Molecular evolution of the substrate specificity of ent-kaurene synthases to adapt to gibberellin biosynthesis in land plants
Molecular evolution of the substrate specificity of ent-kaurene synthases to adapt to gibberellin biosynthesis in land plants
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DOI：
10.1042/bj20140134
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发表时间：
2014-09-15
影响因子：
4.1
通讯作者：
Kawaide, Hiroshi
中科院分区：
文献类型：
--
作者：
Shimane, Manami;Ueno, Yohei;Kawaide, Hiroshi
对位高岭烯是植物激素赤霉素生物合成的关键中间体。在开花植物的Ent-Kaurene生物合成中，两种二萜环化酶(DTC)--Ent-CDP合成酶(Et-CDP)和Ent-Kaurene合成酶(KS)分别催化香叶基香叶基二磷酸合成Ent-CDP和Ent-CDP合成Ent-Kaurene。与之相反，苔藓Physcomitrella patens有一个双功能的ENT-CPS/KS(PPCPs/KS)，可以催化两种环化反应。为了更深入地了解陆地植物中对位高岭烯生物合成酶的功能多样性，我们重点研究了石蒜卷柏中的DTC。本文描述了两种莫氏链球菌DTC(SmKS和SmDTC3)的体外特性。SmDTC3可将Et-CDP转化为Et-16和α-羟基龙烷，也可使用其他CDP立体异构体作为底物。值得注意的是，由Et-CDP合成Et-Kaurene的SmKS表现出相似的底物选择性：SmKS和SmDTC3都是以正常CDP为原料合成沙海松烯。因此，我们研究了不同植物KSS之间底物识别的差异。PPCPS/KS可以使用正常CDP、syn-CDP和Ent-CDP作为底物。相反，生菜KS对Et-CDP表现出高度的特异性，而水稻KS只识别Et-CDP。我们的研究表明，具有低底物专一性的古代KS已经进化为Ent-CDP对赤霉素生物合成的专一性。
ent-Kaurene is a key intermediate in the biosynthesis of the plant hormone gibberellin. In ent-kaurene biosynthesis in flowering plants, two diterpene cyclases (DTCs), ent-copalyl diphosphate (ent-CDP) synthase (ent-CPS) and ent-kaurene synthase (KS), catalyse the cyclization of geranylgeranyl diphosphate to ent-CDP and ent-CDP to ent-kaurene, respectively. In contrast, the moss Physcomitrella patens has a bifunctional ent-CPS/KS (PpCPS/KS) that catalyses both cyclization reactions. To gain more insight into the functional diversity of ent-kaurene biosynthetic enzymes in land plants, we focused on DTCs in the lycophyte Selaginella moellendorffii. The present paper describes the characterization of two S. moellendorffii DTCs (SmKS and SmDTC3) in vitro. SmDTC3 converted ent-CDP into ent-16 & ALPHA;-hydroxykaurane and also used other CDP stereoisomers as substrate. Remarkably, SmKS, which produces ent-kaurene from ent-CDP, showed similar substrate selectivity: both SmKS and SmDTC3 synthesized sandaracopimaradiene from normal CDP. Therefore, the diversity of substrate recognition among KSs from other plants was investigated. PpCPS/KS could use normal CDP and syn-CDP as well as ent-CDP as substrate. In contrast, lettuce KS showed high specificity for ent-CDP, and rice KS recognized only ent-CDP. Our studies imply that ancient KS having low substrate specificity has evolved to be specific for ent-CDP to the biosynthesis of gibberellin.