C13-apocarotenoids (norisoprenoids) are carotenoid-derived oxidation products, which perform important physiological functions in plants. Although their biosynthetic pathways have been extensively studied, their metabolism including glycosylation remains elusive. Candidate uridine-diphosphate glycosyltransferase genes (UGTs) were selected for their high transcript abundance in comparison with other UGTs in vegetative tissues of Nicotiana benthamiana and Mentha × piperita, as these tissues are rich sources of apocarotenoid glucosides. Hydroxylated C13-apocarotenol substrates were produced by P450-catalyzed biotransformation and microbial/plant enzyme systems were established for the synthesis of glycosides. Natural substrates were identified by physiological aglycone libraries prepared from isolated plant glycosides. In total, we identified six UGTs that catalyze the unprecedented glucosylation of C13-apocarotenols, where glucose is bound either to the cyclohexene ring or butane side chain. MpUGT86C10 is a superior novel enzyme that catalyzes the glucosylation of allelopathic 3-hydroxy-α-damascone, 3-oxo-α-ionol, 3-oxo-7,8-dihydro-α-ionol (Blumenol C) and 3-hydroxy-7,8-dihydro-β-ionol, while a germination test demonstrated the higher phytotoxic potential of a norisoprenoid glucoside in comparison to its aglycone. Glycosylation of C13-apocarotenoids has several functions in plants, including increased allelopathic activity of the aglycone, facilitating exudation by roots and allowing symbiosis with arbuscular mycorrhizal fungi. The results enable in-depth analyses of the roles of glycosylated norisoprenoid allelochemicals, the physiological functions of apocarotenoids during arbuscular mycorrhizal colonization and the associated maintenance of carotenoid homeostasis.

中文翻译：

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烟草本氏烟和薄荷（Mentha×piperita）中具有生物活性的C13-apocar​​otenol的糖基化作用。

C13-类胡萝卜素（类异戊二烯类）是类胡萝卜素衍生的氧化产物，在植物中发挥重要的生理功能。尽管已对其生物合成途径进行了广泛研究，但其代谢（包括糖基化）仍然难以捉摸。相比本底烟草和薄荷（Mentha×piperita）营养组织中的其他UGT，我们选择了候选尿苷二磷酸糖基转移酶基因（UGTs），因为它们具有较高的转录本丰富度，因为这些组织是类胡萝卜素类糖苷的丰富来源。通过P450催化的生物转化产生羟基化的C13-apocar​​otenol底物，并建立了用于合成糖苷的微生物/植物酶系统。通过从分离的植物糖苷制备的生理性糖苷配基文库鉴定天然底物。总共，我们鉴定了六种UGT，它们能催化C13-厚朴酚的空前糖基化，其中葡萄糖与环己烯环或丁烷侧链结合。MpUGT86C10是一种出色的新型酶，可催化化感性3-羟基-α-大马酮，3-氧代-α-紫罗兰，3-氧代-7,8-二氢-α-紫罗兰（Blumenol C）和3-羟基- 7,8-二氢-β-紫罗兰醇，而发芽测试表明，去甲肾上腺素类苷比其糖苷配基具有更高的植物毒性潜力。C13-类胡萝卜素的糖基化在植物中具有多种功能，包括糖苷配基的化感活性增强，促进根部渗出并允许与丛枝菌根真菌共生。结果使我们能够深入分析糖基化类异戊二烯类化感物质的作用，