Tenderness is a core index for evaluating the quality of young tea plant shoots and ultimately influences the quality and yield of tea products in terms of bioactive components, processing adaptability, tenderness-keeping ability, and other factors. In this study, we describe the underlying regulatory mechanism of tenderness changes in young shoots of tea plants, combined with biochemical composition determination and transcriptome analysis. The high accumulation of lignin, cellulose, hemicellulose, and pectin is a direct factor leading to a decrease in the tenderness of young shoots, which is dependent on the upregulated expression of genes encoding enzymes related to their biosynthesis. The accumulation of lignin during tenderness decrease in young shoots was accompanied by a decrease in the major flavonoid catechins and anthocyanins, and the upregulated expression of lignin biosynthesis-related genes was also accompanied by the downregulated expression of flavonoid biosynthesis-related genes, implying that the competition between the lignin and flavonoid biosynthesis pathways influences tenderness and bioactive component changes in young tea plant shoots. In addition, as core factors, hydroxycinnamoyl-CoA: shikimate/quinate hydroxycinnamoyl transferase (HCT) and chalcone synthase (CHS) synergize with downstream enzymes to maintain the balance between lignin and flavonoid metabolism. MYB transcription factors in the G10 and G11 groups regulated the expression of genes related to lignin and flavonoid biosynthesis pathways, respectively, and other transcription factors may also play roles in regulating this balance. This study elucidates the regulatory mechanisms of quality changes in young tea plant shoots from the perspective of tenderness.

中文翻译：

---

木质素和类黄酮代谢之间的平衡在茶树 （Camellia sinensis） 幼芽质量的变化中起着核心作用


嫩度是评价茶树幼苗嫩芽品质的核心指标，最终影响茶叶制品的品质和产量，包括生物活性成分、加工适应性、保嫩性等因素。在本研究中，我们描述了茶树幼梢嫩芽嫩度变化的潜在调控机制，并结合生化成分测定和转录组分析。木质素、纤维素、半纤维素和果胶的高积累是导致嫩芽嫩度降低的直接因素，这取决于编码与其生物合成相关的酶的基因的上调表达。幼梢减嫩过程中木质素的积累伴随着主要黄酮儿茶素和花青素的减少，木质素生物合成相关基因的表达上调也伴随着黄酮类生物合成相关基因的表达下调，表明木质素和类黄酮生物合成途径之间的竞争影响了茶树幼芽的嫩度和生物活性成分的变化。此外，作为核心因子的羟基肉桂酰辅酶 A：莽草酸盐/奎恩酸酯羟基肉桂酰转移酶 （HCT） 和查尔酮合酶 （CHS） 与下游酶协同作用，维持木质素和类黄酮代谢之间的平衡。G10 和 G11 组的 MYB 转录因子分别调控木质素和类黄酮生物合成途径相关基因的表达，其他转录因子也可能在调节这种平衡中发挥作用。本研究从嫩度的角度阐明了茶树幼苗品质变化的调控机制。