Shanghai Key Laboratory of Plant Functional Genomics and Resources, Shanghai Chenshan Botanical Garden, Shanghai 201602, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Plant Physiol. 2022 Mar 4;188(3):1496-1506. doi: 10.1093/plphys/kiab567.
Tanshinone ⅡA (TⅡA), a diterpene quinone with a furan ring, is a bioactive compound found in the medicinal herb redroot sage (Salvia miltiorrhiza Bunge), in which both furan and dihydrofuran analogs are present in abundance. Progress has been made recently in elucidating the tanshinone biosynthetic pathway, including heterocyclization of the dihydrofuran D-ring by cytochrome P450s; however, dehydrogenation of dihydrofuran to furan, a key step of furan ring formation, remains uncharacterized. Here, by differential transcriptome mining, we identified six 2-oxoglutarate-dependent dioxygenase (2-ODD) genes whose expressions corresponded to tanshinone biosynthesis. We showed that Sm2-ODD14 acts as a dehydrogenase catalyzing the furan ring aromatization. In vitro Sm2-ODD14 converted cryptotanshinone to TⅡA and thus was designated TⅡA synthase (SmTⅡAS). Furthermore, SmTⅡAS showed a strict substrate specificity, and repression of SmTⅡAS expression in hairy root by RNAi led to increased accumulation of total dihydrofuran-tanshinones and decreased production of furan-tanshinones. We conclude that SmTⅡAS controls the metabolite flux from dihydrofuran- to furan-tanshinones, which influences medicinal properties of S. miltiorrhiza.
丹参酮ⅡA（TⅡA）是一种具有呋喃环的二萜醌，是药用植物丹参（Salvia miltiorrhiza Bunge）中的一种生物活性化合物，其中呋喃和二氢呋喃类似物都大量存在。最近在阐明丹参酮生物合成途径方面取得了进展，包括细胞色素 P450 介导的二氢呋喃 D 环杂环化；然而，二氢呋喃脱氢形成呋喃，这是呋喃环形成的关键步骤，仍然没有特征。在这里，通过差异转录组挖掘，我们鉴定了六个 2-氧戊二酸依赖性双加氧酶（2-ODD）基因，它们的表达与丹参酮生物合成相对应。我们表明 Sm2-ODD14 作为一种脱氢酶起作用，催化呋喃环的芳构化。体外 Sm2-ODD14 将隐丹参酮转化为 TⅡA，因此被指定为 TⅡA 合酶（SmTⅡAS）。此外，SmTⅡAS 表现出严格的底物特异性，通过 RNAi 抑制毛状根中的 SmTⅡAS 表达导致总二氢呋喃-丹参酮的积累增加，而呋喃-丹参酮的产生减少。我们得出结论，SmTⅡAS 控制着从二氢呋喃到呋喃丹参酮的代谢物通量，这影响了丹参的药用特性。
