Photosynthesis provides the primary source of energy for life by producing sugar compounds. However, photosynthetic organisms have to cope with changes in light quality and intensity to optimize their photosynthetic yield. To achieve this, they have evolved different mechanisms. When the incident light energy exceeds the absorption capacity of the photosynthetic apparatus, green photosynthetic organisms are able to dissipate the excess energy thereby preventing the production of compounds harmful for the cell. On the other hand, when incident light becomes limiting, state transitions allow optimizing the photosynthetic performance by a rearrangement of the light-harvesting antenna. This conserved process occurs through the reversible phosphorylation of light-harvesting proteins mediated by chloroplast kinases and phosphatases. During my thesis I studied the thylakoid-associated kinases Stt7/STN7 and Stl1/STN8 involved in light adaptation in Chlamydomonas reinhardtii and Arabidopsis thaliana. The biochemical characterization in alga and the physiological role of these kinases in plants have been investigated.