The aim of our research line at the EEZ-CSIC (plant-beneficial microorganisms communication in the rhizosphere) is to gain knowledge on the biosynthesis and regulation of plant signalling molecules (mainly strigolactones and other apocarotenoids, but also other molecules such as flavonoids), which are key for the establishment of symbiosis with beneficial microorganisms present in the rhizosphere. We intend to understand how the production of these molecules, and therefore the establishment of symbiosis, is regulated by different environmental stresses, using we use plant crops with high agronomical and economical interest in Spain and Europe as tomato, lettuce and pea. The final goal is to pave the way for the development of new alternative strategies to use beneficial microbes as biofertilizers and bioprotection agents (against biotic and abiotic stresses) in the context of sustainable agriculture. Interestingly, strigolactones, in addition to signalling molecules, are plant hormones regulating several different processes in plants, such as above- and below-ground plant architecture, adventitious root formation, secondary growth, reproductive development, leaf senescence and defence responses. Therefore, the knowledge on the regulation of the biosynthesis of these metabolites will also provide the basis for future biotechnological applications in order modulate plant physiology.