Influence of Some Fatty Acids on Oviposition by the Bruchid Beetle, Callosobruchus maculatus

The cowpea seed beetle, Callosobruchus maculatus, will lay its eggs on many potential hosts and inert surfaces. Oviposition on glass beads is stimulated by coating them with individual fatty acids. Nevertheless, female beetles reject mung seeds less frequently than beads treated with either an extract of mung seeds or, especially, an extract of mung seeds plus oleic acid. The addition of oleic acid to the extract resulted in a change in the sequence of oviposition behavior, notably an increase in a raised body position indicative of hosts of low acceptability. Fatty acids are present in the epicuticular waxes of legume seeds; wax extract of mung bean contains 32.4% fatty acid and 14 alkanes, whereas a wax extract of chickpea contains 5% fatty acid and 18 alkanes. Thus, chickpea may be a less acceptable host for oviposition than mung bean because of physical differences and/or because of chemical differences, including a reduced total level of fatty acid or the high proportion of oleic acid it is reported to contain. It is concluded that an appropriate mixture of fatty acids in the epicuticular waxes stimulates oviposition but that an elevated level of oleic acid in conjunction with others is deterrent.     

Identification of Unique Aldehyde Dimers in Sorghum Wax Recovered after Fermentation in a Commercial Fuel Ethanol Plant

Sorghum wax can be extracted from the surface of sorghum (Sorghum bicolor) kernels. It is composed mostly of a mixture of unsaturated C₂₈ and C₃₀ alkanes, fatty acids, fatty alcohols, and fatty aldehydes. Like carnauba wax, sorghum wax is a hard wax with a high melting point and it has potential edible and industrial applications. The yield of sorghum wax from the surface of sorghum kernels is 0.2–0.5 g of wax per 100 g of kernels. Sorghum wax can also be recovered from the “distillers oil” which is obtained after fermentation of sorghum (milo) or sorghum/corn blends in dry grind fuel ethanol plants. This distillers sorghum wax can potentially be obtained in yields of up to 10% by chilling the distillers oil to precipitate the wax and then recovering it via centrifugation or filtration. Like sorghum kernel wax, distillers sorghum wax is mainly composed of C₂₈ and C₃₀ alkanes, alcohols, and aldehydes in the molecular weight (MW) range of 350–450. However, we found that 7–49% w/w of distillers sorghum wax is composed of larger wax components with MW of 799–912. Analysis via high-resolution atmospheric pressure chemical ionization mass spectrometry (APCI) and gas chromatography with electron ionization mass spectrometry (GC/MS-EI) resulted in exact mass data and fragmentation patterns that suggested that these high MW compounds are monounsaturated fatty aldehyde dimers, likely formed by aldol condensation. Further confirmation supporting the GC/MS data for the aldol reaction was obtained by comparison with similar aldol products.     

Dissecting the Roles of Cuticular Wax in Plant Resistance to Shoot Dehydration and Low-Temperature Stress in Arabidopsis

Cuticular waxes are a mixture of hydrophobic very-long-chain fatty acids and their derivatives accumulated in the plant cuticle. Most studies define the role of cuticular wax largely based on reducing nonstomatal water loss. The present study investigated the role of cuticular wax in reducing both low-temperature and dehydration stress in plants using Arabidopsis thaliana mutants and transgenic genotypes altered in the formation of cuticular wax. cer3-6, a known Arabidopsis wax-deficient mutant (with distinct reduction in aldehydes, n-alkanes, secondary n-alcohols, and ketones compared to wild type (WT)), was most sensitive to water loss, while dewax, a known wax overproducer (greater alkanes and ketones compared to WT), was more resistant to dehydration compared to WT. Furthermore, cold-acclimated cer3-6 froze at warmer temperatures, while cold-acclimated dewax displayed freezing exotherms at colder temperatures compared to WT. Gas Chromatography-Mass Spectroscopy (GC-MS) analysis identified a characteristic decrease in the accumulation of certain waxes (e.g., alkanes, alcohols) in Arabidopsis cuticles under cold acclimation, which was additionally reduced in cer3-6. Conversely, the dewax mutant showed a greater ability to accumulate waxes under cold acclimation. Fourier Transform Infrared Spectroscopy (FTIR) also supported observations in cuticular wax deposition under cold acclimation. Our data indicate cuticular alkane waxes along with alcohols and fatty acids can facilitate avoidance of both ice formation and leaf water loss under dehydration stress and are promising genetic targets of interest.     

