Comparative Investigation into Metabolic Pathways and Corresponding Gene Expression Profiles of Sorghum Under Drought Stress

Drought stress is one of the most critical abiotic stresses restricting global crop production, and sorghum plays an important role in arid and semi-arid areas due to its inherent drought tolerance compared to many other cereals. However, significant variation in drought tolerance exists among different sorghum genotypes, which provides an opportunity to dissect the underlying mechanisms. In this study, a drought-tolerant sorghum line (LNR-6) and a drought-sensitive line (LR-2381) were used for comparative analysis. Plants were grown under two water regimes: well-watered conditions (CK, soil water content maintained at 40%) and drought stress (soil water content reduced to 24%). Integrated transcriptomic and non-targeted metabolomic analyses were conducted to investigate the physiological and molecular mechanisms underlying sorghum drought tolerance. Phenotypic analysis showed that drought stress significantly reduced plant height and chlorophyll content in the drought-sensitive genotype, whereas the drought-tolerant genotype showed only minor changes. Transcriptome analysis identified several enriched functional categories of differentially expressed genes between the two genotypes under drought stress. Among them, genes associated with limonene and pinene degradation, photosynthesis, and photosynthesis-antenna proteins were significantly enriched and may be involved in drought-response regulation. Metabolomic analysis revealed significant accumulation of flavonoids and phenylpropanoids under drought conditions. KEGG pathway enrichment further indicated that flavone and flavonol biosynthesis, flavonoid biosynthesis, and phenylpropanoid biosynthesis were the most significantly enriched metabolic pathways. Overall, these findings enhance our understanding of the coordinated transcriptional and metabolic responses underlying drought tolerance in sorghum.