摘要
Terpenoids are the largest and most diverse class of plant-specialized metabolites, which function in diverse physiological processes during plant development. In the biosynthesis of plant terpenoids, short-chain prenyltransferases （SC-PTs）, together with terpene synthases （TPSs）, play critical roles in determining terpenoid diversity. SC-PTs biosynthesize prenyl pyrophosphates with different chain lengths, and these compounds are the direct precursors of terpenoids. Arabidopsis thaliana possesses a subgroup of SC-PTs whose functions are not clearly known. In this study, we focus on 10 geranylgeranyl pyro- phosphate synthase-like [GGPPSL] proteins, which are commonly thought to produce GGPP [C20]. We found that a subset of members of the Arabidopsis GGPPSL gene family have undergone neo- functionalization： GGPPSL6, 7, 9, and 10 mainly have geranylfarnesyl pyrophosphate synthase activity （C25; renamed AtGFPPS1, 2, 3, and 4）, and GGPPSL8 produces even longer chain prenyl pyrophosphate （〉C30; renamed polyprenyl pyrophosphate synthase 2, AtPPPS2）. By solving the crystal structures of AtGFPPS2, AtPPPS2, and AtGGPPS11, we reveal the product chain-length determination mechanism of SC-PTs and interpret it as a ＂three floors＂ model. Using this model, we identified a novel GFPPS clade distributed in Brassicaceae plants and found that the GFPPS gene typically occurs in tandem with a gene encoding a TPS, forming a GFPPS-TPS gene cluster.
Terpenoids are the largest and most diverse class of plant-specialized metabolites, which function in diverse physiological processes during plant development. In the biosynthesis of plant terpenoids, short-chain prenyltransferases （SC-PTs）, together with terpene synthases （TPSs）, play critical roles in determining terpenoid diversity. SC-PTs biosynthesize prenyl pyrophosphates with different chain lengths, and these compounds are the direct precursors of terpenoids. Arabidopsis thaliana possesses a subgroup of SC-PTs whose functions are not clearly known. In this study, we focus on 10 geranylgeranyl pyro- phosphate synthase-like [GGPPSL] proteins, which are commonly thought to produce GGPP [C20]. We found that a subset of members of the Arabidopsis GGPPSL gene family have undergone neo- functionalization： GGPPSL6, 7, 9, and 10 mainly have geranylfarnesyl pyrophosphate synthase activity （C25; renamed AtGFPPS1, 2, 3, and 4）, and GGPPSL8 produces even longer chain prenyl pyrophosphate （〉C30; renamed polyprenyl pyrophosphate synthase 2, AtPPPS2）. By solving the crystal structures of AtGFPPS2, AtPPPS2, and AtGGPPS11, we reveal the product chain-length determination mechanism of SC-PTs and interpret it as a ＂three floors＂ model. Using this model, we identified a novel GFPPS clade distributed in Brassicaceae plants and found that the GFPPS gene typically occurs in tandem with a gene encoding a TPS, forming a GFPPS-TPS gene cluster.