Leaf Epicuticular Wax Chemicals of the Japanese Knotweed Fallopia japonica as Oviposition Stimulants for Ostrinia latipennis

Extraction, fractionation, and gas chromatography−mass spectrometry analyses guided by bioassays have shown that n-alkanes and free fatty acids in leaf epicuticular wax of the Japanese knotweed Fallopia (Reynoutria) japonica stimulate oviposition in the Far-Eastern knotweed borer, Ostrinia latipennis (Lepidoptera: Crambidae). n-Alkanes made up 48.1% of the total amount of epicuticular wax, and their carbon chain length was in the C₁₆−C₃₃ range, with n-nonacosane (n-C₂₉) most abundant, followed by n-C₂₇, n-C₂₅, and n-C₃₁. Free fatty acids with C₉−C₂₂ accounted for 22.3%, and hexadecanoic acid was predominant. A mixture of authentic n-alkanes and fatty acids of the composition found in the epicuticular wax, a mixture of n-alkanes, and a mixture of fatty acids significantly enhanced oviposition. Thus, it was demonstrated that both n-alkanes and free fatty acids in leaf epicuticular wax of F. japonica are naturally occurring oviposition stimulants for O. latipennis.     

The Combination of Abscisic Acid (ABA) and Water Stress Regulates the Epicuticular Wax Metabolism and Cuticle Properties of Detached Citrus Fruit

The phytohormone abscisic acid (ABA) is a major regulator of fruit response to water stress, and may influence cuticle properties and wax layer composition during fruit ripening. This study investigates the effects of ABA on epicuticular wax metabolism regulation in a citrus fruit cultivar with low ABA levels, called Pinalate (Citrus sinensis L. Osbeck), and how this relationship is influenced by water stress after detachment. Harvested ABA-treated fruit were exposed to water stress by storing them at low (30–35%) relative humidity. The total epicuticular wax load rose after fruit detachment, which ABA application decreased earlier and more markedly during fruit-dehydrating storage. ABA treatment changed the abundance of the separated wax fractions and the contents of most individual components, which reveals dependence on the exposure to postharvest water stress and different trends depending on storage duration. A correlation analysis supported these responses, which mostly fitted the expression patterns of the key genes involved in wax biosynthesis and transport. A cluster analysis indicated that storage duration is an important factor for the exogenous ABA influence and the postharvest environment on epicuticular wax composition, cuticle properties and fruit physiology. Dynamic ABA-mediated reconfiguration of wax metabolism is influenced by fruit exposure to water stress conditions.     

Surface Composition of Myrmecophilic Plants: Cuticular Wax and Glandular Trichomes on Leaves of <Emphasis Type="Italic">Macaranga tanarius</Emphasis>

Primary plant surfaces, covered with cuticles consisting of cutin and waxes, are important substrates for interaction with insects. The composition of leaf surfaces of the myrmecophilic plant Macaranga tanarius was studied. The prenylated flavanone nymphaeol-C was identified in surface extracts and was localized exclusively in glandular trichomes on the abaxial leaf side. The epidermal pavement cells surrounding these trichomes were covered with a smooth film of epicuticular wax from which few small wax crystals protruded. The epicuticular wax amounted to approximately 8 μg cm⁻², corresponding to 85% of the wax load on the adaxial as well as the abaxial leaf sides. The epicuticular wax mixtures from both leaf surfaces contained more than 70% primary alcohols, 14% fatty acids, 2% aldehydes, and traces of alkyl acetates, with chain lengths ranging from C₂₀ to C₃₈. In contrast, the intracuticular wax layer was largely dominated by triterpenoid alcohols α-amyrin, β-amyrin, and lupeol. Consequently, these characteristic compounds are not available for direct contact with insects on the plant surface.     

