Epicuticular Fatty Acids Research Articles

Shifts in carbon and nitrogen stable isotope composition and epicuticular lipids in leaves reflect early water-stress in vineyards

Changes in leaf carbon and nitrogen isotope composition (δ13C and δ15N values) and the accumulation of epicuticular lipids have been associated with plant responses to water stress. We investigated their potential use as indicators of early plant water deficit in two grapevine (Vitis vinifera L.) cultivars, Chasselas and Pinot noir, that were field-grown under well-watered and water-deficient conditions. We tested the hypothesis that the bulk δ13C and δ15N values and the concentrations of epicuticular fatty acids may change in leaves of similar age with the soil water availability. For this purpose, leaves were sampled at the same position in the canopy at different times (phenological stages) during the 2014 growing season. Bulk dry matter of young leaves from flowering to veraison had higher δ13C values, higher total nitrogen content, and lower δ15N values than old leaves. In both cultivars, δ15N values were strongly correlated with plant water deficiency, demonstrating their integration of the plant water stress response. δ13C values recorded the water deficiency only in those plants that had not received foliar organic fertilization. The soil water deficiency triggered the accumulation of C>26 fatty acids in the cuticular waxes. The compound-specific isotope analysis (CSIA) of fatty acids from old leaves showed an increase in δ13C among the C16-C22 chains, including stress signaling linoleic and linolenic acids. Our results provide evidence for leaf 13C-enrichment, 15N-depletion, and enhanced FA-chain elongation and epicuticular accumulation in the grapevine response to water stress. The leaf δ13C and δ15N values, and the concentration of epicuticular fatty acids can be used as reliable and sensitive indicators of plant water deficit even when the level of water stress is low to moderate. They could also be used, particularly the more cost-efficient δ13C and δ15N measurements, for periodic biogeochemical mapping of the plant water availability at the vineyard and regional scale.

Quantitative comparison for some immune responses among Eurygaster integriceps, Ephestia kuehniella and Zophobas morio against the entomopathogenic fungus Beuveria bassiana,.

Some defense reactions including cuticular lipids, phagocytic activity, nodulation and hemolymph phenoloxidasec activity were compared in Eurygaster integriceps, Ephestia kuehniella and Zophobas morio exposed to five different B. bassiana isolates. The cuticular lipids were stimulating on conidia germination possibly with no fungicidal or fungistatic ability in epicuticular fatty acids. There was correlation between all studied immune system reactions and the virulence of isolates to E. kuehniella and E. integriceps. DE as a less virulent fungal isolate stimulated immune reactions in high levels in most experiments, despite of TV as the most virulent isolate. E. integriceps was the most sensitive host with lowered immune reactions. Z. morio showed resistant with the highest nodulation. E. kuehniella had moderate sensitivity with maximal phagocytic and the phenoloxidase activity. The phagocytic activity was the highest at 30 min after fungus injection. The nodulation and the phenoloxidase activity were demonstrated at 6, 12 and 24 h after injection. The most nodulation rate was observed at 24 h. The phenoloxidase activity for the most isolates reached a maximum value for Z. morio and E. integriceps after 12 h and in E. kuehniella after 24 h. Our research provides an interesting perspective in host susceptibility to fungal infections.

Fungal infection dynamics in response to temperature in the lepidopteran insect Galleria mellonella.

This study examines how the dynamics of fungus-insect interactions can be modulated by temperature. The wax moth, Galleria mellonella, is a well-studied and important model insect whose larvae in the wild develop optimally at around 34 °C in beehives. However, surprisingly little research on wax moths has been conducted at relevant temperatures. In this study, the entomopathogenic fungus Metarhizium robertsii inflicted rapid and substantial mortality on wax moth larvae maintained at a constant temperature of 24 °C, but at 34 °C a 10 fold higher dose was required to achieve an equivalent mortality. The cooler temperature favored fungal pathogenicity, with condial adhesion to the cuticle, germination and hemocoel invasion all significantly enhanced at 24 °C, compared with 34 °C. The wax moth larvae immune responses altered with the temperature, and with the infective dose of the fungus. Enzyme-based immune defenses (lysozyme and phenoloxidase) exhibited enhanced activity at the warmer temperature. A dramatic upregulation in the basal expression of galiomicin and gallerimycin was triggered by cooling, and this was augmented in the presence of the fungus. Profiling of the predominant insect epicuticular fatty acids revealed a 4-7 fold increase in palmetic, oleic and linoleic acids in larvae maintained at 24 °C compared with those at 34 °C, but these failed to exert fungistatic effects on topically applied fungus. This study demonstrates the importance of choosing environmental conditions relevant to the habitat of the insect host when determining the dynamics and outcome of insect/fungus interactions, and has particular significance for the application of entomopathogens as biocontrol agents.

