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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Functional plasticity of paralogous diterpene synthases involved in conifer defense
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Functional plasticity of paralogous diterpene synthases involved in conifer defense

机译：针叶树防御中涉及的同源二萜合酶的功能可塑性

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The diversity of terpenoid compounds produced by plants plays an important role in mediating various plant-herbivore, plant-pollinator, and plant-pathogen interactions. This diversity has resulted from gene duplication and neofunctionalization of the enzymes that synthesize and subsequently modify terpenes. Two diterpene synthases in Norway spruce (Picea abies), isopimara-diene synthase and levopimaradiene/abietadiene synthase, provide the hydrocarbon precursors for most of the diterpene resin acids found in the defensive oleoresin of conifers. Although these paralogous enzymes are 91 % identical at the amino acid level, one is a single-product enzyme, whereas the other is a multiproduct enzyme that forms completely different products. We used a rational approach of homology modeling, protein sequence comparison, domain swapping, and a series of reciprocal site-directed mutagenesis to identify the specific residues that direct the different product outcomes. A one-amino acid mutation switched the levopimaradiene/abietadiene synthase into producing isopimara-diene and sandaracopimaradiene and none of its normal products. Four mutations were sufficient to reciprocally reverse the product profiles for both of these paralogous enzymes while maintaining catalytic efficiencies similar to the wild-type enzymes. This study illustrates how neofunctionalization can result from relatively minor changes in protein sequence, increasing the diversity of secondary metabolites important for conifer defense.
机译：植物产生的萜类化合物的多样性在介导各种植物-草食动物，植物传粉媒介和植物-病原体相互作用中起重要作用。这种多样性是由基因复制和合成并随后修饰萜烯的酶的新功能化引起的。挪威云杉（Picea abies）中的两种二萜合酶，即异欧美拉二烯合酶和左旋丙二烯/松香二烯合酶，​​为针叶树防御性油树脂中发现的大多数二萜树脂酸提供了烃前体。尽管这些旁系酶在氨基酸水平上具有91％的同一性，但一种是单产物酶，而另一种是形成完全不同产物的多产物酶。我们使用了一种合理的同源性建模，蛋白质序列比较，结构域交换以及一系列相互的定点诱变方法，以鉴定出指导不同产品结果的特定残基。一个氨基酸突变将左旋海马/松香二烯合酶转变为产生异海马-二烯和三水蛇麻草和其正常产物。四个突变足以相互逆转这两个旁系酶的产物谱，同时保持类似于野生型酶的催化效率。这项研究说明了蛋白质功能相对较小的变化如何导致新功能化，从而增加了对针叶树防御至关重要的次生代谢产物的多样性。

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