Time-Dependent Physiological and Transcriptomic Adaptations of Sorghum to Drought Stress
Sorghum responds to drought through a coordinated, time-dependent shift from early physiological stress and metabolic suppression to later activation of antioxidant defenses, hormone signaling, and carbohydrate remobilization pathways that enhance survival under prolonged water deficit.
Keywords: Drought stress, Gene expression, Phytohormones, Regulatory network, Sorghum, Transcriptome
Drought stress disrupts sorghum physiology by impairing water uptake , photosynthesis, and cellular homeostasis. Relative water content (RWC) declined rapidly within 24 h of stress, reflecting acute dehydration, but partially recovered under prolonged exposure due to adaptive mechanisms such as stomatal closure, reduced transpiration, and osmotic adjustment. However, sustained stress ultimately led to system collapse, where water uptake could no longer compensate for loss. Concurrently, chlorophyll content decreased progressively, indicating impaired photosynthetic capacity likely driven by chloroplast damage and oxidative stress. Proline (PRO) accumulation increased significantly, contributing to osmotic balance and protection against peroxidative damage. Elevated malondialdehyde (MDA) levels at 48 h signaled peak lipid peroxidation, after which enhanced antioxidant enzyme activities (SOD and POD) and PRO accumulation mitigated oxidative damage. This suggests a temporal shift from injury to active defense, with ~48 h representing a critical transition point in drought response.
Transcriptomic analyses further revealed dynamic, time-dependent regulatory strategies. Early drought stress suppressed gene expression to conserve energy, whereas prolonged stress (≥120 h) activated compensatory and recovery pathways, including NAC transcription factors. Functional enrichment highlighted shifts from photosynthetic regulation to membrane stability, ion binding, and amino acid metabolism after 48 h. Hormone signaling pathways, including abscisic acid (ABA), auxin, cytokinin, and jasmonic acid, were extensively reprogrammed, modulating stomatal closure, growth, and stress signaling. Notably, ABA-related genes (e.g., PP2C) were upregulated to enhance drought tolerance. Carbohydrate metabolism emerged as a central adaptive mechanism, with differential expression of genes involved in starch, sucrose, and cellulose degradation, indicating a shift toward energy remobilization and survival at the expense of growth. Weighted gene co-expression network analysis identified key hub genes and 140 hormone-related and 107 carbohydrate metabolism-related differentially expressed genes as candidates for improving drought tolerance. Collectively, these findings highlight a coordinated physiological and molecular transition from short-term stress responses to long-term adaptation, providing targets for future sorghum breeding efforts.
SorghumBase Examples:
Ma Q, Wang R, He F, Wan W, Liu X, Zhang J, Li K, Ren M. Response of sorghum (Sorghum bicolor (L.) Moench) to various-duration of drought: physiology, transcriptome, and weighted gene co-expression network analysis. BMC Plant Biol. 2026 Feb 10;26(1):488. PMID: 41663957. doi: 10.1186/s12870-026-08297-0. Read more
