Farnesene Isomers Research Articles

Can a Mixture of Farnesene Isomers Avert the Infestation of Aphids in Sugar Beet Crops?

The negative impact of pesticides on the environment and the potential of pest species to develop pesticide resistance make it necessary to explore new methods of pest control. Pheromones and other behavior-modifying semiochemicals are already important in integrated pest management (IPM). (E)-ß-farnesene (EBF) is a semiochemical that acts as an alarm pheromone in aphids. Upon perception of EBF, aphids stop feeding, move away, and sometimes even abandon the host plant. The aphids Myzus persicae and Aphis fabae are significant crop pests and vectors of many harmful phytopathogens affecting sugar beet (Beta vulgaris). Field trials were conducted at different locations in Germany to test whether dispensers containing a mixture of farnesene isomers (FIMs) including EBF were able to reduce the infestation of these species on sugar beet. Our results showed a reduction in aphid abundance in the FIM-treated patches in two out of three sites. Therefore, we hypothesize that FIM dispensers could prevent aphid infestation and could be used in combination with other IPM measures. However, more research is required to increase the effect and ensure the reliability of this method.

Secondary Organic Aerosol Formation from Healthy and Aphid-Stressed Scots Pine Emissions.

One barrier to predicting biogenic secondary organic aerosol (SOA) formation in a changing climate can be attributed to the complex nature of plant volatile emissions. Plant volatile emissions are dynamic over space and time, and change in response to environmental stressors. This study investigated SOA production from emissions of healthy and aphid-stressed Scots pine saplings via dark ozonolysis and photooxidation chemistry. Laboratory experiments using a batch reaction chamber were used to investigate SOA production from different plant volatile mixtures. The volatile mixture from healthy plants included monoterpenes, aromatics, and a small amount of sesquiterpenes. The biggest change in the volatile mixture for aphid-stressed plants was a large increase (from 1.4 to 7.9 ppb) in sesquiterpenes—particularly acyclic sesquiterpenes, such as the farnesene isomers. Acyclic sesquiterpenes had different effects on SOA production depending on the chemical mechanism. Farnesenes suppressed SOA formation from ozonolysis with a 9.7–14.6% SOA mass yield from healthy plant emissions and a 6.9–10.4% SOA mass yield from aphid-stressed plant emissions. Ozonolysis of volatile mixtures containing more farnesenes promoted fragmentation reactions, which produced higher volatility oxidation products. In contrast, plant volatile mixtures containing more farnesenes did not appreciably change SOA production from photooxidation. SOA mass yields ranged from 10.8 to 23.2% from healthy plant emissions and 17.8–26.8% for aphid-stressed plant emissions. This study highlights the potential importance of acyclic terpene chemistry in a future climate regime with an increased presence of plant stress volatiles.

An odorant receptor and glomerulus responding to farnesene in Helicoverpa assulta (Lepidoptera: Noctuidae)

Terpenoids emitted from herbivore-damaged plants were found to play an important role in regulating tritrophic interactions. How herbivores and their natural enemies perceive terpenoids has not been thoroughly elucidated to date. Using in vivo calcium imaging, we found in this study that farnesene activates one glomerulus in the antennal lobe of female Helicoverpa assulta. The response induced by a mixture of farnesene isomers is stronger than that elicited by E-β-farnesene alone. In the Xenopus oocyte expression system, HassOR23/ORco is narrowly tuned to farnesene isomers and compounds with similar structures. Finally, the behavioral studies showed that the farnesene isomers have an inhibitory effect on oviposition of female H. assulta, but have an attractive effect on host searching of Campoletis chlorideae, the key endoparasitoid of H. assulta larvae. These results demonstrate that farnesene isomers are encoded by a labeled-line mode in the olfactory system of female H. assulta, suggesting that farnesene as a chemical signal from plants has important behavioral relevance and evolutionary implications in the tritrophic context.

Neuroprotective effects of farnesene against hydrogen peroxide-induced neurotoxicity in vitro.

