Wax Constituents Research Articles

Compositional analysis of tuberose floral cuticle sheds light on scent volatile emission and cuticle deposition

The plant cuticle acts as a vital shield, safeguarding against environmental and biological stresses. Tuberose flowers, specifically the ‘Calcutta Single’ and ‘Calcutta Double’ cultivars of Agave amica (syn. Polianthes tuberosa), are highly prized in India for their aromatic and aesthetic appeal. This research examines the tuberose floral cuticle using GC-MS to identify key chemical components and their characteristics. The analysis uncovered six major chemical classes viz. fatty acids, fatty alcohols, esters, alkanes, alkenes, and aldehydes as the primary constituents of the cuticular wax. Fatty acids and fatty alcohols are dominant in both cultivars, with ‘Calcutta Single’ displaying a higher ester content than ‘Calcutta Double’. This study represents the inaugural in-depth exploration of cuticular wax in tuberose flowers, presenting a comparative investigation into these prominent cultivars.

Cuticle deposition ceases during strawberry fruit development

BackgroundIdeally, the barrier properties of a fruit’s cuticle persist throughout its development. This presents a challenge for strawberry fruit, with their rapid development and thin cuticles. The objective was to establish the developmental time course of cuticle deposition in strawberry fruit.ResultsFruit mass and surface area increase rapidly, with peak growth rate coinciding with the onset of ripening. On a whole-fruit basis, the masses of cutin and wax increase but on a unit surface-area basis, they decrease. The decrease is associated with marked increases in elastic strain.The expressions of cuticle-associated genes involved in transcriptional regulation (FaSHN1, FaSHN2, FaSHN3), synthesis of cutin (FaLACS2, FaGPAT3) and wax (FaCER1, FaKCS10, FaKCR1), and those involved in transport of cutin monomers and wax constituents (FaABCG11, FaABCG32) decreased until maturity. The only exceptions were FaLACS6 and FaGPAT6 that are presumably involved in cutin synthesis, and FaCER1 involved in wax synthesis. This result was consistent across five strawberry cultivars.Strawberry cutin consists mainly of C16 and C18 monomers, plus minor amounts of C19, C20, C22 and C24 monomers, ω-hydroxy acids, dihydroxy acids, epoxy acids, primary alcohols, carboxylic acids and dicarboxylic acids. The most abundant monomer is 10,16-dihydroxyhexadecanoic acid. Waxes comprise mainly long-chain fatty acids C29 to C46, with smaller amounts of C16 to C28. Wax constituents are carboxylic acids, primary alcohols, alkanes, aldehydes, sterols and esters.ConclusionThe downregulation of cuticle deposition during development accounts for the marked cuticular strain, for the associated microcracking, and for their high susceptibility to the disorders of water soaking and cracking.

2-Methyloxolane as an effective bio-based solvent for the removal of βN-alkanoyl-5-hydroxytryptamines from Arabica green coffee beans

βN-alkanoyl-5-hydroxytryptamines (Cn-5HTs) are the main constituents of coffee wax and may be responsible for the increased severity of gastric disorders in sensitive consumers. Their removal from green coffee beans can result in a “stomach-friendly” brew. This work presents a green approach to Cn-5HTs extraction using the bio-based solvent 2-methyloxolane (2-MeOx). HPLC/DAD analyses on Arabica Brazil samples show that mild conditions (30 min at 50 °C) extract about 90% of the wax, without affecting the caffeine content of the beans, whereas almost complete removal is achieved in 60 min at reflux. 2-MeOx forms an azeotrope with water, its possible re-use has been demonstrated using aqueous 2-MeOx (95.5%) as the solvent. These preliminary results make 2-MeOx a possible candidate for the replacement of dichloromethane (DCM) in coffee dewaxing.The importance of fermentation in reducing Cn-5HTs by about 36% has been demonstrated in an analysis of green beans subjected to different post-harvest treatments.

Sustainable Composite Materials Based on Carnauba Wax and Montmorillonite Nanoclay for Energy Storage.

