A precise coordination between cell growth, proliferation, differentiation and apoptosis is required in the development of multicellular organisms. In an ongoing screen to identify novel genes required for proper growth and patterning of the Drosophila eye, we have identified viriato (vito), the sole fruitfly homologue of the vertebrate Nol12 proteins. In this thesis we report the characterization of vito function during Drosophila development. We report that vito/Nol12 plays a crucial role in tissue growth independently of its role in cell survival. We showed that the Vito protein localizes to the nucleolus, regulating the structure and main molecular events of this subnuclear compartment in a dynamic manner. We have further shown that dMyc controls vito levels to regulate nucleolar architecture and that vito is required for dMyc to reach its full potential as a potent cell growth inducer. We further describe a targeted double RNAi screen performed in order to get a deep knowledge about the pathways working with vito during eye development. Further investigation culminated with the identification of a strong genetic interaction between vito and TGF-? signaling pathway.