Strigolactones (SLs), a class of plant apocarotenoids, serve dual roles as rhizosphere-signaling molecules and plant hormones. Orobanchol, a major naturally occurring SL, along with its various derivatives, has been detected in the root exudates of plants of the Fabaceae family. Medicaol, fabacyl acetate, and orobanchyl acetate were identified in the root exudates of barrel medic (Medicago truncatula), pea (Pisum sativum), and cowpea (Vigna unguiculata), respectively. Although the biosynthetic pathway leading to orobanchol production has been elucidated, the biosynthetic pathways of the orobanchol derivatives have not yet been fully elucidated. Here, we report the identification of 2-oxoglutarate-dependent dioxygenases (DOXs) and BAHD acyltransferases responsible for converting orobanchol to these derivatives in Fabaceae plants. First, the metabolic pathways downstream of orobanchol were analyzed using substrate feeding experiments. Prohexadione, an inhibitor of DOX inhibits the conversion of orobanchol to medicaol in barrel medic. The DOX inhibitor also reduced the formation of fabacyl acetate and fabacol, a precursor of fabacyl acetate, in pea. Subsequently, we utilized a dataset based on comparative transcriptome analysis to select a candidate gene encoding DOX for medicaol synthase in barrel medic. Recombinant proteins of the gene converted orobanchol to medicaol. The candidate genes encoding DOX and BAHD acyltransferase for fabacol synthase and fabacol acetyltransferase, respectively, were selected by co-expression analysis in pea. The recombinant proteins of the candidate genes converted orobanchol to fabacol and acetylated fabacol. Furthermore, fabacol acetyltransferase and its homolog in cowpea acetylated orobanchol. The kinetics and substrate specificity analyses revealed high affinity and strict recognition of the substrates of the identified enzymes. These findings shed light on the molecular mechanisms underlying the structural diversity of SLs.

中文翻译：

---

2-酮戊二酸依赖性双加氧酶和 BAHD 酰基转移酶驱动豆科植物中列班胆碱的结构多样化

独脚金内酯 (SL) 是一类植物类胡萝卜素，具有根际信号分子和植物激素的双重作用。列班胆碱 (Orobanchol) 是一种主要的天然 SL 及其各种衍生物，已在豆科植物的根部分泌物中检测到。在桶药草的根部分泌物中鉴定出 Medicaol、醋酸豆酯和醋酸草班奇酯 (蒺藜苜蓿), 豌豆 (豌豆)和豇豆（野豌豆）， 分别。尽管导致列班胆生成的生物合成途径已被阐明，但列班胆衍生物的生物合成途径尚未完全阐明。在这里，我们报告了在豆科植物中负责将列班胆碱转化为这些衍生物的 2-酮戊二酸依赖性双加氧酶 (DOX) 和 BAHD 酰基转移酶的鉴定。首先，使用底物饲喂实验分析了列班胆碱下游的代谢途径。调环酮 (Prohexadione) 是一种 DOX 抑制剂，可抑制桶内药中奥罗班胆 (Orobanchol) 转化为药物 (medicaol)。 DOX 抑制剂还减少了豌豆中乙酸豆酯和乙酸豆酯的前体豆酯醇的形成。随后，我们利用基于比较转录组分析的数据集来选择桶医学中医学合成酶的编码 DOX 的候选基因。该基因的重组蛋白将列班胆碱转化为药物。通过豌豆中的共表达分析，选择分别编码蚕豆酚合酶和蚕豆酚乙酰转移酶的DOX和BAHD酰基转移酶的候选基因。候选基因的重组蛋白将列班酚转化为蚕豆酚和乙酰化蚕豆酚。此外，豇豆中的蚕豆酚乙酰转移酶及其同系物乙酰化了列班胆。动力学和底物特异性分析揭示了所鉴定酶的底物的高亲和力和严格识别。这些发现揭示了 SL 结构多样性背后的分子机制。