Active Galactic Nuclei may play a major role in the transition from gas-rich, star-forming galaxies, to red gas-deprived passive galaxies. Theoretical models predict that AGN may be able to perturb or remove the gas from galaxies via powerful winds, thus quenching star-formation. Today’s flagship Instruments - like ALMA and MUSE/VLT - allow both to routinely detect and spatially resolve AGN-driven massive winds, and to measure the properties of the host galaxies, to derive scaling relations. One of the most important scaling relations for star-forming galaxies is the one involving the gas fraction, which is a useful tool also to assess the net effect of the AGN on the host galaxy inter stellar medium. I will review the main observational and theoretical results in this field, and discuss recent results based on large AGN samples.