Transcriptome Analysis of the Regulatory Mechanism of Exogenous Manganese Sulfate Application on Wheat Grain Yield and Carotenoids

Given the critical role of manganese (Mn) as an essential micronutrient in wheat growth and development and the high efficiency of foliar fertilization in optimizing nutrient uptake and improving crop quality, this study aimed to elucidate the regulatory effects of exogenous manganese sulfate application on wheat grain yield and carotenoid accumulation. Methods: Field experiments were conducted from 2022 to 2024 at the Shuitou Experimental Station of the Cotton Research Institute, Shanxi Agricultural University (35°11′ N, 111°05′ E), using the wheat cultivar ‘Jinmai 110’. Foliar applications of manganese sulfate were administered at concentrations of 0.5 g/kg, 1.0 g/kg, and 1.5 g/kg, with water serving as the control (CTRL). Spraying was conducted on the upper canopy during the flowering and grain-filling stages, applied every 7 days for a total of three times. Samples for transcriptomic analysis were collected within 24 h of the final application. At maturity, yield-related traits and grain carotenoid contents were assessed. Results: Foliar application of 1.0 g/kg MnSO4 significantly enhanced both grain yield and carotenoid content in wheat. Transcriptome sequencing revealed that treatment with 1.0 g/kg manganese sulfate (M2) resulted in 4761 differentially expressed genes (DEGs), including 2933 upregulated and 1828 downregulated genes, relative to CTRL. Gene Ontology (GO) analysis showed that in the M2 vs. CTRL comparison, 819 GO terms were significantly enriched among upregulated DEGs and 630 among downregulated DEGs. Specifically, upregulated genes were associated with 427 biological process terms and 299 cellular component terms, while downregulated genes were linked to 361 biological processes and 211 cellular components. Enriched functions primarily included cellular processes, metabolic processes, catalytic activity, and binding. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed 809 annotations for upregulated DEGs and 330 for downregulated DEGs, mainly related to photosynthesis, carotenoid biosynthesis, phenylpropanoid biosynthesis, and plant hormone signal transduction. In total, 43,395 alternative splicing (AS) events were identified from 17,165 genes, including 445 upregulated and 319 downregulated AS events, primarily enriched in photosynthesis and plant hormone-related pathways. Conclusion: Foliar application of manganese sulfate significantly modulates gene expression in wheat grains, thereby improving both yield and carotenoid accumulation. Key biological processes affected include photosynthesis, plant hormone signal transduction, and the carotenoid biosynthetic pathway. The interactions among these regulatory networks constitute a complex molecular mechanism through which exogenous Mn influences agronomic traits. These findings provide mechanistic insights and practical implications for enhancing wheat productivity and nutritional quality through foliar manganese application.