Functional Diversification of Kaurene Synthase-Like Genes in <i>Isodon rubescens</i>
作者:Baolong Jin、Guanghong Cui、Juan Guo、Jinfu Tang、Lixin Duan、Huixin Lin、Ye Shen、Tong Chen、Huabei Zhang、Luqi Huang
DOI:10.1104/pp.17.00202
日期:2017.6
Ent-kaurene diterpenoids are the largest group of known Isodon diterpenoids. Among them, oridonin is accumulated in the leaves, and is the most frequently studied compound because of its antitumor and antibacterial activities. We have identified five copalyl diphosphate synthase (CPS) and six kaurene synthase-like (KSL) genes by transcriptome profiling of Isodon rubescens leaves. An in vitro assay assigns ten of them to five different diterpene biosynthesis pathways, except IrCPS3 that has a mutation in the catalytic motif. The Lamiaceae-specific clade genes (IrCPS1 and IrCPS2) synthesize the intermediate copalyl diphosphate (normal-CPP), while IrCPS4 and IrCPS5 synthesize the intermediate ent-copalyl diphosphate (ent-CPP). IrKSL2, IrKSL4, and IrKSL5 react with ent-CPP to produce an ent-isopimaradiene-like compound, ent-atiserene and ent-kaurene, respectively. Correspondingly, the Lamiaceae-specific clade genes IrKSL1 or IrKSL3 combined with normal-CPP led to the formation of miltiradiene. The compound then underwent aromatization and oxidization with a cytochrome P450 forming two related compounds, abietatriene and ferruginol, which were detected in the root bark. IrKSL6 reacts with normal-CPP to produce isopimaradiene. IrKSL3 and IrKSL6 have the γβα tridomain structure, as these proteins tend to possess the bidomain structure of IrKSL1, highlighting the evolutionary history of KSL gene domain loss and further elucidating chemical diversity evolution from a macroevolutionary stance in Lamiaceae.
Ent-kaurene 二萜是已知的 Isodon 二萜中最大的一类。其中,Oridonin 在叶片中积累,是研究最多的化合物,因为它具有抗肿瘤和抗菌活性。我们通过对 Isodon rubescens 叶片进行转录组分析,确定了五个共醛基二磷酸合酶(CPS)和六个类高丽烯合酶(KSL)基因。通过体外检测,除 IrCPS3 的催化基团发生突变外,其余 10 个基因被归入 5 种不同的二萜生物合成途径。Lamiaceae 特有的支系基因(IrCPS1 和 IrCPS2)合成中间体 copalyl diphosphate(normal-CPP),而 IrCPS4 和 IrCPS5 则合成中间体 ent-copalyl diphosphate(ent-CPP)。IrKSL2、IrKSL4 和 IrKSL5 与 ent-CPP 反应,分别生成ent-isopimaradiene-like 化合物、ent-atiserene 和 ent-kaurene。与此对应,Lamiaceae 特有的支系基因 IrKSL1 或 IrKSL3 与正常-CPP 结合会生成 miltiradiene。然后,该化合物发生芳香化反应,并与细胞色素 P450 氧化,形成两种相关化合物,即根皮中检测到的阿维他三烯和铁杉醇。IrKSL6 与正常-CPP 反应生成异戊二烯。IrKSL3和IrKSL6具有γβα三叉域结构,而这些蛋白往往具有IrKSL1的双叉域结构,这突显了KSL基因域缺失的进化历史,并从宏观进化的角度进一步阐明了灯心草科植物化学多样性的进化。