College of Horticulture, Fujian Agriculture and Forestry University, Shangxiadian Road 15, Cangshan District, Fuzhou, Fujian 350002, China.
Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, Fujian Agriculture and Forestry University, Shangxiadian Road 15, Cangshan District, Fuzhou, Fujian 350002, China.
Tree Physiol. 2024 Jul 2;44(7). doi: 10.1093/treephys/tpae065.
Flavonoids (especially anthocyanins and catechins) and amino acids represent a high abundance of health-promoting metabolites. Although we observed abscisic acid accumulation in purple leaves and low levels in albino tea leaves, the specific mechanism behind its impact on flavor compounds remains unclear. In this study, we treated tea leaves with exogenous abscisic acid and abscisic acid biosynthesis inhibitors (Flu), measured physiological indicators and conducted comprehensive transcriptomic and metabolomic analyses to elucidate the potential mechanisms underlying color change. Our results demonstrate that abscisic acid treatment induces purple coloration, while Flu treatment causes discoloration in tea leaves. Metabolomic analysis revealed higher levels of four anthocyanins and six catechins in the group treated with abscisic acid in comparison with the control group. Additionally, there was a notable increase in 15 amino acids in the Flu-treated group. Notably, the levels of flavonoids and amino acids showed an inverse relationship between the two treatments. Transcriptomic comparison between the treatments and the control group revealed upregulation of differentially expressed genes encoding dihydroflavonol reductase and uridine diphosphate-glycose flavonoid glycosyltransferase in the abscisic acid-treated group, leading to the accumulation of identified anthocyanins and catechins. In contrast, differentially expressed genes encoding nitrate reductase and nitrate transporter exhibited elevated expression in the group treated with Flu, consequently facilitating the accumulation of amino acids, specifically L-theanine and L-glutamine. Furthermore, our co-expression network analysis suggests that MYB and bHLH transcription factors may play crucial roles in regulating the expression of differentially expressed genes involved in the biosynthesis of flavonoids and amino acids. This study provides insights for targeted genetic engineering to enhance the nutritional and market value of tea, together with the potential application of purple and albino tea leaves as functional beverages. It also offers guidance for future breeding programs and production.
类黄酮（尤其是花色苷和儿茶素）和氨基酸代表了大量具有促进健康作用的代谢物。虽然我们观察到紫色叶片中脱落酸的积累和白化茶叶中脱落酸的低水平，但它对风味化合物影响的具体机制尚不清楚。在这项研究中，我们用外源脱落酸和脱落酸生物合成抑制剂（Flu）处理茶叶，测量生理指标，并进行全面的转录组和代谢组分析，以阐明颜色变化的潜在机制。我们的结果表明，脱落酸处理诱导了紫色着色，而 Flu 处理导致茶叶变色。代谢组分析显示，与对照组相比，脱落酸处理组的四种花色苷和六种儿茶素水平更高。此外，Flu 处理组中有 15 种氨基酸含量显著增加。值得注意的是，两种处理方式下的类黄酮和氨基酸水平呈相反关系。处理组与对照组的转录组比较显示，脱落酸处理组中编码二氢黄酮醇还原酶和尿苷二磷酸-葡萄糖黄酮糖苷基转移酶的差异表达基因上调，导致鉴定出的花色苷和儿茶素积累。相比之下，Flu 处理组中编码硝酸还原酶和硝酸盐转运体的差异表达基因表达上调，从而促进了氨基酸，特别是 L-茶氨酸和 L-谷氨酰胺的积累。此外，我们的共表达网络分析表明，MYB 和 bHLH 转录因子可能在调节与类黄酮和氨基酸生物合成相关的差异表达基因的表达中发挥关键作用。本研究为有针对性的基因工程提供了思路，以提高茶叶的营养价值和市场价值，同时为紫色和白化茶叶作为功能性饮料的潜在应用提供了指导。它还为未来的选育计划和生产提供了指导。
