The Emerging Role of Phytohormone Crosstalk in Orchestrating Plant Stress Tolerance

To integrate many environmental inputs into precisely calibrated physiological responses, plants rely on a highly interconnected hormonal network. Recent mechanistic evidence shows that these signalling modules function as an integrated system shaped by extensive crosstalk, even though individual phytohormones like abscisic acid, auxin, jasmonates, salicylic acid, cytokinins, ethylene, gibberellins, and brassinosteroids have historically been studied as distinct pathways. Starting with shared sensing mechanisms, secondary messengers, transcriptional regulators, and biosynthetic interdependencies that provide recurring integration nodes, this review summarises current knowledge of phytohormone crosstalk from a network-centric perspective. In addition to mediating context-dependent immune outputs against biotrophic, necrotrophic, and viral pathogens, we investigate how these molecular intersections coordinate plant responses to drought, salinity, severe temperatures, and flooding. The dynamic rewiring of SA–JA–ET immunological networks, ABA-centred abiotic stress responses, and growth–stress trade-offs, mediated by GA, BR, and DELLA hubs, is also highlighted. The paper also emphasises how infections depress host immunity by exploiting hormonal interplay. Lastly, we go over translational approaches to creating climate-resilient crops via precision nanodelivery of hormone modulators, programmable synthetic circuits, and CRISPR-mediated mutation of signalling hubs. This synthesis presents a cohesive framework for understanding how phytohormone crosstalk determines plant stress resilience and how manipulating it offers new prospects for crop improvement, integrating multi-omics evidence and recent mechanistic discoveries.