Integrated transcriptomic, metabolomic, and physiological analyses underlying differential responses to potassium deficiency in sesame

Potassium (K) is an essential macronutrient for plant growth and stress resistance, and K deficiency severely limits sesame (Sesamum indicum L.) yield and oil quality. Despite substantial genotypic variation in K tolerance among sesame cultivars, the molecular mechanisms underlying this variation remain poorly characterized. Here, an integrated physiological, transcriptomic, and metabolomic analysis was performed on two contrasting sesame cultivars (K sensitive ZZ9 and K tolerant WZM6) grown under low K (LK, 0.2 mmol L− 1) and adequate K (CK, 2 mmol L− 1) conditions to identify key traits and genes associated with K tolerance. Physiological analysis showed that low K stress inhibited plant growth, reduced leaf K content, and altered photosynthetic and sucrose metabolism-related enzyme activities in both cultivars. WZM6 maintained better performance with 34.3% less reduction in plant height, 29.5% less loss in leaf K content, and 12.8% reduction in Rubisco activity. Transcriptomic profiling identified 513 and 195 unique differentially expressed genes (DEGs) in ZZ9-LK vs. ZZ9-CK and WZM6-LK vs. WZM6-CK, respectively. GO and KEGG enrichment analyses revealed that DEGs in ZZ9 were enriched in protein metabolic processes and mRNA surveillance pathway, while WZM6 DEGs were associated with small molecule metabolism, intracellular transport, and carbon/amino acid metabolism. Key K transporter genes (HAK5, POT5, POT6) and nitrate transporters (NRT2.1) were more highly upregulated in WZM6, contributing to its superior K uptake capacity. Metabolomic analysis detected 294 differentially accumulated metabolites (DAMs), with 102 and 96 cultivar specific DAMs in ZZ9 and WZM6, which were enriched in plant secondary metabolite biosynthesis, ABC transports and biosynthesis of amino acids. Integrated transcriptomic-metabolomic analysis highlighted glutamate biosynthesis (GS/GOGAT pathway) and sucrose metabolism as core regulatory networks, with WZM6 maintaining stable glutamine accumulation and sucrose synthase activity under low K stress. Therefore, WZM6 achieves K tolerance through enhanced K uptake via transporters, targeted transcriptional regulation, and metabolic remodeling of carbon-nitrogen metabolism. Our findings provide valuable genetic resources and candidate genes for breeding K efficient varieties, which is essential for improving yield stability and reducing K fertilizer inputs in K deficient fields.