The tea plant is an economically important woody beverage crop. The unique taste of tea is evoked by certain metabolites, especially catechin esters, whereas their precise formation mechanism in different cell types remains unclear. Here, a fast protoplast isolation method was established and the transcriptional profiles of 16 977 single cells from 1st and 3rd leaves were investigated. We first identified 79 marker genes based on six isolated tissues and constructed a transcriptome atlas, mapped developmental trajectories and further delineated the distribution of different cell types during leaf differentiation and genes associated with cell fate transformation. Interestingly, eight differently expressed genes were found to co-exist at four branch points. Genes involved in the biosynthesis of certain metabolites showed cell- and development-specific characteristics. An unexpected catechin ester glycosyltransferase was characterized for the first time in plants by a gene co-expression network in mesophyll cells. Thus, the first single-cell transcriptional landscape in woody crop leave was reported and a novel metabolism pathway of catechin esters in plants was discovered.

中文翻译：

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单细胞转录组图谱揭示茶叶中儿茶素酯的发育轨迹和新的代谢途径

茶树是一种经济上重要的木质饮料作物。茶的独特味道是由某些代谢物引起的，尤其是儿茶素酯，而它们在不同细胞类型中的确切形成机制仍不清楚。在这里，建立了一种快速原生质体分离方法，并研究了来自第 1 片和第 3 片叶子的 16 977 个单细胞的转录谱。我们首先基于六个分离的组织鉴定了 79 个标记基因，并构建了转录组图谱，绘制了发育轨迹，并进一步描绘了叶片分化过程中不同细胞类型的分布以及与细胞命运转化相关的基因。有趣的是，发现八个不同表达的基因在四个分支点共存。参与某些代谢物生物合成的基因表现出细胞和发育特异性特征。通过叶肉细胞中的基因共表达网络首次在植物中表征了一种意想不到的儿茶素酯糖基转移酶。因此，首次报道了木本作物叶片中的单细胞转录景观，并发现了植物中儿茶素酯的新代谢途径。