Evolution of Conifer Diterpene Synthases: Diterpene Resin Acid Biosynthesis in Lodgepole Pine and Jack Pine Involves Monofunctional and Bifunctional Diterpene Synthases
Evolution of Conifer Diterpene Synthases: Diterpene Resin Acid Biosynthesis in Lodgepole Pine and Jack Pine Involves Monofunctional and Bifunctional Diterpene Synthases
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DOI：
10.1104/pp.112.208546
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发表时间：
2013-02-01
期刊：
影响因子：
7.4
通讯作者：
Bohlmann, Joerg
中科院分区：
文献类型：
--
作者：
Hall, Dawn E.;Zerbe, Philipp;Bohlmann, Joerg
二萜树脂酸（DRAs）是松树（Pinus spp.）油树脂的主要成分。它们在针叶树抵御昆虫和病原体以及作为工业生物产品的可再生资源方面发挥着关键作用。DRAs的核心结构是在二萜合成酶（ditps）使香叶基香叶基二磷酸（GGPP）环异构化的次生（即特化）代谢过程中形成的。先前描述的裸子植物DRA生物合成的ditps是双功能酶，它催化GGPP的初始双环化，然后在两个离散的II类和I类活性位点上重排(+)-共聚二磷酸中间体。相比之下，赤霉素初级（即一般）代谢的类似二萜是由两个单功能II类和I类ditps的连续活性产生的。通过高通量转录组测序，我们从短叶松（Pinus banksiana）和黑松（Pinus contorta）中发现了11个diTPS。其中三个与已知的针叶树双功能左旋己二烯/二烯合成酶同源。令人惊讶的是，两组同源的pbditps和pcditps都是单功能I类酶，缺乏功能II类活性位点，并将(+)-共丙二磷酸转化为异马二烯和匹马二烯，而不是GGPP。黑松和短叶松的二萜谱和转录组序列与这些ditps在DRA生物合成中的作用一致。DRA生物合成的单功能I类diTPS是裸子植物特异性TPS-d3亚家族中的一个新分支，它是从双功能diTPS而不是赤霉素代谢的单功能酶（TPS-c和TPS-e）进化而来的。同源性模型表明，I类活性位点的改变可能导致了它们相对于其他针叶树ditps的功能特化。
Diterpene resin acids (DRAs) are major components of pine (Pinus spp.) oleoresin. They play critical roles in conifer defense against insects and pathogens and as a renewable resource for industrial bioproducts. The core structures of DRAs are formed in secondary (i.e. specialized) metabolism via cycloisomerization of geranylgeranyl diphosphate (GGPP) by diterpene synthases (diTPSs). Previously described gymnosperm diTPSs of DRA biosynthesis are bifunctional enzymes that catalyze the initial bicyclization of GGPP followed by rearrangement of a (+)-copalyl diphosphate intermediate at two discrete class II and class I active sites. In contrast, similar diterpenes of gibberellin primary (i.e. general) metabolism are produced by the consecutive activity of two monofunctional class II and class I diTPSs. Using high-throughput transcriptome sequencing, we discovered 11 diTPS from jack pine (Pinus banksiana) and lodgepole pine (Pinus contorta). Three of these were orthologous to known conifer bifunctional levopimaradiene/abietadiene synthases. Surprisingly, two sets of orthologous PbdiTPSs and PcdiTPSs were monofunctional class I enzymes that lacked functional class II active sites and converted (+)-copalyl diphosphate, but not GGPP, into isopimaradiene and pimaradiene as major products. Diterpene profiles and transcriptome sequences of lodgepole pine and jack pine are consistent with roles for these diTPSs in DRA biosynthesis. The monofunctional class I diTPSs of DRA biosynthesis form a new clade within the gymnosperm-specific TPS-d3 subfamily that evolved from bifunctional diTPS rather than monofunctional enzymes (TPS-c and TPS-e) of gibberellin metabolism. Homology modeling suggested alterations in the class I active site that may have contributed to their functional specialization relative to other conifer diTPSs.