Abstract

Asymmetric cell divisions provide a universal means of generating different cell fates in the development of multi-cellular organisms. However, their role in patterning growing tissues is not well understood. Asymmetric cell divisions require tight regulation of their orientation and timing. The process is particularly important in plants where growth is symplastic. In this system the orientation of divisions determines neighbourhoods of cells, and the timing determines their area. Little is known about how growth, cell division and differentiation are integrated. Formation of stomata within the Arabidopsis leaf epidermis provides a physically accessible system to study cell divisions into a developing tissue. As development is a dynamic multi-scale process, we tracked plant growth at the tissue, cell and protein level by using time-lapse microscopy. The data captured was used to produce a descriptive model of the growing and dividing cells of the leaf. Descriptive rules were then replaced by mechanistic ones in a stepwise manner, recapitulating in vivo behaviour. The resulting model of asymmetric cell divisions made testable predictions, validated by further experiments. As a result, this thesis provides a plausible model of how patterning of the stomata might be achieved by asymmetric cell divisions and how this pattern can be integrated into the developing tissue.