Chemical dialogues in the rhizosphere: Metabolomics perspectives on plant defence and microbial interactions

Plant growth-promoting rhizobacteria (PGPR) are plant-beneficial organisms in the rhizosphere that stimulate plant growth and development, boost yield, and directly or indirectly protect plants from abiotic and biotic stresses. They further prime plants for future stress attacks. Plant-microbe interactions involve chemical communication in the rhizosphere, resulting in tripartite interactions (plants-beneficial microbes-pathogenic microbes), although beneficial microbes like PGPR are not always present in this environment. However, there is little detailed information about these communications, i.e., the tripartite interactions and their effects on the plant's chemical makeup (metabolome). Understanding how PGPR influences plant resistance and priming at the metabolic and molecular levels is still incomplete, and ongoing research is focused on decoding rhizosphere communication and exploring chemical interactions within this vital ecosystem. This review synthesises the most recent advancements in metabolomics techniques with a particular emphasis on bipartite and tripartite interactions, the intricate chemical dialogues among plants, beneficial microbes, and pathogens. It offers a comprehensive and integrated perspective, demonstrating how cutting-edge metabolomics approaches uncover novel molecular mechanisms that shape plant defence strategies at a systems level. Furthermore, it explores the chemical communication in the rhizosphere that aids plants in defending against environmental stresses, focusing on the significant role of metabolomics in unravelling these complex interactions. Metabolomics represents a powerful tool for dissecting the intricate chemical networks in the rhizosphere, offering new insights into the molecular basis of plant resistance and priming mediated by PGPR. Advancing this knowledge will facilitate the development of sustainable agricultural practices by harnessing beneficial plant-microbe interactions to improve crop resilience and productivity.