Integrative morpho-physiological and transcriptomic insights into wheat responses to combined drought, heat, and elevated CO₂ under future climate conditions

Climate change intensifies environmental stressors such as drought and heat, posing a significant threat to crop productivity, while elevated CO2 concentrations generally have a positive effect on photosynthetic performance and, under certain conditions, can compensate for the negative effects of stress factors. We investigated the morpho-physiological and transcriptional responses of bread wheat (Triticum aestivum L.) to drought (D), elevated temperature (eT), and elevated CO2 (eC) applied individually, in pairs (eT+D, eC+D, eC+eT), and as a triple combination (eC+eT+D). The eT+D combination resulted in the most severe reductions in growth and yield, whereas eC consistently enhanced water-use efficiency. Transcriptome profiling revealed extensive reprogramming of gene expression under multifactorial treatment, including enrichment of hormone signalling and photosynthesis pathways. Key transcription factor families (e.g., MYB, NAC, WRKY) and potential marker genes were differentially regulated across treatments. Co-expression network analysis identified gene modules associated with critical traits, such as shoot biomass and grain yield, emphasising roles for stress-responsive signalling. These findings advance our understanding of wheat adaptation to climate-related stress combinations and provide molecular targets for breeding climate-resilient cultivars.