Selenium Alleviates Manganese Toxicity in ‘Red Fuji’ Apple: Insights From Combined Physiological and Transcriptomic Approaches

Selenium (Se), a beneficial element, plays a pivotal role in mitigating plant stress, yet its potential in alleviating manganese (Mn) toxicity in apple trees remains poorly understood. This study explores the potential of Se in alleviating Mn-induced stress in Malus domestica Borkh. cv. Red Fuji, a cultivar known for its sensitivity to Mn. Through a combination of physiological analysis and transcriptomic profiling, we provide comprehensive insights into the mechanisms by which Se enhances Mn tolerance. The results demonstrated that selenite application balanced nutrient elements, stabilized the photosynthetic system, and reduced oxidative stress. Additionally, selenite promoted cell wall remodeling and modulated hormone levels. Transcriptome analysis further revealed that selenite regulated genes associated with polyunsaturated fatty acid hydrolase, sucrose hydrolase, and photosynthesis, indicating its role in alleviating Mn stress. GO and KEGG enrichment analyses highlighted that differentially expressed genes were enriched in pathways related to phenylpropanoid biosynthesis, alpha-linolenic acid metabolism, and galactose metabolism, suggesting key metabolic pathways involved in Mn stress responses. Weighted gene co-expression network analysis (WGCNA) identified core module genes strongly correlated with antioxidant enzymes and substances, chlorophyll content, and mineral element concentrations. In conclusion, Se effectively mitigates Mn stress in 'Fuji' apples through multi-level regulatory mechanisms, providing a theoretical foundation for the application of Se-enriched agriculture in apple cultivation.