stomatal lineage in Arabidopsis

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Plants display an enormous phenotypical plasticity and continuously form new organs during their postembryonic development. The stiff plant cell wall fixes cells within tissues, which is why the local organization and spatiotemporal control of cell division is of central importance to build the plant body. New plant organs rely on so-called formative or asymmetric divisions, i.e. the production of daughter cells with different cellular fate. Formative divisions are typically found in stem cell niches and the cell lineages originating from stem cells, e.g. during the development of stomata, the gas exchange pores on plant leaves essential for survival. Formative and asymmetric cell divisions in the stomatal lineage have been well described at a developmental level, but the underlying molecular mechanisms remain underexplored. The aim of this project is to determine how plants execute formative and asymmetric divisions and to explore how polarity, cell fate and differentiation is accomplished using the Arabidopsis stomatal lineage as a powerful system. The first part of this project addresses the question of how the core cell-cycle machinery is regulated to allow a distinct number of formative divisions and will define the role of the cell-cycle regulator CYCD7;1 that is specifically expressed during the last formative division in the stomatal lineage, and its upstream regulation. This part links the spatiotemporal regulation of the cell cycle with the process of cell differentiation to show how a formative division is initiated and, very importantly, also restricted to allow functional tissue patterning. Formative, asymmetric cell divisions require the uneven distribution of cell material to the daughter cells and the second part of the project aims at identifying proteins for the mechanisms by which plant cells generate physical asymmetries. The projects build on preliminary work and comprises multiple methodically approaches.