Physiological and molecular response of soybean to combined drought and heat stresses during flowering

Compared with our previous single-stress experiments, combined drought and heat (DH) triggered a synergistic photosynthetic decline and an amplified ROS burst relative to individual D or H treatments, while stomatal conductance remained D-like. Transcriptome-wide analysis revealed DH-specific down-regulation of photosystem genes, concurrent up-regulation of antioxidant enzymes and HSPs, and enrichment of 20 hub DEGs within the key co-expression module. More than half of these loci remain functionally uncharacterised in soybean; their DH-responsive expression patterns offer untapped entry points for elucidating upstream sensing, post-transcriptional regulation and metabolic rerouting under concurrent stresses. These hubs constitute immediate targets for genome editing or marker-assisted selection to uncouple growth restraint from stress defence and accelerate breeding of cultivars resilient to heat-drought events.