New insights into the infection of the American cockroach Periplaneta americana nymphs with Metarhizium anisopliae s.l. (Ascomycota: Hypocreales).

To study the marked resistance of Periplaneta americana to entomopathogenic Metarhizium anisopliae. The low susceptibility of 4th instar nymphs applied topically with conidia seemed to be related to an active removal of conidia by the cockroach and to a disabled or retarded germination and subsequent development of conidia on the cuticle (up to 80% germination in the next 7days after application). Inhibitions or delays of germination were related to the composition of the epicuticular fatty acids (30·1% w/w oleic, 28·3% w/w linoleic, 24·5% w/w palmitic and 11·7% w/w stearic acid) reported here. Propagules invading the nymphs through the cuticle took at least 3days to reach the haemocoel, and no propagules were found after day 8 post-treatment. Strain IP 46 infected >50% of nymphs treated with doses ≥2×104 hyphal bodies (HB)nymph-1 and reduced the survival of nymphs ≤50%. Most nymphs (>70%) survived after injection of 6×103 and 2×103 HBnymph-1 . Findings emphasize a distinct resistance of nymphs of the American cockroach to infections by M.anisopliae. Our findings provide support for the development of biological control of this synanthropic cockroach pest.

Allocation of freshly assimilated carbon into primary and secondary metabolites after in situ13C pulse labelling of Norway spruce (Picea abies)

Plants allocate carbon (C) to sink tissues depending on phenological, physiological or environmental factors. We still have little knowledge on C partitioning into various cellular compounds and metabolic pathways at various ecophysiological stages. We used compound-specific stable isotope analysis to investigate C partitioning of freshly assimilated C into tree compartments (needles, branches and stem) as well as into needle water-soluble organic C (WSOC), non-hydrolysable structural organic C (stOC) and individual chemical compound classes (amino acids, hemicellulose sugars, fatty acids and alkanes) of Norway spruce (Picea abies) following in situ (13)C pulse labelling 15 days after bud break. The (13)C allocation within the above-ground tree biomass demonstrated needles as a major C sink, accounting for 86% of the freshly assimilated C 6 h after labelling. In needles, the highest allocation occurred not only into the WSOC pool (44.1% of recovered needle (13)C) but also into stOC (33.9%). Needle growth, however, also caused high (13)C allocation into pathways not involved in the formation of structural compounds: (i) pathways in secondary metabolism, (ii) C-1 metabolism and (iii) amino acid synthesis from photorespiration. These pathways could be identified by a high (13)C enrichment of their key amino acids. In addition, (13)C was strongly allocated into the n-alkyl lipid fraction (0.3% of recovered (13)C), whereby (13)C allocation into cellular and cuticular exceeded that of epicuticular fatty acids. (13)C allocation decreased along the lipid transformation and translocation pathways: the allocation was highest for precursor fatty acids, lower for elongated fatty acids and lowest for the decarbonylated n-alkanes. The combination of (13)C pulse labelling with compound-specific (13)C analysis of key metabolites enabled tracing relevant C allocation pathways under field conditions. Besides the primary metabolism synthesizing structural cell compounds, a complex network of pathways consumed the assimilated (13)C and kept most of the assimilated C in the growing needles.

Environmental factors affecting the lipid metabolism in Rosmarinus officinalis L

The effect of some environmental factors on the lipid metabolism was studied in two chemotypes of Rosmarinus officinalis L. Epicuticular hydrocarbons (EH), epicuticular fatty acids (EFA), whole leaf fatty acids (WLFA) and essential oils (EO) were extracted and analysed by GC-MS during winter 1991–1992 and related to temperature and moisture variations. Leaf fresh and dry wts were determined along with some morphophysiological parameters such as specific leaf weight (SLW) and specific leaf area (SLA). Leaf areas were calculated by image analysis and statistically processed as for chemical data. The results indicated that in R. officinalis the response to some environmental factors, with particular reference to temperature and moisture, was an increase in epicuticular hydrocarbons and a decrease in epicuticular fatty acids, leaf fatty acids and essential oils. Qualitative changes in the chemical composition of the above lipid classes were found to be correlated with temperature changes. From a chemosystematic viewpoint, a clear separation between the two chemotypes was achieved only when epicuticular hydrocarbons and essential oils were considered as chemosystematic characters.

