Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture and Rural Affairs of the People's Republic of China/National Center for Tea Improvement/Tea Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou, China.
Sanya Institute, Hainan Academy of Agricultural Sciences, Sanya, Hainan, China.
Physiol Plant. 2023 Nov-Dec;175(6):e14064. doi: 10.1111/ppl.14064.
Green tea made from albino buds and leaves has a strong umami taste and aroma. The cultivar 'Zhonghuang 2' (ZH2, Camellia sinensis) is a natural mutant with young shoots that are yellow in spring and green or yellow-green in summer. However, the mechanism of leaf color change remains unclear. Here, we found that young shoots of ZH2 were yellow at low temperature (LT) and green at high temperature (HT), indicating that ZH2 is a temperature-sensitive cultivar. Transmission electron microscopy analysis showed that the grana in the chloroplasts of young shoots grown at LT were poorly stacked, which caused a lack of photoreactions and chlorophyll. RNA-seq results showed 1279 genes differentially expressed in the young shoots grown at LT compared with those at HT, including genes related to cytochrome synthesis, chloroplast development, photosynthesis, and DNA methylation. A whole-genome bisulfite sequencing assay revealed that the dynamics of DNA methylation levels in the CG, CHG, and CHH contexts decreased under LT, and the change was most obvious in the CHH context. Furthermore, 72 genes showed significant changes in both expression and DNA methylation levels, and most of them were related to cytochrome synthesis, chloroplast development, photosynthesis, transcription factors, and signaling pathways. These results demonstrate that DNA methylation is involved in the LT-regulated albino processes of ZH2. Changes in DNA methylation levels were associated with changes in gene expression levels, affecting the structure and function of chloroplasts, which may have a phenotypic impact on shoot and leaf color.
由白化芽和叶片制成的绿茶具有强烈的鲜味和香气。品种‘中黄 2 号’（ZH2，茶树）是一种天然突变体，其春梢在春季呈黄色，夏季呈绿色或黄绿相间。然而，叶片颜色变化的机制尚不清楚。在这里，我们发现 ZH2 的新梢在低温（LT）下呈黄色，在高温（HT）下呈绿色，这表明 ZH2 是一种对温度敏感的品种。透射电子显微镜分析表明，在 LT 下生长的新梢的叶绿体中的类囊体堆叠不良，这导致光反应和叶绿素缺乏。RNA-seq 结果表明，在 LT 下生长的新梢与在 HT 下生长的新梢相比，有 1279 个基因差异表达，包括与细胞色素合成、叶绿体发育、光合作用和 DNA 甲基化相关的基因。全基因组亚硫酸氢盐测序分析表明，CG、CHG 和 CHH 背景下的 DNA 甲基化水平在 LT 下呈下降趋势，在 CHH 背景下变化最明显。此外，有 72 个基因在表达和 DNA 甲基化水平上均表现出显著变化，其中大多数与细胞色素合成、叶绿体发育、光合作用、转录因子和信号通路有关。这些结果表明，DNA 甲基化参与了 ZH2 的 LT 调控白化过程。DNA 甲基化水平的变化与基因表达水平的变化有关，影响叶绿体的结构和功能，这可能对芽和叶片颜色产生表型影响。
