Computational metabolomics illuminates the lineage-specific diversification of resin glycoside acylsugars in the morning glory (Convolvulaceae) family
Computational metabolomics illuminates the lineage-specific diversification of resin glycoside acylsugars in the morning glory (Convolvulaceae) family
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DOI：
10.1101/2021.08.20.457031
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发表时间：
2021-08
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通讯作者：
Lars H. Kruse;Alexandra A. Bennett;Elizabeth H. Mahood;Elena Lazarus;Se Jin Park;F. Schroeder;G. Moghe
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作者：
Lars H. Kruse;Alexandra A. Bennett;Elizabeth H. Mahood;Elena Lazarus;Se Jin Park;F. Schroeder;G. Moghe
酰基糖是一类在许多远亲家族中产生的植物防御化合物。牵牛花（旋花科）家族的成员产生不同的酰基糖亚类，称为树脂糖苷（RGs），包括低聚糖核，羟基酰基链，以及装饰脂肪和芳香酰基链。虽然许多RG结构被表征，但该纲在不同属和种中的结构多样性程度尚不清楚。在这项研究中，我们询问在不同的旋花科物种中是否存在RG结构的谱系特异性多样化，这可能表明潜在的生物合成途径的多样化。采用液相色谱-串联质谱法（LC-MS/MS）对26种植物的根和叶提取物进行系统发育分析。LC-MS/MS发现了数千个具有特征RG片段模式的峰，一个物种产生超过300个信号，反映了茄科类型酰基糖的多样性。利用核磁共振波谱技术对一种新型的银双蒿RG进行了表征，证实了之前观察到的RG具有开放的羟基酰基链而不是封闭的内酯环结构。在糖、羟基酰基链和装饰酰基链的利用上发现了大量的谱系特异性分化，特别是在旋花科中最大的两个属——易普麦属和旋花属之间。采用基于计算的知识策略，我们进一步开发了一个高查全率的工作流程，成功地解释了72%的MS/MS片段，预测了11/13个先前表征的RGs的结构成分，并部分注释了45%的RGs。本研究提高了我们对植物化学多样性的认识，为研究植物化学多样性的进化机制奠定了基础。
Acylsugars are a class of plant defense compounds produced across many distantly related families. Members of the horticulturally important morning glory (Convolvulaceae) family produce a diverse sub-class of acylsugars called resin glycosides (RGs), which comprise oligosaccharide cores, hydroxyacyl chain(s), and decorating aliphatic and aromatic acyl chains. While many RG structures are characterized, the extent of structural diversity of this class in different genera and species is not known. In this study, we asked whether there has been lineage-specific diversification of RG structures in different Convolvulaceae species that may suggest diversification of the underlying biosynthetic pathways. Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) was performed from root and leaf extracts of 26 species sampled in a phylogeny-guided manner. LC-MS/MS revealed thousands of peaks with signature RG fragmentation patterns with one species producing over 300 signals, mirroring the diversity in Solanaceae-type acylsugars. A novel RG from Dichondra argentea was characterized using Nuclear Magnetic Resonance spectroscopy, supporting previous observations of RGs with open hydroxyacyl chains instead of closed macrolactone ring structures. Substantial lineage-specific differentiation in utilization of sugars, hydroxyacyl chains, and decorating acyl chains was discovered, especially among Ipomoea and Convolvulus – the two largest genera in Convolvulaceae. Adopting a computational, knowledge-based strategy, we further developed a high-recall workflow that successfully explained ~72% of the MS/MS fragments, predicted the structural components of 11/13 previously characterized RGs, and partially annotated ~45% of the RGs. Overall, this study improves our understanding of phytochemical diversity and lays a foundation for characterizing the evolutionary mechanisms underlying RG diversification.