humulene and methyl-jasmonate

The resinous portions of Aquilaria and Gyrinops plants are known as 'agarwood' and have a distinctive fragrance. To examine the biosynthesis of these fragrant compounds, we previously established cell cultures of Aquilaria crassna in which the production of three sesquiterpenes (α-guaiene, α-humulene, and δ-guaiene) could be induced by methyl jasmonate (MJ), and showed that cloned δ-guaiene synthase from MJ-treated cells is involved in the synthesis of these three compounds, although only very small amounts of α-humulene are produced. In the present study, cDNAs encoding α-humulene synthases were also isolated. Three putative sesquiterpene synthase clones (AcHS1-3) isolated from the MJ-treated cells had very similar amino acid sequences and shared 52 % identity with δ-guaiene synthases. The recombinant enzymes catalyzed the formation of α-humulene as a major product. Expression of transcripts of the α-humulene synthase and δ-guaiene synthase genes in cultured cells increased after treatment with MJ. These results revealed that these α-humulene and δ-guaiene synthases are involved in the synthesis of three sesquiterpenes induced by MJ treatment.

Topics: Acetates; Cell Culture Techniques; Cyclopentanes; Monocyclic Sesquiterpenes; Oxylipins; Sesquiterpenes; Thymelaeaceae

Cotton plants accumulate gossypol and related sesquiterpene aldehydes, which function as phytoalexins against pathogens and feeding deterrents to herbivorous insects. However, to date little is known about the biosynthesis of volatile terpenes in this crop. Herein is reported that 5 monoterpenes and 11 sesquiterpenes from extracts of a glanded cotton cultivar, Gossypium hirsutum cv. CCRI12, were detected by gas chromatography-mass spectrometry (GC-MS). By EST data mining combined with Rapid Amplification of cDNA Ends (RACE), full-length cDNAs of three terpene synthases (TPSs), GhTPS1, GhTPS2 and GhTPS3 were isolated. By in vitro assays of the recombinant proteins, it was found that GhTPS1 and GhTPS2 are sesquiterpene synthases: the former converted farnesyl pyrophosphate (FPP) into β-caryophyllene and α-humulene in a ratio of 2:1, whereas the latter produced several sesquiterpenes with guaia-1(10),11-diene as the major product. By contrast, GhTPS3 is a monoterpene synthase, which produced α-pinene, β-pinene, β-phellandrene and trace amounts of other monoterpenes from geranyl pyrophosphate (GPP). The TPS activities were also supported by Virus Induced Gene Silencing (VIGS) in the cotton plant. GhTPS1 and GhTPS3 were highly expressed in the cotton plant overall, whereas GhTPS2 was expressed only in leaves. When stimulated by mechanical wounding, Verticillium dahliae (Vde) elicitor or methyl jasmonate (MeJA), production of terpenes and expression of the corresponding synthase genes were induced. These data demonstrate that the three genes account for the biosynthesis of volatile terpenes of cotton, at least of this Upland cotton.

Topics: Acetates; Alkyl and Aryl Transferases; Bicyclic Monoterpenes; Bridged Bicyclo Compounds; Cyclohexane Monoterpenes; Cyclohexenes; Cyclopentanes; Gas Chromatography-Mass Spectrometry; Gossypium; Intramolecular Lyases; Monocyclic Sesquiterpenes; Monoterpenes; Oxylipins; Phytoalexins; Polycyclic Sesquiterpenes; Polyisoprenyl Phosphates; Sesquiterpenes; Sesquiterpenes, Guaiane; Terpenes; Volatile Organic Compounds

Cotton (Gossypium hirsutum L.) plants damaged by insects emit a blend of volatiles, including monoterpenes and sesquiterpenes, which can directly repel herbivores and/or indirectly protect the plant by attracting natural enemies of the herbivores. To understand the molecular basis of terpene biosynthesis and regulation in cotton, two terpene synthase genes, GhTPS1 and GhTPS2, were heterologously expressed and characterized. Recombinant GhTPS1 accepted farnesyl pyrophosphate as substrate and produced (E)-β-caryophyllene and α-humulene. GhTPS2 was characterized as a monoterpene synthase which formed α-pinene and β-pinene using geranyl pyrophosphate as substrate. Quantitative real-time PCR analysis revealed that GhTPS1 and GhTPS2 gene expression was elevated after methyl jasmonate (MeJA) treatment in cotton leaves. Moreover, feeding of the green plant bug Apolygus lucorum, a major cotton pest in northern China, resulted in increased GhTPS2 expression in young leaves, suggesting that GhTPS2 might be involved in plant defense in cotton.

Topics: Acetates; Adaptation, Physiological; Alkyl and Aryl Transferases; Animals; Bicyclic Monoterpenes; Bridged Bicyclo Compounds; Carbon-Oxygen Lyases; China; Cyclopentanes; Gene Expression; Genes, Plant; Gossypium; Herbivory; Insecta; Monocyclic Sesquiterpenes; Monoterpenes; Oxylipins; Plant Diseases; Plant Leaves; Plant Proteins; Polycyclic Sesquiterpenes; Polyisoprenyl Phosphates; Sesquiterpenes; Terpenes

The volatile constituents in the flowers of Aglaia odorata were extracted by supercritical CO2 fluid under 25 MPa and 40 degrees C for 80 min. The oil yield was 2.64%. These volatile constituents were separated and identified by capillary gas chromatography-mass spectrometry (GC-MS). Experiments were performed on an Agilent 6890 GC Chromatograph with Agilent 5973N Mass Selective Detector. The GC separation conditions was carried out on an HP-5MS capillary column (60 m x 250 microm, 0.25 microm); oven temperature, 50 degrees C (held for 2 min) to 280 degrees C at a rate of 5 degrees C/min, and held for 8 min; split ratio, 1 : 10; injector temperature, 270 degrees C. Mass spectra were collected in the scan range of m/z 50 - 550. The measurements were performed with electron bombardment ion (EI) source with electron energy of 70 eV and electron multiplier voltage of 1.65 kV. The results showed that 54 peaks were separated and 48 compounds were identified for the essential oil extracted from Aglaia odorata L. There were 18 terpenes, 12 esters and other constituents in the volatile oil fraction. The constituents in the oil fraction were alpha-humulene, followed by ethyl linolenate, germacrene D, beta-elemene, copaene, caryophyllene, methyl jasmonate, beta-humulene-7-ol, ethyl palmitate, etc.

Topics: Acetates; Aglaia; Cyclopentanes; Flowers; Gas Chromatography-Mass Spectrometry; Linolenic Acids; Monocyclic Sesquiterpenes; Oils, Volatile; Oxylipins; Palmitic Acids; Polycyclic Sesquiterpenes; Sesquiterpenes; Sesquiterpenes, Germacrane; Temperature