Plants are subjected to diverse biotic and abiotic stresses in life. These can induce changes in transcriptomics and metabolomics, resulting in changes to root and leaf exudates and, in turn, altering the plant-associated microbial community. Emerging evidence demonstrates that changes, especially the increased abundance of commensal microbes following stresses, can be beneficial for plant survival and act as a legacy, enhancing offspring fitness. However, outstanding questions remain regarding the microbial role in plant defense, many of which may now be answered utilizing a novel synthetic community approach. In this article, building on our current understanding on stress-induced changes in plant microbiomes, we propose a 'DefenseBiome' concept that informs the design and construction of beneficial microbial synthetic communities for improving fundamental understanding of plant-microbial interactions and the development of plant probiotics.