Oxidative stress is highly damaging to cellular macromolecules and is also considered a main cause of the loss and impairment of neurons in several neurodegenerative disorders. Recent reports indicate that farnesene (FNS), an acyclic sesquiterpene, has antioxidant properties. However, little is known about the effects of FNS on oxidative stress-induced neurotoxicity. We used hydrogen peroxide (H2O2) exposure for 6h to model oxidative stress. Therefore, this experimental design allowed us to explore the neuroprotective potential of different FNS isomers (α-FNS and β-FNS) and their mixture (Mix-FNS) in H2O2-induced toxicity in newborn rat cerebral cortex cell cultures for the first time. For this aim, both MTT and lactate dehydrogenase assays were carried out to evaluate cell viability. Total antioxidant capacity (TAC) and total oxidative stress (TOS) parameters were used to assess oxidative alterations. In addition to determining of 8-hydroxy-2-deoxyguanosine (8-OH-dG) levels in vitro, the comet assay was also performed for measuring the resistance of neuronal DNA to H2O2-induced challenge. Our results showed that survival and TAC levels of the cells decreased, while TOS, 8-OH-dG levels and the mean values of the total scores of cells showing DNA damage (comet assay) increased in the group treated with H2O2 alone. But pretreatment of FNS suppressed the cytotoxicity, genotoxicity and oxidative stress, which were increased by H2O2 in clear type of isomers and applied concentration-dependent manners. The order of antioxidant effectiveness for modulating H2O2-induced oxidative stress-based neurotoxicity and genotoxicity is as β-FNS>Mix-FNS>α-FNS.

Characterisation of pear distillates from wild and cultivated varieties in Sardinia

SummaryThe aroma fraction of Italian distillates of wild (Pyrus amygidaliformis, Vill., namely ‘Pirastru’) and cultivated (Pyrus communis, L. cvs. ‘Coscia’, ‘Precoce di Fiorano’ and ‘Butirru de Austu’) pear varieties grown in the northern part of the island of Sardinia was investigated. Distillates from fermented mashes were obtained from the same producer and, in most cases, for 3 years following the same production process. Aroma analyses were performed by GC‐FID and GC‐MS techniques with direct GC injection of full proof distillates. Differences were found in the aromatic profile of all the distillates depending on their varietal origin. Wild Pirastru pear distillates were the richest in isoeugenol (0.186 g hL−1 a.a.), ethyl benzoate (0.388 g hL−1 a.a.) and ethyl phenylacetate (0.12 g hL−1 a.a.) but the poorest in 1‐hexanol (2.69 g hL−1 a.a.), n‐hexyl acetate (0.07 g hL−1 a.a.), Σ‐farnesene isomers (0.80 g hL−1 a.a.) and citronellol (0.007 g hL−1 a.a.). Pirastru distillates were also the poorest in methyl and ethyl unsaturated decanoate isomers, the so‐called Williams pear esters (0.002 g hL−1 a.a.). On the contrary, these compounds that characterise the aroma of Williams pear distillates were abundant in Coscia spirits (1.032 g hL−1 a.a.). The latter, together with Precoce di Fiorano, were rich in farnesene isomers (6.48 and 9.26 g hL−1 a.a. respectively). Evaluation of the data by univariate (anova and Kruskal–Wallis) and multivariate (PCA and HCA) statistical analyses revealed that some components (the classes of acetates, farnesene isomers, methyl and ethyl unsaturated decanoate esters and citronellol) are relevant in discriminating the distillates according to variety.

Investigating conservation of the albaflavenone biosynthetic pathway and CYP170 bifunctionality in streptomycetes