Extraction and composition of volatiles from Zanthoxylum rhesta: Comparison of subcritical CO2 and traditional processes

The dried fruits of Zanthoxylum rhesta DC syn Z. budrungawall syn. Z. limonella (Dennst) are used as condiments and have spice value. While the essential oil is concentrated in the pericarp, the seeds have fatty oil. The extraction of fragrance/flavour components is carried out from the pericarp by subcritical CO₂, modified methanol–subcritical CO₂, hydrodistillation and traditional solvent extraction processes and the composition of these extracts are compared. The components are identified by GC–MS and the composition is determined by GC–FID. The principal components such as sabinene, terpinen-4-ol, α-terpineol are present in different amounts in the extracts. The traditional solvent extraction processes provide more amounts of waxy components along with the principal components. Though hydrodistillation process provides a wax free essential oil, the yield is low. The extract obtained by the subcritical CO₂ method is superior in comparison to traditional processes, but it contains higher percentage of monoterpenes in comparison to oxygenated monoterpenes. On the other hand, extraction of all the desired components is possible through pre-treatment of pericarp by small amounts of methanol. These details are described and discussed.     

Epicuticular waxes of maize as affected by the interaction of mutantgl8 withgl3, gl4 andgl15

Chemical composition of epicuticular waxes from double mutants of maizegl2gl8, gl3gl8, gl4gl8 andgl15gl8 is compared to that of the wild type and of the single mutants. The wax composition was moderately affected in the double mutants studied. Meanwhile, free fatty acids became a normal class constituent of the waxes. The sites of action of the single mutants as deduced from previous studies are confirmed. The influence ofgl2, gl3 andgl4 on the terminal steps of the chain elongation process ingl2gl8, gl3gl8 andgl4gl8 genotypes is presented and discussed. The study ofgl3gl8 waxes also confirms that the mutantgl3 induces a metabolic defect defiitely different from those ofgl2 andgl4. The pattern of alkanes fromgl15gl8 is unusual, supporting the thesis thatgl15 controls mainly alkane synthesis. However, based on variations induced on wax composition, its manner of action is difficult to account for. Taken together, the available data on single and double mutants affecting wax synthesis in maize suggest that elongases might be heteromeric enzymes.     

Host Sex Discrimination by an Egg Parasitoid on Brassica Leaves

Egg parasitoids are able to find their hosts by exploiting their chemical footprints as host location cues. In nature, the apolar epicuticular wax layer of plants that consists of several classes of hydrocarbons serves as the substrate that retains these contact kairomones. However, experiments on chemical footprints generally have used filter paper as substrate to study insect behavior. Here, we explored the ability of Trissolcus basalis (Scelionidae) females to discriminate between footprint cues left by male and female Nezara viridula (Pentatomidae) on leaves of their host plant Brassica oleracea (broccoli). Furthermore, we analyzed the chemical composition of the outermost wax layer of broccoli leaves to evaluate the degree of overlap in insect and plant cuticular hydrocarbons that could lead to masking effects in the detection of footprint cues. Our results showed that B. oleracea epicuticular wax retains the chemical footprints of adult bugs and allows T. basalis females to differentiate hosts of different sex. Traces of female bugs elicited more extensive searching behavior in egg parasitoids than traces of males. The application of n-nonadecane, a compound specific to male N. viridula, on the tarsi of female bugs prevented parasitoid females from distinguishing between host male and host female footprints. Analyses of B. oleracea leaves revealed that epicuticular waxes were mainly composed of linear alkanes, ketones, and secondary alcohols. Alkanes were dominated by n-nonacosane (nC29) and n-hentriacontane (nC31), while male-specific n-nonadecane (nC19) was absent. The ecological significance of these results for parasitoid host location behavior is discussed.     

Fatty acids,fatty alcohols,and wax esters fromLimnanthes douglassi (Meadowfoam) seed oil

Limanathes douglasii seed oil glycerides contain fatty acids which predominantly (97%) have 20 or more carbon atoms. Fatty acids were prepared by saponification; fatty alcohols, by sodium reduction of the glycerides; and liquid wax esters, byp-toluenesulfonic acid-catalyzed reaction of the fatty acids with the fatty alcohols. Solid waxes were prepared by hydrogenation of the glyceride oil and of the wax esters. Chemical and physical constants were determined forLimnanthes douglasii seed oil and its derivatives. The liquid wax esters had properties very similar to those of jojoba (Simmondsia chinensis) seed oil. The solid hydrogenated wax ester was identical in physical appearance and melting point to hydrogenated jojoba seed oil. A laboratory of the Northern Utilization Research and Development Division, Agricultural Research Service, USDA.     

