The rice weevil, Sitophilus oryzae, is a worldwide pest insect, for which grains serve as a source of food for adults and a habitat for larval development. S. oryzae has evolved an intracellular symbiotic interaction (endosymbiosis) with a bacteria, Sodalis pierantonius, which transform the carbohydrates from the grains to critical amino acids for its host. This interaction enables young adult weevils to strengthen their cuticle before emerging from the grain. The bacteria is present in specific cells within the weevil: the bacteriocytes, which are organised into an organ, the bacteriome. During the weevil development, the unique bacteriome present next to the larval gut is reshaped into multiple bacteriomes localised along the adult midgut. While the bacterial load is stable in larvae, it increases in young adults, coinciding with the cuticle synthesis, and bacteria are then eliminated once the cuticle is finished. However, how the bacterial load is controlled by young adult weevils is still unknown. Recent work using transcriptomics at different stages of development in S. oryzae showed that some genes from the Hippo signalling pathway are more expressed in young adult weevils in interaction with S. pierantonius, than in adults not containing this bacteria (aposymbiotic individuals). A signaling pathway is a succession of chemical reactions, enabling the cell to detect and respond to a signal, for example, nervous or hormonal. The Hippo signalling pathway has been mostly studied in mammals and drosophila, where it was found to be involved, amongst others, in cell fate (e.g. proliferation, growth and death). The main objective of this project is to use functional genomics to investigate whether the Hippo signalling pathway is involved in the regulation of bacterial load in young adult weevils. Understanding the mechanisms involved in the interaction between S. oryzae and S. pierantonius can help find new ways of control against cereal weevils.