College of Horticulture Science, South China Agricultural University, Guangzhou 510640, China.
Center of Experimental Teaching for Common Basic Courses, South China Agricultural University, Guangzhou 510640, China.
Molecules. 2019 Mar 18;24(6):1064. doi: 10.3390/molecules24061064.
Almost all flowers of the tea plant () are white, which has caused few researchers to pay attention to anthocyanin accumulation and color changing in tea flowers. A new purple-leaf cultivar, Baitang purple tea (BTP) was discovered in the Baitang Mountains of Guangdong, whose flowers are naturally pink, and can provide an opportunity to understand anthocyanin metabolic networks and flower color development in tea flowers. In the present study, twelve anthocyanin components were identified in the pink tea flowers, namely cyanidin -syringic acid, petunidin 3--glucoside, pelargonidin 3--beta-d-glucoside, which marks the first time these compounds have been found in the tea flowers. The presence of these anthocyanins seem most likely to be the reason for the pink coloration of the flowers. Twenty-one differentially expressed genes (DEGs) involved in anthocyanin pathway were identified using KEGG pathway functional enrichment, and ten of these DEG's screened using venn and KEGG functional enrichment analysis during five subsequent stages of flower development. By comparing DEGs and their expression levels across multiple flower development stages, we found that anthocyanin biosynthesis and accumulation in BTP flowers mainly occurred between the third and fourth stages (BTP3 to BTP4). Particularly, during the period of peak anthocyanin synthesis 17 structural genes were upregulated, and four structural genes were downregulated only. Ultimately, eight critical genes were identified using weighted gene co-expression network analysis (WGCNA), which were found to have direct impact on biosynthesis and accumulation of three flavonoid compounds, namely cyanidin 3--glucoside, petunidin 3--glucoside and epicatechin gallate. These results provide useful information about the molecular mechanisms of coloration in rare pink tea flower of anthocyanin-rich tea, enriching the gene resource and guiding further research on anthocyanin accumulation in purple tea.
几乎所有的茶树（）花都是白色的，这导致很少有研究人员关注茶叶花中的花青苷积累和颜色变化。在广东的白塘山发现了一个新的紫叶品种，白塘紫茶（BTP），其花朵自然呈粉红色，为了解茶叶花中的花青苷代谢网络和花色发育提供了机会。本研究在粉红色的茶花中鉴定出 12 种花青苷成分，即矢车菊-丁香酸、飞燕草素 3-葡萄糖苷、天竺葵素 3-β-葡萄糖苷，这标志着这些化合物首次在茶叶花中被发现。这些花青苷的存在似乎是花朵呈粉红色的最主要原因。通过 KEGG 途径功能富集，鉴定出 21 个参与花青苷途径的差异表达基因（DEG），通过 venn 和 KEGG 功能富集分析在随后的五个花发育阶段筛选出其中的 10 个 DEG。通过比较多个花发育阶段的 DEG 和它们的表达水平，我们发现 BTP 花中的花青苷生物合成和积累主要发生在第三和第四阶段（BTP3 到 BTP4）。特别是在花青苷合成高峰期，有 17 个结构基因上调，只有 4 个结构基因下调。最终，通过加权基因共表达网络分析（WGCNA）鉴定出 8 个关键基因，它们直接影响三种类黄酮化合物，即矢车菊素 3-葡萄糖苷、飞燕草素 3-葡萄糖苷和表儿茶素没食子酸酯的生物合成和积累。这些结果为富含花青苷的珍稀粉红色茶花花色形成的分子机制提供了有用的信息，丰富了基因资源，指导了进一步对紫茶花青苷积累的研究。
