High Light and High Temperature Reduce Photosynthesis via Different Mechanisms in the C₄ModelSetaria viridis

AbstractC4plants frequently experience damaging high light (HL) and high temperature (HT) conditions in native environments, which reduce growth and yield. However, the mechanisms underlying these stress responses in C4plants have been under-explored, especially the coordination between mesophyll (M) and bundle sheath (BS) cells. We investigated how the C4model plantSetaria viridisresponded to a four-hour HL or HT treatment at the photosynthetic, transcriptomic, and ultrastructural levels. Although we observed a comparable reduction of photosynthetic efficiency in HL- or HT-treated leaves, detailed analysis of multi-level responses revealed important differences in key pathways and M/BS specificity responding to HL and HT. We provide a systematic analysis of HL and HT responses inS. viridis, reveal different acclimation strategies to these two stresses in C4plants, discover unique light/temperature responses in C4plants in comparison to C3plants, and identify potential targets to improve abiotic stress tolerance in C4crops.