germacrene-d and methyl-jasmonate

Considerable difference in artemisinin and its direct precursors, artemisinic acid and dihydroartemisinic acid, was detected between two chemotypes within the species Artemisia annua (A. annua). These two chemotypes showed differential metabolic response to methyl jasmonate (MeJA) elicitation. Exogenous application of MeJA resulted in an accumulation of dihydroartemisinic acid and artemisinin in Type I plants. In Type II plants, however, artemisinic acid and artemisinin level decreased dramatically under MeJA elicitation. Squalene and other sesquiterpenes, (e.g., caryophyllene, germacrene D), were stimulated by MeJA in both chemotypes. The effect of MeJA elicitation was also studied at the transcription level. Real time RT-PCR analysis showed a coordinated activation of most artemisinin pathway genes by MeJA in Type I plants. The lack of change in cytochrome P450 reductase (CPR) transcript in Type I plants indicates that the rate-limiting enzymes in artemisinin biosynthesis have yet to be identified. Other chemotype-specific electron donor proteins likely exist in A. annua to meet the demand for P450-mediated reactions in MeJA-mediated cellular processes. In Type II plants, mRNA expression patterns of most pathway genes were consistent with the reduced artemisinin level. Intriguingly, the mRNA transcript of aldehyde dehydrogenase1 (ADHL1), an enzyme which catalyzes the oxidation of artemisinic and dihydroartemisinic aldehydes, was upregulated by MeJA. The differential metabolic response to MeJA suggests a chemotype-dependent metabolic flux control towards artemisinin and sterol production in the species A. annua.

Topics: Acetates; Aldehyde Dehydrogenase 1 Family; Alkyl and Aryl Transferases; Artemisia annua; Artemisinins; Cyclopentanes; Cytochrome P-450 Enzyme System; Gas Chromatography-Mass Spectrometry; Gene Expression Regulation, Plant; Isoenzymes; NADPH-Ferrihemoprotein Reductase; Oxidoreductases; Oxylipins; Plant Growth Regulators; Plant Leaves; Plant Proteins; Polycyclic Sesquiterpenes; Retinal Dehydrogenase; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Sesquiterpenes; Sesquiterpenes, Germacrane; Squalene; 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