Albaflavenone, a tricyclic sesquiterpene antibiotic, is biosynthesized in Streptomyces coelicolor A3(2) by enzymes encoded in a two-gene operon. Initially, sesquiterpene cyclase catalyzes the cyclization of farnesyl diphosphate to the terpenoid epi-isozizaene, which is oxidized to the final albaflavenone by cytochrome P450 (CYP)170A1. Additionally, this CYP is a bifunctional enzyme, being able to also generate farnesene isomers from farnesyl diphosphate, owing to a terpene synthase active site moonlighting on the CYP molecule. To explore the functionality of this operon in other streptomycetes, we have examined culture extracts by GC/MS and established the presence of albaflavenone in five Streptomyces species. Bioinformatics examination of the predicted CYP170 primary amino acid sequences revealed substitutions in the CYP terpene synthase active site. To examine whether the terpene synthase site was catalytically active in another CYP170, we characterized the least related CYP170 orthologue from Streptomyces albus (CYP170B1). Following expression and purification, CYP170B1 showed a normal reduced CO difference spectrum at 450 nm, in contrast to the unusual 440-nm peak observed for S. coelicolor A3(2) CYP170A1. CYP170B1 can catalyze the conversion of epi-isozizaene to albaflavenone, but was unable to catalyze the conversion of farnesyl diphosphate to farnesene. Molecular modeling with our crystal structure of CYP170A1 suggests that the absence of key amino acids for binding the essential terpene synthase cofactor Mg(2+) may be the explanation for the loss of CYP170B1 bifunctionality.

Biomedically important pathogenic fungi detection with volatile biomarkers

Volatile chemical profiles collected from the headspace of Aspergillus fumigatus (a pathogenic fungus that causes invasive pulmonary aspergillosis, allergic bronchopulmonary aspergillosis and chronic fungal sinusitis) grown on media with the connective tissue protein elastin, found in lung tissue, contained a large abundance of the sesquiterpene farnesene (3,7,11-trimethyl-1,3,6,10-dodecatetraene) and, depending on extraction time and sorbent material, other farnesene isomers and sesquiterpenes such as bisabolene (methyl-4-(6-methylhepta-1,5-dien-2-yl)cyclohex-1-ene). When human lung cells were cultured externally and infected with A. fumigatus, farnesene was also detected in each model lung system. Volatiles measured from cultured nasal lavage collected from a patient diagnosed with chronic fungal sinusitis, a condition frequently caused by A. fumigatus, revealed the presence of another pathogenic fungus, less frequently responsible for sinusitis, Epicoccum nigrum. The volatile profile of E. nigrum differed markedly from that of A. fumigatus with no sesquiterpenes detected.

Sandalwood Fragrance Biosynthesis Involves Sesquiterpene Synthases of Both the Terpene Synthase (TPS)-a and TPS-b Subfamilies, including Santalene Synthases

Sandalwood oil is one of the worlds most highly prized fragrances. To identify the genes and encoded enzymes responsible for santalene biosynthesis, we cloned and characterized three orthologous terpene synthase (TPS) genes SaSSy, SauSSy, and SspiSSy from three divergent sandalwood species; Santalum album, S. austrocaledonicum, and S. spicatum, respectively. The encoded enzymes catalyze the formation of α-, β-, epi-β-santalene, and α-exo-bergamotene from (E,E)-farnesyl diphosphate (E,E-FPP). Recombinant SaSSy was additionally tested with (Z,Z)-farnesyl diphosphate (Z,Z-FPP) and remarkably, found to produce a mixture of α-endo-bergamotene, α-santalene, (Z)-β-farnesene, epi-β-santalene, and β-santalene. Additional cDNAs that encode bisabolene/bisabolol synthases were also cloned and functionally characterized from these three species. Both the santalene synthases and the bisabolene/bisabolol synthases reside in the TPS-b phylogenetic clade, which is more commonly associated with angiosperm monoterpene synthases. An orthologous set of TPS-a synthases responsible for formation of macrocyclic and bicyclic sesquiterpenes were characterized. Strict functionality and limited sequence divergence in the santalene and bisabolene synthases are in contrast to the TPS-a synthases, suggesting these compounds have played a significant role in the evolution of the Santalum genus.