Use of Essential Oils From Various Plants to Change the Fatty Acids Profiles of Lipids Obtained From Oleaginous Yeasts

We studied the ability of seven essential oils to alter the fatty acid composition of lipids produced by an oleaginous yeast Rhodosporidium toruloides. All of the essential oils, except thyme, significantly increased the stearic acid content of the lipids. The amount of essential oils in the media determined the fatty acid composition obtained. Subsequently, we studied the effect of the major monoterpenes present in these essential oils. When R. toruloides was grown on limonene, a major monoterpene in orange essential oil, the composition of lipid obtained was found to be quite similar to natural orange essential oil. This proved that limonene has a major role in the changes in fatty acid profiles of the lipids. The effect of orange essential oil on another oleaginous yeast, Cryptococcus curvatus, was also carried out. Although the effect of the essential oil on the fatty acid composition and biomass (cell mass) was similar for both these two yeasts, the reduction of the activity of some enzymes involved in the metabolic pathways was quite different. From these results, it can be concluded that the effect of essential oils differs with species and it is possible to produce lipids with alternate fatty acid profiles suitable for different applications and with good market value.     

Extraction,purification and characterization of wax from flax (Linum usitatissimum) straw

The chemical composition and selected physical parameters of wax extracted from flax straw with supercritical CO₂ (SC‐CO₂) and hexane have been determined. From the GC/MS results, clear variations in composition and component distributions were observed between SC‐CO₂‐ and hexane‐extracted samples. The major components of the SC‐CO₂ and hexane extracts from three flax cultivars were: fatty acids (36–49%), fatty alcohols (20–26%), aldehydes (10–14%), wax esters (5–12%), sterols (7–9%) and alkanes (4–5%). Purification of SC‐CO₂‐extracted wax with silica gel chromatography yielded 0.4–0.5% (dry matter) and was composed primarily of wax esters (C₄₄, C₄₆ and C₄₈) and alkanes (C₂₇, C₂₉ and C₃₁). UV‐Vis scans of the purified wax samples exhibited two main peaks indicating the presence of conjugated dienes and carotenoids or related compounds. Fourier transform infrared results showed prominent peaks at 2918 (‐C‐H), 2849 (‐C‐H), 1745 (‐C=O), 1462 (‐C‐H), 1169 (‐C‐O) and 719 cm^–1 (‐(CH₂)_n‐), with NorLin wax showing a slightly deviating pattern compared to the other samples. Thermal analysis by differential scanning calorimetry revealed a mean melting point of 55–56 °C and oxidation temperatures of 146–153 °C for purified wax from flax straw processed using different procedures.     

Analysis of paraffin precipitation from petroleum mixtures by means of DSC: Iterative procedure considering solid-liquid equilibrium equations

Wax deposition is a well known flow assurance risk in crude oil production due to temperature decrease which depends mainly on the crude oil nature and the type and content of paraffin. The prevention of this problem requires a detailed characterization of the crude oil and the availability of reliable predictive models.The experimental determination and quantification of the precipitation process is quite complex and time consuming and simpler techniques are of interest to carry out such study. Among them, differential scanning calorimetry (DSC) technique is appropriate to develop routine essays and has been extensively applied to determine wax appearance temperature in crude oil and fractions because the simplicity and fast response of the technique.However, the determination of wax precipitation curve from a quantitative DSC interpretation is usually based on pure n-alkane properties and involves some difficulties. In this work, a new procedure has been developed including the effect of the fluid composition on the precipitation temperature and the melting heat. Solid-liquid equilibrium equations were introduced through a simplified thermodynamic model in the integration procedure resulting in an iterative method combining experimental and calculated values. The final method yields the wax appearance temperature (WAT), the full wax precipitation curve and the estimated wax composition.In order to validate the procedure, several crude oil fractions were used as standards due to the advantage of a narrow n-alkane distribution. Experimental characterization for the cloud point temperature, the n-alkane distribution (determined by gas chromatography with mass detector, GCMS) and DSC was carried out. The agreement between experimental results and those obtained from the DSC interpretation is a good check for the proposed procedure.     