Sustainable composite materials, including carnauba wax, can store energy in the form of latent heat, and containing the wax may allow form-stable melting and crystallization cycles to be performed. Here, it is shown that carnauba wax in the molten state and the abundant nanoclay montmorillonite form stable composites with mass ratios of 50-70% (w/w). Transmission electron microscopy analysis reveals the inhomogeneous distribution of the nanoclay in the wax matrix. Analyses with infrared and multinuclear solid-state nuclear magnetic resonance (NMR) spectroscopy prove the chemical inertness of the composite materials during preparation. No new phases are formed according to studies with powder X-ray diffraction. The addition of the nanoclay increases the thermal conductivity and prevents the leakage of the phase change material, as well as reducing the time intervals of the cycle of accumulation and the return of heat. The latent heat increases in the row 69.5 ± 3.7 J/g, 95.0 ± 2.5 J/g, and 107.9 ± 1.7 J/g for the composite materials containing resp. 50%, 60% and 70% carnauba wax. Analysis of temperature-dependent 13C cross-polarization solid-state NMR spectra reveal the enhanced amorphization and altered molecular dynamics of the carnauba wax constituents in the composite materials. The amorphization also defines changes in the thermal transport mechanism in the composites compared to pure wax at elevated temperatures.

Study on the Effect of Nano Pour Point Depressant on Wax Oil Crystallization

The influence of nano pour point depressant (NPPD) on crude oil containing wax is primarily manifested through their interaction with the wax constituents. This study examines the depressant's effects using a polarizing microscope and an atomic force microscope (AFM) to assess morphological and structural changes in the wax crystals within the oil, both before and after the addtion of the NPPD. Additionally, a surface tensiometer measured surface tension, while a rheometer evaluated viscosity and modulus alterations. These methods facilitated insights into NPPD's mechanistic effects. The interaction process between crude oil wax crystal molecules and the main components of NPPD was simulated using JOCTA molecular dynamics simulation software, and the highest interaction strength between benzenesulfonic acid groups and crude oil wax crystal molecules was determined. The findings indicate that the addition of the NPPD alters the growth patterns and crystalline structure of the wax in the oil. Initially, the wax crystals present as flaky, predominantly single molecular layer lamellae with a thickness of approximately 100 nm. Post-treatment, the wax crystals adopt a flattened lamellar configuration, composed of multilayer lamellae, with a reduced thickness of within 10 nm and exhibiting short-range order. AFM height maps reveal an increase in the average roughness of the wax oil correlated with the addition of the NPPD across different sampling lengths. Surface tension measurements demonstrate that the wax oil doped with the NPPD exhibits lower surface tension than undoped oil, with the surface tension decreasing as the temperature increases.

Elevated nitrogen fertilization differentially affects jojoba wax phytochemicals, fatty acids and fatty alcohols.

Jojoba wax is gaining popularity among cosmetics consumers for its skin wound healing and rejuvenation bioactivities, attributed to collagen and hyaluronic acid synthesis. However, information regarding wax phytochemical composition and quality parameters, as well as effect of cultivation practices, and fertilization in particular, on wax quality is limited. The aim of the current work was to study the effect of nitrogen (N) availability to jojoba plants on wax phytochemical composition and beneficial skin-related contents. For this, wax quality from a six-year fertilization experiment with five N application levels was evaluated. The chemical parameters included antioxidant activity, free fatty acid, total tocopherol, total phytosterol and oxidative stability, as well as fatty acid and fatty alcohol profile. Our results reveal that the majority of wax quality traits were affected by N fertilization level, either positively or negatively. Interestingly, while fatty acids were unaffected, fatty alcohol composition was significantly altered by N level. Additionally, fruit load also largely affected wax quality, and, due to jojoba's biennial alternate bearing cycles, harvest year significantly affected all measured parameters. Results shed light on the effects of N application on various biochemical constituents of jojoba wax, and imply that N availability should be considered part of the entire agricultural management plan to enhance wax quality. Some traits are also suggested as possible chemical quality parameters for jojoba wax.

Multi-omics analysis of pigmentation related to proanthocyanidin biosynthesis in brown cotton (Gossypium hirsutum L.).

Naturally-colored brown cotton (NBC) fiber is an environmentally friendly raw source of fiber for textile applications. The fiber of some NBC cultivars exhibits flame-retardant properties, which can be used in textiles that require flame resistance. Proanthocyanidins or their derivatives are responsible for the brown pigment in NBC; however, how flame retardancy is related to pigmentation in NBC is poorly understood. To gain insight into brown pigment biosynthesis, we conducted comparative transcripts and metabolites profiling analysis of developing cotton fibers between the brown (MC-BL) and white (MC-WL) cotton near-isogenic lines (NILs), genetically different only in the Lc1 locus. In this study, mass spectrometry was used to detect metabolites in BL and WL developing fibers at 8, 12, 16, 20, 24, 36, and 40 days post anthesis (DPA) and mature fibers. Transcripts analysis was performed at two critical fiber developmental points, 8 DPA (fiber elongation) and 20 DPA (secondary cell wall deposition). We found 5836 (ESI MS positive mode) and 4541 (ESI MS negative mode) metabolites significantly different accumulated between BL and WL. Among them, 142 were known non-redundant metabolites, including organic acids, amino acids, and derivatives of the phenylpropanoid pathway. Transcript analysis determined 1691 (8 DPA) and 5073 (20 DPA) differentially expressed genes (DEGs) between BL and WL, with the majority of DEGs down-regulated at 20 DPA. Organic acids of the citric acid cycle were induced, while most of the detected amino acids were reduced in the MC-BL line. Both cis- and trans-stereoisomers of flavan-3-ols were detected in developing MC-WL and MC-BL fibers; however, the gallocatechin and catechin accumulated multiple times higher. Gas chromatography-mass spectrometry (GC-MS) analysis of fatty acids determined that palmitic acid long-chain alcohols were the main constituents of waxes of mature fibers. Energy-dispersive X-ray spectrometry (EDS) analysis of mature fibers revealed that potassium accumulated three times greater in MC-BL than in MC-WL mature fibers. This study provides novel insights into the biosynthesis of pigments and its association with flame retardancy in NBC fibers.

