Key Laboratory of Tea Science of Ministry of Education, College of Horticulture, Hunan Agricultural University, Changsha 410011, China.
State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, Hefei 230036, China.
Int J Mol Sci. 2023 Feb 27;24(5):4640. doi: 10.3390/ijms24054640.
Tea plants have adapted to grow in tropical acidic soils containing high concentrations of aluminum (Al) and fluoride (F) (as Al/F hyperaccumulators) and use secret organic acids (OAs) to acidify the rhizosphere for acquiring phosphorous and element nutrients. The self-enhanced rhizosphere acidification under Al/F stress and acid rain also render tea plants prone to accumulate more heavy metals and F, which raises significant food safety and health concerns. However, the mechanism behind this is not fully understood. Here, we report that tea plants responded to Al and F stresses by synthesizing and secreting OAs and altering profiles of amino acids, catechins, and caffeine in their roots. These organic compounds could form tea-plant mechanisms to tolerate lower pH and higher Al and F concentrations. Furthermore, high concentrations of Al and F stresses negatively affected the accumulation of tea secondary metabolites in young leaves, and thereby tea nutrient value. The young leaves of tea seedlings under Al and F stresses also tended to increase Al and F accumulation in young leaves but lower essential tea secondary metabolites, which challenged tea quality and safety. Comparisons of transcriptome data combined with metabolite profiling revealed that the corresponding metabolic gene expression supported and explained the metabolism changes in tea roots and young leaves via stresses from high concentrations of Al and F. The study provides new insight into Al- and F-stressed tea plants with regard to responsive metabolism changes and tolerance strategy establishment in tea plants and the impacts of Al/F stresses on metabolite compositions in young leaves used for making teas, which could influence tea nutritional value and food safety.
茶树适应在富含铝（Al）和氟（F）的热带酸性土壤中生长（作为 Al/F 超积累植物），并利用分泌的有机酸（OAs）酸化根际以获取磷和其他元素养分。在 Al/F 胁迫和酸雨的作用下，自我增强的根际酸化也使茶树更容易积累更多的重金属和 F，这引起了人们对食品安全和健康的极大关注。然而，其背后的机制尚未完全阐明。在这里，我们报告称，茶树通过合成和分泌 OAs 以及改变其根部的氨基酸、儿茶素和咖啡因的图谱来应对 Al 和 F 胁迫。这些有机化合物可以形成茶树耐受低 pH 值和高 Al 和 F 浓度的机制。此外，高浓度的 Al 和 F 胁迫会对幼叶中茶叶次生代谢物的积累产生负面影响，从而降低茶叶的营养价值。在 Al 和 F 胁迫下，茶树幼苗的幼叶也倾向于增加 Al 和 F 在幼叶中的积累，同时降低必需的茶叶次生代谢物，这对茶叶的品质和安全构成了挑战。转录组数据与代谢物图谱的比较表明，相应的代谢基因表达通过 Al 和 F 的胁迫，为茶树根系和幼叶中的代谢变化提供了支持和解释。该研究为 Al 和 F 胁迫下的茶树提供了新的见解，揭示了茶树对代谢变化的响应机制和耐受策略的建立，以及 Al/F 胁迫对用于制茶的幼叶代谢物组成的影响，这可能会影响茶叶的营养价值和食品安全。
