Combined transcriptomics and metabolomics analysis reveals the molecular responses of heat tolerance during germination stage in sesame.

Sesame is an important oilseed crop, but its germination stage growth is increasingly limited by heat stress under climate warming. However, the molecular responses underlying heat tolerance in sesame germination stage remain unclear. In this study, a heat-tolerant genotype (G14) and a heat-sensitive genotype (G9) were compared under different durations of high-temperature treatment using phenotypic, metabolomic, and transcriptomic analyses. The results showed that G14 maintained better growth than G9 under both normal and heat stress conditions, with a more pronounced advantage under high temperature. G14 also accumulated lower levels of hydrogen peroxide (H2O2) under heat stress, suggesting reduced oxidative damage and enhanced heat tolerance. Metabolomic analysis showed that differentially accumulated metabolites (DAMs) in G14 were mainly enriched in lipid metabolism, antioxidant systems, and secondary metabolism, which were activated at early stages and maintained throughout heat stress. In contrast, DAMs in G9 were primarily associated with hormone signaling, carbon metabolism, energy metabolism, and vitamin metabolism. Transcriptomic analysis further showed that heat stress induced extensive changes in gene expression. KEGG enrichment analysis suggested that differentially expressed genes (DEGs) in G14 were mainly involved in maintaining key physiological processes, including photosynthesis, protein processing, and lipid metabolism, whereas those in G9 were predominantly associated with defense and signaling pathways. Integrated metabolomic and transcriptomic analyses supported these patterns and indicated a close coordination between gene expression and metabolic changes. Transcription factor analysis identified members of the ERF and bHLH families as candidate transcription factors associated with the heat stress response in sesame. These findings provide new insights into the molecular responses underlying heat tolerance during sesame germination.