Niche-specific modulation of long-chain n-alkanes degrading bacterial community and their functionality in forest habitats across the leaf litter-soil compartments

Long-chain n-alkanes are vital constituents of plant-derived wax, however, their limited reactivity, life cycle in terms of biodegradation, and ecological impacts are not lucid in a niche-specific manner. Here, we provide an insight into the bacterial community and their functional variations associated with long-chain n-alkanes degradation across leaf litter-soil compartments in three rainforest habitats aiming to elucidate the microbial modulation linked to the long-chain n-alkanes concentration and composition. The ravine habitat showed significantly higher long-chain n-alkanes concentration, bacterial diversity and functional genes than the windward and leeward habitats. Among the statistically significant genera (p < 0.05) Intrasporangium, Virgisporangium, Micromonospora, and Planomicrobium were more abundant in the ravine habitat than in the other two habitats. Interestingly, three statistically significant genera including Sphingobium, Tepidisphaera, and Methylobacterium showed a decrease abundance with increasing soil depths compared to their abundance in leaf litter. The correlation analysis revealed that Rhizobium, Pseudorhodoferax, Micromonospora, Dongia, Actinoplanes, Bdellovibrio, Ohtaekwangia, Planctomicrobium, Opitutus, Actinokineospora, Novosphingobium, and Methylobacterium were significantly in a positive relationship with alkB gene and most of the long-chain n-alkanes (C27 to C34). The ordination analysis further unveiled a strong association among the long-chain n-alkanes concentration, potential degraders and alkB gene within the ravine habitat. Additionally, we observed a decreasing trend in the abundance of bacterial taxa and related functional genes with decreasing the long-chain n-alkane concentration, suggesting n-alkane specific taxa modulation. Fundamentally, this study provides niche-specific evidence that the concentration of long-chain n-alkanes could contribute to a shift in bacterial diversity, abundance and function in forest habitats.

Wax Composition of Serbian Dianthus spp. (Caryophyllaceae): Identification of New Metabolites and Chemotaxonomic Implications.

Although ethnopharmacologically renowned, wax constituents of Dianthus species were sporadically studied. A combination of GC-MS analysis, synthesis, and chemical transformations enabled the identification of 275 constituents of diethyl-ether washings of aerial parts and/or flowers of six Dianthus taxa (Dianthus carthusianorum, D. deltoides, D. giganteus subsp. banaticus, D. integer subsp. minutiflorus, D. petraeus, and D. superbus) and one Petrorhagia taxon (P. prolifera) from Serbia. Seventeen of these constituents (nonacosyl benzoate, additional 12 benzoates with anteiso-branched 1-alkanols, eicosyl tiglate, triacontane-14,16-dione, dotriacontane-14,16-dione, and tetratriacontane-16,18-dione) and two additional synthesized eicosyl esters (angelate and senecioate) represent completely new compounds. The structures of the tentatively identified β-ketones were confirmed by analysis of the mass fragmentation of the corresponding pyrazoles and silyl enol ethers obtained by transformations of crude extracts and extract fractions. Silylation allowed the identification of 114 additional constituents, including a completely new natural product (30-methylhentriacontan-1-ol). The results obtained by multivariate statistical analyses showed that the chemical profile of Dianthus taxa's surface waxes is subject to both genetic and ecological factors, whereas the latter seemingly takes a more important role for the studied Dianthus samples.

