Diatoms are unicellular microalgae found in many aquatic areas (oceans, intertidal zones, freshwater bodies, soils, ice zones) and are responsible for about 20% of oxygen production on earth. These photosynthetic eukaryotes are the result of a secondary endosymbiosis between a heterotrophic protist and a microalga, itself the result of a primary endosymbiosis between a heterotrophic protist and a cyanobacterium (Archaeplastida). Thus, it is expected that in diatoms, the transport of nuclear-encoded proteins from the cytosol to the chloroplast and the coordination of intracellular genome expression have different characteristics than in Archaeplastida. Diatoms are therefore particularly interesting from an evolutionary point of view to study the dynamics of intracellular genomes, the modalities of protein translocation in the chloroplast and the genetic determinants of photosynthetic adaptation to different aquatic life modes