摘要
Terpenoids are the largest class of natural products with complex structures and extensive bioactivities;their scaffolds are generated by diverse terpenoid synthases(TPSs)from a limited number of isoprenoid diphosphate precursors.Promiscuous TPSs play important roles in the evolution of terpenoid chemodiversity,but they remain largely unappreciated.Here,an extremely promiscuous terpenoid synthase(CcTPS1)of the TPS-b subfamily was cloned and functionally characterized from a leaf-specific transcriptome of the Lamiaceae plant Colquhounia coccinea var.mollis.CcTPS1 is the first sester-/di-/sesqui-/mono-TPS identified from the plant kingdom,accepting C_(25)/C_(20)/C_(15)/C_(10) diphosphate substrates to generate a panel of sester-/di-/sesqui-/mono-terpenoids.Engineered Escherichia coli expressing CcTPS1 produced three previously unreported terpenoids(two sesterterpenoids and a diterpenoid)with rare cyclohexanecontaining skeletons,along with four sesquiterpenoids and one monoterpenoid.Their structures were elucidated by extensive nuclear magnetic resonance spectroscopy.Nicotiana benthamiana transiently expressing CcTPS1 also produced the diterpenoid and sesquiterpenoids,demonstrating the enzyme’s promiscuity in planta.Its highly leaf-specific expression pattern combined with detectable terpenoid products in leaves of C.coccinea var.mollis and N.benthamiana expressing CcTPS1 suggested that CcTPS1 was mainly responsible for diterpenoid and sesquiterpenoid biosynthesis in plants.CcTPS1 expression and the terpenoid products could be induced by methyl jasmonate,suggesting their possible role in plant–environment interaction.CcTPS1 was localized to the cytosol and may differ from mono-TPSs in subcellular compartmentalization and substrate tolerance.These findings will greatly aid our understanding of plant TPS evolution and terpenoid chemodiversity;they also highlight the enormous potential of transcriptome mining and heterologous expression for the exploration of unique enzymes and natural products hidden in plants.
基金
supported financially by the National Natural Science Foundation of China(21937006,31770390,31770340 and 31525005)
the Yunnan Key Research and Development Program(no.2019ZF011-2)
the Science Foundation of Yunnan(2018FA017)
the Youth Innovation Promotion association and“Western Light”Program of the CAS(to Y.Liu).
