The medicinal value of the monoterpenoid indole alkaloids (MIAs) such as 3',4'-anhydrovinblastine, as well as their chemical complexity have stimulated extensive efforts to understand the biochemical and molecular pathways involved in their biosynthesis in plants such as Catharanthus roseus, Rawvolfia serpentina and others. Ethyl methane sulphonate (EMS) mutagenesis has been used successfully together with simple MIA thin layer chromatography screening to identify C. roseus mutants with altered MIA profiles. This study describes the isolation of very low iridoid and MIA containing C. roseus mutant (M2-1582) that accumulates MIAs when the plant is provided with secologanin by feeding mutant roots or by grafting the mutant scion onto wild type roots. The observed low iridoid and MIA content was correlated with lowered expression of BIS1/BIS2 transcription factors and several genes involved in secologanin biosynthesis that are expressed in internal phloem parenchyma cells of leaves. When exogenous secologanin was applied to the roots of the mutant plant, secologanin levels rose more than 13-fold, while two major MIAs catharanthine and vindoline rose more than 8- and 4- fold, respectively. Grafting the mutant on WT stocks led to 27-, 11- and 27-fold increases in secologanin, catharanthine and vindoline, respectively in leaves of the scion one week after graft initiation. Other minor MIAs (serpentine, anhydrovinblastine, vindolidine, deacetylvindoline, tabersonine and 16-methoxytabersonine) that were not detected in the mutant, became detectable in leaves of the scion. These results provide strong evidence for a secologanin transport mechanism that mobilizes this iridoid between different plant organs in C. roseus and that secologanin transport to the mutant across the graft union permits the formation of MIAs in leaves of the mutant.

中文翻译：

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secologanin 的器官间转运允许在长春花突变体中组装单萜吲哚生物碱

单萜吲哚生物碱 (MIA) 的药用价值，如 3',4'-脱水长春碱，以及它们的化学复杂性，激发了人们对它们在长春花、罗夫沃尔菲亚等植物中生物合成所涉及的生化和分子途径的广泛研究蛇纹石等。甲基磺酸乙酯 (EMS) 诱变已成功地与简单的 MIA 薄层色谱筛选一起使用，以识别具有改变 MIA 配置文件的 C.roseus 突变体。本研究描述了极低环烯醚萜类化合物和含有 MIA 的 C. roseus 突变体 (M2-1582) 的分离，当通过喂养突变体根或通过将突变体接穗嫁接到野生型根上为植物提供 secologanin 时，该突变体会积累 MIA。观察到的环烯醚萜类化合物和 MIA 含量低与 BIS1/BIS2 转录因子的表达降低有关，以及叶片内部韧皮部薄壁组织中表达的参与节藻素生物合成的几个基因的表达降低。将外源性secologanin 应用于突变植物的根部时，secologanin 水平上升了13 倍以上，而两种主要的MIAs 长春花碱和vindoline 分别上升了8 倍和4 倍以上。在 WT 原种上嫁接突变体导致接穗开始一周后接穗叶中的 secologanin、长春花碱和文多林分别增加 27、11 和 27 倍。在突变体中未检测到的其他次要 MIA（蛇纹石、脱水长春碱、文多利定、脱乙酰文多林、泰伯宁和 16-甲氧基泰伯宁）在接穗的叶子中变得可检测。