Fatty Acid Profile of Kenaf Seed Oil

The fatty acid profile of kenaf (Hibiscus cannabinus L.) seed oil has been the subject of several previous reports in the literature. These reports vary considerably regarding the presence and amounts of specific fatty acids, notably (12,13-epoxy-9(Z)-octadecenoic (epoxyoleic) acid, but also cyclic (cyclopropene and cyclopropane) fatty acids. To clarify this matter, two kenaf seed oils (from the Cubano and Dowling varieties of kenaf) were investigated regarding their fatty acid profiles. Both contain epoxyoleic acid, the Cubano sample around 2 % and the Dowling sample 5-6 % depending on processing. The cyclic fatty acids malvalic and dihydrosterculic were identified in amounts around 1 %. Trace amounts of sterculic acid were observed as were minor amounts of C17:1 fatty acids. The results are discussed in the context of the fatty acid profiles of other hibiscus seed oils.     

Identification and Functional Characterization of Acyl-ACP Thioesterases B (GhFatBs) Responsible for Palmitic Acid Accumulation in Cotton Seeds

In spite of increasing use in the food industry, high relative levels of palmitic acid (C16:0) in cottonseed oil imposes harmful effects on human health when overconsumed in the diet. The limited understanding of the mechanism in controlling fatty acid composition has become a significant obstacle for breeding novel cotton varieties with high-quality oil. Fatty acyl–acyl carrier protein (ACP) thioesterase B (FatBs) are a group of enzymes which prefer to hydrolyze the thioester bond from saturated acyl-ACPs, thus playing key roles in controlling the accumulation of saturated fatty acids. However, FatB members and their roles in cotton are largely unknown. In this study, a genome-wide characterization of FatB members was performed in allotetraploid upland cotton, aiming to explore the GhFatBs responsible for high accumulations of C16:0 in cotton seeds. A total of 14 GhFatB genes with uneven distribution on chromosomes were identified from an upland cotton genome and grouped into seven subfamilies through phylogenetic analysis. The six key amino acid residues (Ala, Trys, Ile, Met, Arg and Try) responsible for substrate preference were identified in the N-terminal acyl binding pocket of GhFatBs. RNA-seq and qRT-PCR analysis revealed that the expression profiles of GhFatB genes varied in multiple cotton tissues, with eight GhFatBs (GhA/D-FatB3, GhA/D-FatB4, GhA/D-FatB5, and GhA/D-FatB7) having high expression levels in developing seeds. In particular, expression patterns of GhA-FatB3 and GhD-FatB4 were positively correlated with the dynamic accumulation of C16:0 during cotton seed development. Furthermore, heterologous overexpression assay of either GhA-FatB3 or GhD-FatB4 demonstrated that these two GhFatBs had a high substrate preference to 16:0-ACP, thus contributing greatly to the enrichment of palmitic acid in the tested tissues. Taken together, these findings increase our understanding on fatty acid accumulation and regulation mechanisms in plant seeds. GhFatBs, especially GhA-FatB3 and GhD-FatB4, could be molecular targets for genetic modification to reduce palmitic acid content or to optimize fatty acid profiles in cotton and other oil crops required for the sustainable production of healthy edible oil.     

Diacylglycerol Acyltransferase 3(DGAT3) Is Responsible for the Biosynthesis of Unsaturated Fatty Acids in Vegetative Organs of Paeonia rockii

‘Diacylglycerol acyltransferase (DGAT)’ acts as a key rate-limiting enzyme that catalyzes the final step of the de novo biosynthesis of triacylglycerol (TAG). The study was to characterize the function of the DGAT3 gene in Paeonia rockii, which is known for its accumulation of high levels of unsaturated fatty acids (UFAs). We identified a DGAT3 gene which encodes a soluble protein that is located within the chloroplasts of P. rockii. Functional complementarity experiments in yeast demonstrated that PrDGAT3 restored TAG synthesis. Linoleic acid (LA, C18:2) and α-linolenic acid (ALA, C18:3) are essential unsaturated fatty acids that cannot be synthesized by the human body. Through the yeast lipotoxicity test, we found that the yeast cell density was largely increased by adding exogenous LA and, especially, ALA to the yeast medium. Further ectopic transient overexpression in Nicotiana benthamiana leaf tissue and stable overexpression in Arabidopsis thaliana indicated that PrDGAT3 significantly enhanced the accumulation of the TAG and UFAs. In contrast, we observed a significant decrease in the total fatty acid content and in several major fatty acids in PrDGAT3-silenced tree peony leaves. Overall, PrDGAT3 is important in catalyzing TAG synthesis, with a substrate preference for UFAs, especially LA and ALA. These results suggest that PrDGAT3 may have practical applications in improving plant lipid nutrition and increasing oil production in plants.     

