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

http://dx.doi.org/10.1186/S12870-025-08081-6

Chao Xia; Zhiqiang Huang; Bo Lu; Zhi Geng; Siyu Wang; Congshan Xu

Abstract

BACKGROUND(#br) Soybean (Glycine max. L, Willam 82) is an essential crop for nutrition and biodiesel, but its yield is highly vulnerable to drought and heat stress, especially during flowering. Combined stresses are more frequently encountered than individual stresses in the field, exerting more severe and distinct physiological impacts on plant growth and development. (#br)RESULTS(#br) To elucidate the underlying mechanisms, we conducted comparative physiological, biochemical, and transcriptomic analyses on reproductive stage soybeans under individual and combined drought and heat (DH) stress conditions. The results indicated significant reductions in stomatal conductance, transpiration rate, photosynthesis, and water potential under DH stress. Notably, 9441 differentially expressed genes (DEGs) were identified in response to DH stress. Many of these genes are associated with ABA metabolism, photosystem function, heat shock proteins, pentatricopeptide repeat-containing proteins, and E3-ubiquitin ligases. Weighted Gene Co-expression Network Analysis (WGCNA) clustered the unigenes into nine modules, with three key modules showing high correlation with phenotypic indices. Network analysis identified 20 hub genes within different modules as potential regulators of the soybean in response to DH stress. (#br)CONCLUSION(#br) 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.