Cultivar-specific responses to organic selenium treatment in tea plants: insights into selenium metabolism and...

Foliar application of organic selenium (Se) is a safe and efficient approach to produce Se-enriched tea. Nevertheless, the regulatory mechanisms of organic Se underlying tea plant growth and tea quality remain poorly understood. This study explored the impacts of organic Se on Se accumulation, photosynthetic parameters, metabolite contents, and transcriptome profiles in different tea plant cultivars. Exogenous organic Se markedly elevated leaf Se levels in 'Zhenong 117' and 'Chunyu 1'. Combined transcriptome and metabolome analysis demonstrated that ABC transporters mediated organic Se uptake and accumulation. Key genes (CGS, CTH) in Se metabolism displayed distinct cultivar-specific expression, driving differential Se metabolic processes. Organic Se improved tea quality by boosting total and umami-related amino acid contents, lowering the polyphenol-to-amino acid ratio, and promoting soluble sugar accumulation via regulating amino acid and sugar metabolic pathways. The two cultivars adopted divergent adaptive strategies, 'Zhenong 117' enhanced Se tolerance through activated glutathione metabolism, while 'Chunyu 1' adapted by modulating auxin, ethylene, brassinosteroid and jasmonic acid signaling pathways. Overall, cultivar-specific molecular responses determined the differential Se enrichment and quality formation in tea plants under organic Se treatment.