The primary research interest of the Plant Hormone Biology group is the role of plant hormones and other signaling molecules in the communication of plants with beneficial and harmful organisms, mostly belowground. For example, we study the exudation by plants of strigolactones into the rhizosphere to signal host presence to symbiotic arbuscular mycorrhizal fungi and the abuse of this signaling relation by parasitic plants that use the same molecules for host detection. The fact that the strigolactones also have an endogenous signaling function as plant hormones, regulating root and shoot architecture makes this interaction even more intriguing. The intricate signaling role of the strigolactones has prompted us to also research other rhizosphere signaling relationships such as the induction of cyst nematode hatching by root exudates and the recruitment of the root microbiome by plants. Important aspects of our work on communication are the use of different approaches, including the use of omics technologies, to unravel how these signaling molecules are biosynthesised and perceived, how their production is regulated, and how important they are for the interaction. To be able to do such studies we use a broad range of expertise, ranging from analytical chemistry, including metabolomics, for detection of the signaling molecules, RNAseq and data integration, through molecular biology and biochemistry for the isolation of key genes to metabolic engineering to change signaling molecule production and bioassays to study the consequences of the altered signaling molecule production for the interaction.