Plant Germplasm and Genomics Center, Germplasm Bank of Wild Species in Southwestern China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China; Institution of Genomics and Bioinformatics, South China Agricultural University, Guangzhou 510642, China; University of the Chinese Academy of Sciences, Beijing 100039, China.
Plant Germplasm and Genomics Center, Germplasm Bank of Wild Species in Southwestern China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China; Institution of Genomics and Bioinformatics, South China Agricultural University, Guangzhou 510642, China.
Mol Plant. 2017 Jun 5;10(6):866-877. doi: 10.1016/j.molp.2017.04.002. Epub 2017 May 2.
Tea is the world's oldest and most popular caffeine-containing beverage with immense economic, medicinal, and cultural importance. Here, we present the first high-quality nucleotide sequence of the repeat-rich (80.9%), 3.02-Gb genome of the cultivated tea tree Camellia sinensis. We show that an extraordinarily large genome size of tea tree is resulted from the slow, steady, and long-term amplification of a few LTR retrotransposon families. In addition to a recent whole-genome duplication event, lineage-specific expansions of genes associated with flavonoid metabolic biosynthesis were discovered, which enhance catechin production, terpene enzyme activation, and stress tolerance, important features for tea flavor and adaptation. We demonstrate an independent and rapid evolution of the tea caffeine synthesis pathway relative to cacao and coffee. A comparative study among 25 Camellia species revealed that higher expression levels of most flavonoid- and caffeine- but not theanine-related genes contribute to the increased production of catechins and caffeine and thus enhance tea-processing suitability and tea quality. These novel findings pave the way for further metabolomic and functional genomic refinement of characteristic biosynthesis pathways and will help develop a more diversified set of tea flavors that would eventually satisfy and attract more tea drinkers worldwide.
茶是世界上最古老、最受欢迎的含咖啡因饮料，具有巨大的经济、药用和文化价值。在这里，我们首次展示了经过高度优化的富含重复序列（80.9%）、大小为 30.2 亿碱基对的栽培茶树（Camellia sinensis）基因组的高质量核苷酸序列。研究表明，茶树拥有庞大的基因组是由少数 LTR 反转录转座子家族的缓慢、稳定和长期扩增所导致的。除了最近发生的全基因组复制事件之外，还发现了与类黄酮生物合成代谢相关的基因的谱系特异性扩张，这增强了儿茶素的产生、萜烯酶的激活和对胁迫的耐受性，这些都是茶叶风味和适应性的重要特征。我们证明了茶叶中咖啡因合成途径相对于可可和咖啡是独立且快速进化的。对 25 个山茶属物种的比较研究表明，大多数类黄酮和咖啡因但不是茶氨酸相关基因的高表达水平有助于增加儿茶素和咖啡因的产量，从而提高茶叶加工的适宜性和茶叶质量。这些新发现为进一步代谢组学和功能基因组学研究特征生物合成途径铺平了道路，并将有助于开发出更多样化的茶叶风味，最终满足并吸引更多的全球茶客。