Epicuticular Fatty Acid, Fatty Alcohol, and Alkane Contents of Bloom and Bloomless Sorghum ‘Redbine 60’ Leaves1

Bloom and bloomless sorghum, Sorghum bicolor (L.) Moench, ‘Redbine 60’ are near isogenic lines differing in the presence or absence of a white, powdery‐appearing epicuticular leaf wax which influences plant water relations and animal utilization and whose genetic control and morphological characteristics have been published. Chemical evaluations of bloom and bloomless leaf epicuticular waxes are absent. Waxes were extracted with chloroform, esterified, separated into classes via thin‐layer chromatography, and quantitated via gas‐liquid chromatography utilizing polar and non‐polar columns and relative response curves from pure standard compounds. In leaves of equal density, leaves of the bloomless near‐isogenic line had epicuticular fatty acid, fatty alcohol, and alkane contents that were 73, 118, and 1%, respectively, of those constituents on bloom leaves. There was a 57% reduction on the bloomless leaf of total fatty acids + fatty alcohols + alkanes compared to the bloom leaf. Fatty alcohols longer than C20 were absent from the epicuticular wax of the bloom line. Alkane contents longer than C32 were essentially absent from the bloomless line while the most prevalent alkanes present on the bloom line were C35‐C37.

Effect of light and temperature on epicuticular fatty acid and fatty alcohol of tobacco

Abstract Genetically uniform burley tobacco ( Nicotiana tabacum ) was grown under field and various controlled-environment conditions to determine whether environment influenced epicuticular alkane, fatty acid, and fatty-alcohol composition of the leaves. Quantity and quality of alkanes, fatty acids, and fatty alcohols were greatly influenced by environmental conditions. Highest light intensity did not result in the largest total long aliphatic carbon-chain production. Generally, long photoperiod and cool temperature were associated with highest long aliphatic carbon-chain production on a leaf area basis. Quantity of the individual alkane, fatty acid, or fatty alcohol classes present under the different growth conditions varied in relation to the leaf metabolic status and not leaf size.

Effect of light and temperature on epicuticular fatty acid and fatty alcohol of tobacco

Effect of light and temperature on epicuticular fatty acid and fatty alcohol of tobacco

Sicklepod Surface Wax Response to Photoperiod and S-(2,3-Dichloroallyl)diisopropylthiocarbamate (Diallate)

Sicklepod (Cassia obtusifolia L.) leaflet epicuticular fatty acid, fatty alcohol, and hydrocarbon contents were measured by gas-liquid chromatography from plants grown under 10-, 12-, 14-, or 16-hour photoperiods and treated with S-(2,3-dichloroallyl)diisopropylthiocarbamate (diallate) (0, 0.14, 0.28, 0.56, 1.12 kilograms per hectare). As diallate concentration increased, epicuticular fatty acid content decreased. Fatty alcohol content was maximal in plants treated with 0.28 kilograms per hectare diallate and was reduced from that level at herbicide concentrations above or below this rate. Hydrocarbon content patterns were similar to those of the fatty alcohols except that the hydrocarbons at 0.28 kilograms per hectare were 61% of that present in the control, whereas the concentration of fatty alcohols increased to 200% of the control in treatments of 0.28 kilograms per hectare diallate.Photoperiodic influence on the various epicuticular lipid classes showed increased fatty acid and hydrocarbon contents as the photoperiod was lengthened. Fatty alcohols were maximal under 16-hour photoperiods and minimal under 12-hour photoperiods.Photoperiod-diallate concentration interactions were demonstrated in the epicuticular fatty acid, fatty alcohol, and hydrocarbon contents of sicklepod leaflets. The amount of each lipid class present per gram leaf fresh weight was influenced by the rate of diallate applied and the photoperiod under which the plants were grown. Each lipid class responded differently to the combination of treatments.