Gao Chenxi, Sun Yue, Li Jing, Zhou Zhe, Deng Xuming, Wang Zhihui, Wu Shaoling, Lin Lin, Huang Yan, Zeng Wen, Lyu Shiheng, Chen Jianjun, Cao Shixian, Yu Shuntian, Chen Zhidan, Sun Weijiang, Xue Zhihui
College of Horticulture, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
Anxi College of Tea Science, Fujian Agriculture and Forestry University, Quanzhou 362400, China.
Antioxidants (Basel). 2023 Feb 6;12(2):392. doi: 10.3390/antiox12020392.
There is increasing interest in the production and consumption of tea ( L.) processed from purple-leaved cultivar due to their high anthocyanin content and health benefits. However, how and why seasonal changes affect anthocyanin accumulation in young tea leaves still remains obscured. In this study, anthocyanin and abscisic acid (ABA) contents in young leaves of Zifuxing 1 (ZFX1), a cultivar with new shoots turning to purple in Wuyi Mountain, a key tea production region in China, were monitored over four seasons. Young leaves produced in September were highly purplish, which was accompanied with higher anthocyanin and ABA contents. Among the environmental factors, the light intensity in particular was closely correlated with anthocyanin and ABA contents. A shade experiment also indicated that anthocyanin content significantly decreased after 168 h growth under 75% shade, but ABA treatment under the shade conditions sustained anthocyanin content. To confirm the involvement of ABA in the modulation of anthocyanin accumulation, anthocyanin, carotenoids, chlorophyll, ABA, jasmonic acid (JA), and salicylic acid (SA) in the young leaves of four cultivars, including ZFX1, Zijuan (ZJ), wherein leaves are completely purple, Rougui (RG) and Fudingdabaicha (FDDB) wherein leaves are green, were analyzed, and antioxidant activities of the leaf extracts were tested. Results showed that ABA, not other tested hormones, was significantly correlated with anthocyanin accumulation in the purple-leaved cultivars. Cultivars with higher anthocyanin contents exhibited higher antioxidant activities. Subsequently, ZFX1 plants were grown under full sun and treated with ABA and fluridone (Flu), an ABA inhibitor. ABA treatment elevated anthocyanin level but decreased chlorophyll contents. The reverse was true to those treated with Flu. To pursue a better understanding of ABA involvement in anthocyanin accumulation, RNA-Seq was used to analyze transcript differences among ABA- or Flu-treated and untreated ZFX1 plants. Results indicated that the differentially expressed genes in ABA or Flu treatment were mainly ABA signal sensing and metabolism-related genes, anthocyanin accumulation-related genes, light-responsive genes, and key regulatory MYB transcription factors. Taking all the results into account, a model for anthocyanin accumulation in ZFX1 cultivar was proposed: high light intensity caused reactive oxygen stress, which triggered the biosynthesis of ABA; ABA interactions with transcription factors, such as MYB-enhanced anthocyanin biosynthesis limited chlorophyll and carotenoid accumulation; and transport of anthocyanin to vacuoles resulting in the young leaves of ZFX1 with purplish coloration. Further research is warranted to test this model.
由于富含花青素且对健康有益，由紫叶品种加工而成的茶叶（L.）的生产和消费受到越来越多的关注。然而，季节性变化如何以及为何影响幼嫩茶叶中花青素的积累仍不清楚。在本研究中，对中国主要茶叶产区武夷山的紫福星1号（ZFX1）幼叶中的花青素和脱落酸（ABA）含量进行了四季监测。9月长出的幼叶呈深紫色，同时花青素和ABA含量较高。在环境因素中，光照强度尤其与花青素和ABA含量密切相关。遮荫实验还表明，在75%遮荫条件下生长168小时后，花青素含量显著降低，但在遮荫条件下进行ABA处理可维持花青素含量。为了证实ABA参与花青素积累的调控，分析了包括ZFX1、叶片完全呈紫色的紫鹃（ZJ）、叶片为绿色的肉桂（RG）和福鼎大白茶（FDDB）在内的四个品种幼叶中的花青素、类胡萝卜素、叶绿素、ABA、茉莉酸（JA）和水杨酸（SA），并测试了叶片提取物的抗氧化活性。结果表明，ABA而非其他测试激素与紫叶品种中的花青素积累显著相关。花青素含量较高的品种表现出较高的抗氧化活性。随后，将ZFX1植株种植在全光照下，并用ABA和ABA抑制剂氟啶酮（Flu）处理。ABA处理提高了花青素水平，但降低了叶绿素含量。氟啶酮处理的结果则相反。为了更好地理解ABA参与花青素积累的机制，利用RNA测序分析了ABA或氟啶酮处理与未处理的ZFX1植株之间的转录差异。结果表明，ABA或氟啶酮处理中差异表达的基因主要是ABA信号感知和代谢相关基因、花青素积累相关基因、光响应基因以及关键调控MYB转录因子。综合所有结果，提出了ZFX1品种花青素积累的模型：高光强引起活性氧胁迫，进而触发ABA的生物合成；ABA与转录因子如MYB相互作用增强花青素生物合成，限制叶绿素和类胡萝卜素积累；花青素转运到液泡导致ZFX1幼叶呈现紫色。有必要进行进一步研究来验证该模型。
