Key Laboratory of Tea Science of Ministry of Education, Hunan Agricultural University, Changsha 410128, PR China.
Key Laboratory of Tea Science of Ministry of Education, Hunan Agricultural University, Changsha 410128, PR China; National Research Center of Engineering and Technology for Utilization of Botanical Functional Ingredients & Hunan Co-innovation Center for Utilization of Botanical Functional Ingredients, Hunan Agricultural University, Changsha 410128, PR China.
Gene. 2019 May 30;699:8-15. doi: 10.1016/j.gene.2019.03.002. Epub 2019 Mar 6.
Epigallocatechin-3-O-(3-O-methyl) gallate (EGCG3"Me) in tea (Camellia sinensis (L.) O. Kuntze) is a major source of O-methylated catechin and renowned for a wide range of health effects. However, the transcriptional regulation mechanisms of EGCG3"Me biosynthesis remain unclear. In the present work, the basic Helix-Loop-Helix (bHLH) transcription factor, designated as CsbHLH62, belonging to GBOF group of bHLH families, was isolated and characterized from Camellia sinensis. CsbHLH62 contains an Open Reading Frame of 1662 bp and encodes a polypeptide of 553 amino acids. Subcellular location and transcriptional activity analysis showed it as a nucleus protein and possessed transcriptional inhibition activity. Furthermore, the expression of CsbHLH62 was decreased during EGCG3"Me accumulation. More importantly, E-box motifs (5'-CANNTG-3') were found in the promoters of CCoAOMT, CsLAR, and CsDFR, and further transient expression assays showed that CsbHLH62 repressed the transcription of CCoAOMT, CsLAR, and CsDFR. Collectively, these results suggest that CsbHLH62 acts as a transcriptional repressor that might be negatively affecting the accumulation of EGCG3"Me. These findings provide novel insights into the regulatory mechanism of EGCG3"Me biosynthesis, which might help to breed high EGCG3"Me-content tea plants.
表没食子儿茶素-3-O-(3-O-甲基)没食子酸酯（EGCG3"Me）在茶（Camellia sinensis (L.) O. Kuntze）中是 O-甲基化儿茶素的主要来源，以其广泛的健康功效而闻名。然而，EGCG3"Me 生物合成的转录调控机制尚不清楚。在本工作中，从茶树中分离并鉴定了一个属于 GBOF 家族 bHLH 家族的基本螺旋-环-螺旋（bHLH）转录因子，命名为 CsbHLH62。CsbHLH62 含有一个 1662bp 的开放阅读框，编码一个 553 个氨基酸的多肽。亚细胞定位和转录活性分析表明它是一种核蛋白，具有转录抑制活性。此外，在 EGCG3"Me 积累过程中 CsbHLH62 的表达降低。更重要的是，在 CCoAOMT、CsLAR 和 CsDFR 的启动子中发现了 E-box 基序（5'-CANNTG-3'），进一步的瞬时表达分析表明 CsbHLH62 抑制了 CCoAOMT、CsLAR 和 CsDFR 的转录。综上所述，这些结果表明 CsbHLH62 作为一个转录抑制因子，可能会对 EGCG3"Me 的积累产生负面影响。这些发现为 EGCG3"Me 生物合成的调控机制提供了新的见解，可能有助于培育高 EGCG3"Me 含量的茶树。
