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

• The combination of elevated temperature and drought reduces wheat plant height by 18 % and TGW by 27 .% • Elevated CO 2 increases spike number by 42 % and husk weight six-fold. • Elevated CO 2 and drought raise water-use efficiency by 320 % while reducing transpiration by 65 %. • Drought induced the smallest transcriptomic changes: only 826 up- and 425 downregulated genes. • Potential marker genes PM19L, GSTF1, PIP2–6 highlight targets for multifactorial stress breeding. Climate change intensifies environmental stressors such as drought and heat, posing a significant threat to crop productivity, while elevated CO 2 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 CO 2 (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.