College of Life Sciences, Northwest A & F University, Yangling, People's Republic of China.
PLoS One. 2013 Sep 10;8(9):e73259. doi: 10.1371/journal.pone.0073259. eCollection 2013.
Salvia miltiorrhiza Bunge is one of the most renowned traditional medicinal plants in China. Phenolic acids that are derived from the rosmarinic acid pathway, such as rosmarinic acid and salvianolic acid B, are important bioactive components in S. miltiorrhiza. Accumulations of these compounds have been reported to be induced by various elicitors, while little is known about transcription factors that function in their biosynthetic pathways. We cloned a subgroup 4 R2R3 MYB transcription factor gene (SmMYB39) from S. miltiorrhiza and characterized its roles through overexpression and RNAi-mediated silencing. As the results showed, the content of 4-coumaric acid, rosmarinic acid, salvianolic acid B, salvianolic acid A and total phenolics was dramatically decreased in SmMYB39-overexpressing S. miltiorrhiza lines while being enhanced by folds in SmMYB39-RNAi lines. Quantitative real-time PCR and enzyme activities analyses showed that SmMYB39 negatively regulated transcripts and enzyme activities of 4-hydroxylase (C4H) and tyrosine aminotransferase (TAT). These data suggest that SmMYB39 is involved in regulation of rosmarinic acid pathway and acts as a repressor through suppressing transcripts of key enzyme genes.
丹参是中国最著名的传统药用植物之一。迷迭香酸途径衍生的酚酸类化合物，如迷迭香酸和丹酚酸 B，是丹参中的重要生物活性成分。据报道，这些化合物的积累是由各种诱导子诱导的，而关于在其生物合成途径中起作用的转录因子知之甚少。我们从丹参中克隆了一个 R2R3 MYB 转录因子基因亚组 4（SmMYB39），并通过过表达和 RNAi 介导的沉默来表征其作用。结果表明，SmMYB39 过表达的丹参中 4-咖啡酸、迷迭香酸、丹酚酸 B、丹酚酸 A 和总酚含量显著降低，而 SmMYB39-RNAi 系中则增加了几倍。定量实时 PCR 和酶活性分析表明，SmMYB39 负调控 4-羟化酶（C4H）和酪氨酸转氨酶（TAT）的转录本和酶活性。这些数据表明，SmMYB39 参与迷迭香酸途径的调控，并通过抑制关键酶基因的转录本作为阻遏物起作用。
