From both a societal and an economic perspective, there is an increasing need for improved resilience in crops to biotic and abiotic stresses, which require less input of pesticides and fertilizers. Plants can deal with stresses in multiple ways, one of which is through the microbiome. Research shows that, just as in humans, a suitable microbiome is vital to plant health and functioning. It is becoming clear that plants can actively shape their microbiome. However, the mechanisms underlying this remain largely unknown. To understand the interaction between plants and their microbiome, I will explore unknown signaling relations to elucidate the mechanism by which tomato actively adjusts its microbiome under stress and how this relates to plant health and defense. To this end, I will investigate genotypic variation in, and plasticity of, microbiome recruitment by tomato. The latter I will study using phosphate deprivation, which is known to affect the root transcriptome, exudate profile, and microbiome composition. I will use time-series experiments on plant transcriptomics, root exudate metabolomics and microbiome metagenomics. I will link these datasets and predict causal relations between them. From this, candidate genes will be identified which confer the ability to recruit certain groups of organisms in the microbiome. I will validate the candidate genes using VIGS, to see their effect on microbiome recruitment.