Hormonal crosstalk at the plant–microbiome interface governing plant immunity under combined biotic and abiotic stresses

Abstract

Plant immunity is orchestrated through an intricate network of signaling pathways that enables plants to perceive, respond to, and adapt to a wide range of biotic and abiotic challenges. Increasing evidence indicates that phytohormones not only regulate immune responses but also mediate dynamic interactions between plants and their associated microbiomes, collectively shaping plant health and resilience. Rather than acting independently, hormones such as salicylic acid, jasmonic acid, ethylene, abscisic acid, auxin, cytokinins, gibberellins, brassinosteroids, strigolactones, melatonin, and peptide hormones interact through extensive crosstalk to balance growth, defense, and environmental adaptation. Beneficial microorganisms, including plant growth-promoting rhizobacteria, endophytes, mycorrhizal fungi, and biocontrol agents, further modulate these hormonal networks by producing bioactive metabolites, volatile organic compounds, and signaling molecules that enhance induced systemic resistance (ISR) and stress tolerance. This review provides a comprehensive and current knowledge on the molecular mechanisms underlying hormone-mediated regulation of plant immunity at the plant–microbiome interface. This review highlights how phytohormonal networks coordinate plant immune responses through pattern-triggered immunity, effector-triggered immunity, ISR, and systemic acquired resistance, particularly under combined biotic and abiotic stresses. It summarizes recent advances in multi-omics technologies that have improved our understanding of hormone–microbiome interactions and discusses emerging strategies such as biopriming, synthetic microbial communities, microbiome engineering, genome editing, RNA interference, nano-biopriming, artificial intelligence, and precision agriculture. Finally, the review outlines current knowledge gaps, translational challenges, and future research directions for developing sustainable, climate-resilient crop production systems and strengthening global food security.