Man Jinhui, Shi Yue, Huang Yuying, Zhang Xiaoqin, Wang Xin, Liu Shanhu, He Gaojie, An Kelu, Han Dongran, Wang Xiaohui, Wei Shengli
School of Chinese Materia Medica, Beijing University of Chinese Medicine, Beijing 102488, China.
School of Life and Science, Beijing University of Chinese Medicine, Beijing 102488, China.
Hortic Res. 2023 Jul 5;10(8):uhad134. doi: 10.1093/hr/uhad134. eCollection 2023 Aug.
Saponins are the main triterpenoid ingredients from , a well-known Chinese medicine, and are important sources for producing drugs to prevent and treat cerebrovascular and cardiovascular diseases. However, the transcriptional regulatory network of saponin biosynthesis in is largely unknown. In the present study we demonstrated that one R2R3-MYB transcription factor, designated , acts as a repressor of saponin accumulation. Suppression of in calli significantly increased the saponin content and the expression level of saponin biosynthetic genes. PnMYB4 directly bound to the promoters of key saponin biosynthetic genes, including , , and , to repress saponin accumulation. PnMYB4 and the activator PnMYB1 could interacted with PnbHLH, which is a positive regulator of saponin biosynthesis, to modulate the biosynthesis of saponin. PnMYB4 competed with PnMYB1 for binding to PnbHLH, repressing activation of the promoters of saponin structural genes induced by the PnMYB1-PnbHLH complex. Our study reveals that a complex regulatory module of saponin biosynthesis is associated with positive and negative MYB transcriptional regulators and provides a theoretical basis for improving the content of saponins and efficacy of .
皂苷是一种著名的中药中的主要三萜类成分，是生产预防和治疗心脑血管疾病药物的重要来源。然而，该中药中皂苷生物合成的转录调控网络在很大程度上尚不清楚。在本研究中，我们证明了一种名为PnMYB4的R2R3-MYB转录因子作为皂苷积累的抑制因子。在愈伤组织中抑制PnMYB4显著提高了皂苷含量和皂苷生物合成基因的表达水平。PnMYB4直接与关键皂苷生物合成基因（包括PnSS、PnSE和PnCAS）的启动子结合，以抑制皂苷积累。PnMYB4与激活因子PnMYB1可与皂苷生物合成的正调控因子PnbHLH相互作用，从而调节皂苷的生物合成。PnMYB4与PnMYB1竞争结合PnbHLH，抑制由PnMYB1-PnbHLH复合物诱导的皂苷结构基因启动子的激活。我们的研究揭示了一个与正负MYB转录调节因子相关的复杂皂苷生物合成调控模块，并为提高皂苷含量和该中药的功效提供了理论依据。
