Physiological and molecular functions of ABC1K1 kinase during early development of Arabidopsis thaliana.

Photosynthesis is the key bioenergetic mechanism for photosynthetic organisms. This process takes place entirely within the chloroplast, a specialized organelle present in cells of plants and eukaryotic algae. The chloroplast contains a system of internal thylakoid membranes in which the components of the photosynthetic machinery are inserted . Furthermore, these membranes, mainly composed of glycerolipids and prenyllipids, are fused to lipid droplets called plastoglobules which have been shown to play an important role in plastids biogenesis, stress response, senescence and prenylquinones metabolism. These lipid droplets contain many prenylquinones as well as carotenoids and phytylesters, and possess a specific set of associated proteins. Among the plastoglobular proteins, the most abundant are structural proteins called Fibrillin, and the members of the Activity of BC1 complex Kinase (ABC1K) family. Many studies suggest that at least some of these plastoglobular kinases, such as ABC1K1 and ABC1K3, play a role in red-light mediated development as well as in chloroplast functions, especially in photosynthesis regulation and chloroplast metabolism, but their phosphorylation targets and the signaling pathway(s) are still unknown. Moreover, the role of ABC1K1 was mostly investigated on adult plants, while little is known about its role in young seedling.

The aim of this thesis is to investigate the role of ABC1K1 in physiological and molecular functions during the early development of Arabidopsis thaliana, particularly under red light when the role of this kinase appears to be even more relevant. This will allow to better understand the molecular mechanisms regulating chloroplast development and its functions.