Integrated Multi-Omic Analyses Uncover a Regulatory Link Between Photosynthesis and Drought Tolerance in Field-Grown Sorghum.

Global warming and increasing water scarcity pose major challenges to agriculture, emphasising the need to translate stress-biology insights into the development of drought-resilient cultivars. In this study, we evaluated a panel of six diverse sorghum (Sorghum bicolour) accessions grown under field-imposed drought conditions in central Arizona, integrating physiological, transcriptomic and oxidative stress measurements over a 7-week period. Using network analyses informed by co-expression correlations, transcription factor (TF) binding motif signatures and protein-protein interactions, we identified a drought-associated module strongly correlated with photosynthetic capacity. This module contained a stress-responsive TF, SbDof8 (referred to here as SbCDF2/3-like, or SbCDF2/3L), as a highly connected hub gene, and CDF2/3-associated binding motifs were over-represented in the promoters of co-expressed module members. These co-expressed members were enriched for stress response, metabolic and photosynthesis-related processes, and consistently maintain higher expression under drought in tolerant compared to sensitive accessions. Analysis of an independent sorghum drought time-course dataset comprised of two unique accessions revealed concordant expression patterns of SbCDF2/3L and photosynthesis-associated module genes between drought-tolerant and drought-sensitive genotypes, reinforcing the robustness of this regulatory module. Together, our results highlight a subset of photosystem I (PSI)-related genes, including light-harvesting proteins, PSI subunits and importantly, a potential drought-responsive transcriptional regulator that are collectively upregulated in resilient accessions as a means of coping with drought response. These data highlight promising breeding targets for improving drought resilience and biomass productivity in sorghum under field conditions.