Crystal Structure of Albaflavenone Monooxygenase Containing a Moonlighting Terpene Synthase Active Site

Albaflavenone synthase (CYP170A1) is a monooxygenase catalyzing the final two steps in the biosynthesis of this antibiotic in the soil bacterium, Streptomyces coelicolor A3(2). Interestingly, CYP170A1 shows no stereo selection forming equal amounts of two albaflavenol epimers, each of which is oxidized in turn to albaflavenone. To explore the structural basis of the reaction mechanism, we have studied the crystal structures of both ligand-free CYP170A1 (2.6 A) and complex of endogenous substrate (epi-isozizaene) with CYP170A1 (3.3 A). The structure of the complex suggests that the proximal epi-isozizaene molecules may bind to the heme iron in two orientations. In addition, much to our surprise, we have found that albaflavenone synthase also has a second, completely distinct catalytic activity corresponding to the synthesis of farnesene isomers from farnesyl diphosphate. Within the cytochrome P450 alpha-helical domain both the primary sequence and x-ray structure indicate the presence of a novel terpene synthase active site that is moonlighting on the P450 structure. This includes signature sequences for divalent cation binding and an alpha-helical barrel. This barrel is unusual because it consists of only four helices rather than six found in all other terpene synthases. Mutagenesis establishes that this barrel is essential for the terpene synthase activity of CYP170A1 but not for the monooxygenase activity. This is the first bifunctional P450 discovered to have another active site moonlighting on it and the first time a terpene synthase active site is found moonlighting on another protein.

SECRETION OF VENOM AND DUFOUR GLANDS IN THE ANT Leptogenys diminuta

The venom glands of both workers and ergatoid queens of the ant Leptogenys diminuta contain 4–methyl-3–heptanol and a mixture of esters of this alcohol and long-chain fatty acids. Only the higher proportion of 4–methyl-3–heptanone in the queens represents a chemical difference between the castes. The Dufour gland secretion of workers and queens, however, shows considerable differences. Both share a series of long-chain hydrocarbons with 9and 7–pentacosene as the major substances of the secretion but are otherwise differentiated by the presence in the workers only of three farnesene isomers, whereas queens contain a wide range of substances. The mated queen had a very complex mixture of hydrocarbons, esters and terpenes. These substances were also present in the virgin females but in smaller quantities.

Urine marking in male mice: responses to natural and synthetic chemosignals.

The effects of natural chemosignals and their synthetic terpenic analogs on urinary marking in mice were investigated. The number and size of marking spots, and percentage of response and avoidance/counter-marking behavior, were measured for dominant and subordinate males. The males' marking behavior was found to differ significantly based on the type of stimulus sample used. Marking behavior in response to female urine was significantly altered by addition of synthetic analogs (farnesene isomers) to it. Both dominant and subordinate males avoided marking the section of the test area soiled with stimulus samples containing either natural or synthetic farnesenes. Differential responses of the dominant and subordinate male mice were observed.

Chemotaxonomic study of undescribed species ofMyrmica ant from Idaho

An undescribed species ofMyrmica collected in Idaho has been shown to have the same substances in its mandibular glands (3-octanol and 3-octanone and related 3-alkanols and 3-alkanones) and in its Dufour gland (linear alkanes, alkenes, and farnesene isomers and homologs) as previously examined European species ofMyrmica. The poison gland contains the trail pheromone 3-ethyl-2,5-dimethylpyrazine, common to allMyrmica species studied so far. The Dufour gland contains large amounts of bishomofarnesene, which easily distinguishes it from some 13 otherMyrmica already known.

Species-specific secretions of the dufour glands of three species of formicine ants (Hymenoptera: Formicidae)

The Dufour glands of F. selysi and C. lateralis have been examined for the first time, and those of F. rufibarbis are re-examined. The secretion of F. selysi is similar to (but distinguishable from) that of F lemani, with chiefly undecane and smaller amounts of other linear and some branched hydrocarbons. The gland of F rufibarbis contains hydrocarbons, esters, alcohols and lactones, with decyl acetate the major substance followed by undecane. Three alkyl formates have also been identified in the mixture. No farnesene isomers or homologues were detected. C. lateralis also belongs to tne group of formicine ants that produces a mixture of hydrocarbons and related oxygenated compounds. Its major components are tridecane followed by tetradecyl acetate but for some individuals 99% of the secretion consisted of tridecane and 5-pentadecane only. The composition of the single queen's gland was not different. Each of these species produces a blend of substances not found in any otherspecies yet examined. All three have relatively large glands with more than 1 μg secretion, on average. The heads and dissected mandibular glands were also examined but no quantity of material was found that indicated the mandibular glands contained volatile pheromones.