Premating Isolation Is Determined by Larval Rearing Substrates in CactophilicDrosophila mojavensis. III. Epicuticular Hydrocarbon Variation Is Determined by Use of Different Host Plants inDrosophila mojavensis andDrosophila arizonae

Adult epicuticular hydrocarbon profiles of male and femaleDrosophila mojavensis have been implicated as determinants of mate choice leading to premating isolation between geographically isolated populations. Hydrocarbon profiles of a Baja California and a mainland Sonora population ofDrosophila mojavensis, ayellow body mutant strain ofD. mojavensis, and a population ofD. arizonae were compared among flies that had been reared on two cactus substrates and a synthetic laboratory growth medium in order to assess the degree to which natural rearing substrates influence adult hydrocarbon composition. Twenty epicuticular hydrocarbon components, ranging from C₂₉ to C₄₁, were recovered by gas chromatography that represented major classes of alkanes, alkenes, and alkadienes. We found differences in relative amounts of epicuticular hydrocarbons among Baja and mainlandD. mojavensis, and theyellow body mutants. There were few differences betweenD. mojavensis andD. arizonae. The effects of rearing substrates were remarkable: most of the differences were due to the effects of lab food vs. cactus, but there were significant rearing substrate effects due to differences in the two cacti used. Eleven hydrocarbon components differed in abundance between males and females or showed significant sex × rearing substrate interactions from ANOVA. The effects of rearing substrates on epicuticular hydrocarbon composition inD. mojavensis are concordant with changes in the intensity of premating isolation between populations, implicating host ecology as a major determinant in patterns of mate choice in this species.     

Wax esters and triglycerides as storage substances in seeds of Buxus sempervirens

The seeds of the evergreen Buxus‐tree, Buxus sempervirens, contain a yellowish oil which represents up to 42% of the dry weight. The oil consists, in comparison to the lipids of jojoba fruits (Simmondsia chinensis), of only 3.6% wax esters. 95% of the oil consist of triglycerides, the typical storage substances of oil fruits. Phospholipids occur with 0.4% and glycolipids with 0.13%. The fatty acid patterns of these lipids correspond to the typical fatty acid compositions of the respective lipid classes. In the wax esters monoenoic fatty acids and saturated fatty acids with 16 and 18 carbon atoms prevail. The glycolipid and phospholipid fractions are characterized by a high portion of dienoic and monoenoic as well as saturated fatty acids having 16 and 18 carbon acids.     

High molecular weight waxes from Short Path Distillates of vacuum residue

Short Path Distillates of vacuum residue (boiling above 545 °C) is taken as feedstock for this study. Wax from this fraction is separated by solvent extraction method using methyl iso-butyl ketone (MIBK) as solvent. Both wax and the feedstock are characterised with the help of ASTM and IP procedures. Separated wax is fractionated at different temperatures, say 0–30 °C using MIBK as solvent. High temperature gas chromatography (HTGC) technique is used to study the distribution of alkane carbon number in all the fractions. It is observed that the wax contains very high molecular weight hydrocarbons as high as C₆₇H₁₃₆. HTGC technique as well as the Differential Scanning Calorimetry (DSC) indicates that all the fractions of the wax contain two types of hydrocarbons, one having high molecular weight alkanes (> 600) and another having low mol. wt. alkanes (~ 400). Thermal analysis by DSC technique further indicates that the wax is microcrystalline in nature having a low degree of crystallinity, 17%, as evidenced by XRD studies. Both high and low molecular weight waxes can also be separated based on their solubility characteristics.