Glandular trichomes produce a wide variety of secondary metabolites that are considered as major defensive chemicals against herbivore attack.The morphology and secondary metabolites of the peltate glandular trichomes...Glandular trichomes produce a wide variety of secondary metabolites that are considered as major defensive chemicals against herbivore attack.The morphology and secondary metabolites of the peltate glandular trichomes of a lianoid Labiatae,Colquhounia seguinii Vaniot,were investigated.Three new clerodane diterpenoids,seguiniilactones A-C（1-3）,were identified through precise trichome collection with laser microdissection,metabolic analysis with ultra performance liquid chromatography-tandem mass spectrometer,target compound isolation with classical phytochemical techniques,structure elucidation with spectroscopic methods.All compounds showed significant antifeedant activity against a generalist plant-feeding insect Spodoptera exigua.Seguiniilactone A（1） was approximately 17-fold more potent than the commercial neem oil.a-Substituted α,β-unsaturated γ-lactone functionality was found to be crucial for strong antifeedant activity of this class of compounds.Quantitative results indicated that the levels of these compounds in the peltate glandular trichomes and leaves were sufficiently high to deter the feeding by generalist insects.Moderate antifungal activity was observed for seguiniilactone C（3） against six predominant fungal species isolated from the diseased leaves of C seguinii,while seguiniilactones A and B were generally inactive.These findings suggested that seguiniilactones A-C might be specialized secondary metabolites in peltate glandular trichomes for the plant defense against insect herbivores and pathogens.展开更多
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 diphosphat...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.展开更多
基金supported financially by the NSFC-Yunnan Joint Fund(U1202263)the National Basic Research Program of China(973 Program) on Biological Control of Key Crop Pathogenic Nematodes(2013CB127505)+1 种基金the National Natural Science Foundation of China(31070320,31470395 and 31100222)the "Hundred Talents Program" of the Chinese Academy of Sciences(awarded to SH Li)
文摘Glandular trichomes produce a wide variety of secondary metabolites that are considered as major defensive chemicals against herbivore attack.The morphology and secondary metabolites of the peltate glandular trichomes of a lianoid Labiatae,Colquhounia seguinii Vaniot,were investigated.Three new clerodane diterpenoids,seguiniilactones A-C（1-3）,were identified through precise trichome collection with laser microdissection,metabolic analysis with ultra performance liquid chromatography-tandem mass spectrometer,target compound isolation with classical phytochemical techniques,structure elucidation with spectroscopic methods.All compounds showed significant antifeedant activity against a generalist plant-feeding insect Spodoptera exigua.Seguiniilactone A（1） was approximately 17-fold more potent than the commercial neem oil.a-Substituted α,β-unsaturated γ-lactone functionality was found to be crucial for strong antifeedant activity of this class of compounds.Quantitative results indicated that the levels of these compounds in the peltate glandular trichomes and leaves were sufficiently high to deter the feeding by generalist insects.Moderate antifungal activity was observed for seguiniilactone C（3） against six predominant fungal species isolated from the diseased leaves of C seguinii,while seguiniilactones A and B were generally inactive.These findings suggested that seguiniilactones A-C might be specialized secondary metabolites in peltate glandular trichomes for the plant defense against insect herbivores and pathogens.
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)+1 种基金the Science Foundation of Yunnan(2018FA017)the Youth Innovation Promotion association and“Western Light”Program of the CAS(to Y.Liu).
文摘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.
