Physiological insights into the responses of tea plants to aluminum through an integrated transcriptomic and metabolomic analysis

Abstract Tea plants ( Camellia sinensis ) demonstrate significant tolerance to aluminum (Al) and even require it for optimal growth. However, the mechanisms involved remain poorly understood. This study explored the responses of tea plants to varying Al concentrations at both metabolomic and transcriptomic levels. Compared to 0 mM Al treatment, low Al concentrations (0.4 mM) enhanced root vitality by 8.91%, while higher Al concentrations (10 and 100 mM) reduced root vigor by 19.31% and 76.81%, respectively. In a similar pattern, the electron transfer rate in leaves remained stable under low Al levels but significantly decreased under high Al conditions. Transcriptomic analysis showed a downregulation of genes associated with DNA replication in both Al-deficient and Al-toxic conditions, suggesting that Al may play an essential role in maintaining genomic stability during tea plant growth. Weighted gene co-expression network analysis (WGCNA) identified 84 hub genes potentially involved in Al tolerance, including aluminum sensitive 3 ( CsALS3 ), xyloglucan endotransglucosylase/hydrolase protein 23 ( CsXTH23 ), and arginine decarboxylase 2 ( CsADC2 ). Metabolomic analysis revealed that high Al concentrations suppressed pathways related to amino acid, lipid, and carbohydrate metabolism, yet several metabolites, such as putrescine, histidine, and epigallocatechin, were upregulated under high Al conditions. Combined pathway analysis indicated an upregulation of the putrescine biosynthetic pathway under high Al, highlighting its critical role in Al detoxification in tea plants. Overall, this study provides a comprehensive understanding of effects from Al on tea plant physiology, offering molecular and physiological insights into Al tolerance mechanisms and theoretical bases for optimizing tea cultivation in acidic soils.