Key Message

Distinct catalytic features of the Poaceae TPS-a subfamily arose early in grass evolution and the reactions catalyzed have become more complex with time.

Abstract

The structural diversity of terpenes found in nature is mainly determined by terpene synthases (TPS). TPS enzymes accept ubiquitous prenyl diphosphates as substrates and convert them into the various terpene skeletons by catalyzing a carbocation-driven reaction. Based on their sequence similarity, terpene synthases from land plants can be divided into different subfamilies, TPS-a to TPS-h. In this study, we aimed to understand the evolution and functional diversification of the TPS-a subfamily in the Poaceae (the grass family), a plant family that contains important crops such as maize, wheat, rice, and sorghum. Sequence comparisons showed that aside from one clade shared with other monocot plants, the Poaceae TPS-a subfamily consists of five well-defined clades I–V, the common ancestor of which probably originated very early in the evolution of the grasses. A survey of the TPS literature and the characterization of representative TPS enzymes from clades I–III revealed clade-specific substrate and product specificities. The enzymes in both clade I and II function as sesquiterpene synthases with clade I enzymes catalyzing initial C10-C1 or C11-C1 ring closures and clade II enzymes catalyzing C6-C1 closures. The enzymes of clade III mainly act as monoterpene synthases, forming cyclic and acyclic monoterpenes. The reconstruction and characterization of clade ancestors demonstrated that the differences among clades I–III were already present in their ancestors. However, the ancestors generally catalyzed simpler reactions with less double-bond isomerization and fewer cyclization steps. Overall, our data indicate an early origin of key enzymatic features of TPS-a enzymes in the Poaceae, and the development of more complex reactions over the course of evolution.

中文翻译：

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祖先基因的重建和生化表征提供了对禾本科中萜烯合酶功能进化的见解。

关键信息

禾本科 TPS-a 亚科的独特催化特征出现在草进化的早期，并且催化的反应随着时间的推移变得更加复杂。

抽象的

自然界中发现的萜烯的结构多样性主要由萜烯合酶（TPS）决定。TPS 酶接受普遍存在的异戊二烯二磷酸作为底物，并通过催化碳阳离子驱动的反应将它们转化为各种萜烯骨架。基于它们的序列相似性，来自陆地植物的萜合酶可分为不同的亚科，TPS-a 到 TPS-h。在本研究中，我们旨在了解禾本科（禾本科）中 TPS 亚科的进化和功能多样化，禾本科是一种包含玉米、小麦、水稻和高粱等重要作物的植物科。序列比较表明，除了与其他单子叶植物共有的一个进化枝外，禾本科 TPS-a 亚科由五个明确定义的进化枝 I-V 组成，它们的共同祖先可能起源于草类进化的早期。对 TPS 文献的调查和来自进化枝 I-III 的代表性 TPS 酶的表征揭示了进化枝特异性底物和产物特异性。进化枝 I 和 II 中的酶作为倍半萜合酶起作用，进化枝 I 酶催化初始 C10-C1 或 C11-C1 闭环，进化枝 II 酶催化 C6-C1 闭合。进化枝 III 的酶主要作为单萜合酶，形成环状和非环状单萜。进化枝祖先的重建和表征表明，进化枝 I-III 之间的差异已经存在于他们的祖先中。然而，祖先通常以较少的双键异构化和较少的环化步骤催化更简单的反应。总体，