Rotator Phases of Aliphatic Aldehydes and Implications for Wax Crystal Growth in Plants

The even C22–32 aliphatic aldehydes were synthesized and analyzed by differential scanning calorimetry and high-temperature X-ray diffraction. Aldehydes were determined to crystallize into triclinic, monoclinic, and orthorhombic lattices and undergo solid–solid transitions into the rotator (R) phase. All of the known R phases for the even and odd n-alkanes were observed for the even aldehydes. Further, binary mixtures of triacontanal and n-nonacosane, two representative constituents of plant cuticular waxes, were determined to be partially miscible at three compositions (25:75, 50:50, 75:25) and likewise possess R-type phases. Many plants exhibit mutations wherein the expression of aldehydes in cuticular waxes is significantly decreased. Afflicted mutants are often glabrous, devoid of epicuticular wax crystals, and suffer from increased cuticular permeability as well as drought intolerance. We propose that aldehydes serve as miscibility intermediaries and their R phases may provide a mechanism for wax crystal growth in plants.

Late-season biosynthesis of leaf fatty acids and n-alkanes of a mature beech (Fagus sylvatica) tree traced via 13CO2 pulse-chase labelling and compound-specific isotope analysis.

Leaf cuticular waxes play an important role in reducing evapotranspiration via diffusion. However, the ability of mature trees to regulate the biosynthesis of waxes to changing conditions (e.g., drought, light exposition) remain an open question, especially during the late growing season. This holds also true for one of the most widely distributed trees in Central Europe, the European beech tree (Fagus sylvatica L.). In order to investigate the ongoing formation of wax constituents like alkanes and fatty acids, we conducted a 13CO2 pulse-chase labelling experiment on sun-exposed and shaded branches of a mature beech tree during the late summer 2018. The 13C-label was traced via compound-specific δ13C isotope analysis of n-alkanes and fatty acids to determine the de-novo biosynthesis within these compound classes. We did not observe a significant change in lipid concentrations during the late growing season, but we found higher n-alkane concentrations in sun-exposed compared to shaded leaves in August and September. The n-alkane and fatty acid composition showed ongoing modifications during the late growing season. Together with the uptake and following subsequent decrease of the 13C-label, this suggests ongoing de-novo biosynthesis, especially of fatty acids in European beech leaves. Moreover, there is a high variability in the 13C-label among individual branches and between sun-exposed and shaded leaves. At the same time, sun-exposed leaves invest more of the assimilated C into secondary metabolites such as lipids than shaded leaves. This indicates that the investigated mature beech tree could adjust its lipid production and composition in order to acclimate to changes in microclimates within the tree crown and during the investigated period.

Roles of the MYB94/FUSED LEAVES1 (ZmFDL1) and GLOSSY2 (ZmGL2) genes in cuticle biosynthesis and potential impacts on Fusarium verticillioides growth on maize silks.

Maize silks, the stigmatic portions of the female flowers, have an important role in reproductive development. Silks also provide entry points for pathogens into host tissues since fungal hyphae move along the surface of the silks to reach the site of infection, i.e., the developing kernel. The outer extracellular surface of the silk is covered by a protective hydrophobic cuticle, comprised of a complex array of long-chain hydrocarbons and small amounts of very long chain fatty acids and fatty alcohols. This work illustrates that two previously characterized cuticle-related genes separately exert roles on maize silk cuticle deposition and function. ZmMYB94/FUSED LEAVES 1 (ZmFDL1) MYB transcription factor is a key regulator of cuticle deposition in maize seedlings. The ZmGLOSSY2 (ZmGL2) gene, a putative member of the BAHD superfamily of acyltransferases with close sequence similarity to the Arabidopsis AtCER2 gene, is involved in the elongation of the fatty acid chains that serve as precursors of the waxes on young leaves. In silks, lack of ZmFDL1 action generates a decrease in the accumulation of a wide number of compounds, including alkanes and alkenes of 20 carbons or greater and affects the expression of cuticle-related genes. These results suggest that ZmFDL1 retains a regulatory role in silks, which might be exerted across the entire wax biosynthesis pathway. Separately, a comparison between gl2-ref and wild-type silks reveals differences in the abundance of specific cuticular wax constituents, particularly those of longer unsaturated carbon chain lengths. The inferred role of ZmGL2 is to control the chain lengths of unsaturated hydrocarbons. The treatment of maize silks with Fusarium verticillioides conidia suspension results in altered transcript levels of ZmFDL1 and ZmGL2 genes. In addition, an increase in fungal growth was observed on gl2-ref mutant silks 72 hours after Fusarium infection. These findings suggest that the silk cuticle plays an active role in the response to F. verticillioides infection.

Stimulation of Physiological Processes in St. John’s Wort (Hypericum perforatum L.) Seedlings by Treatments with Triacontanol and Benzyladenine

Abstract Treatment of St. John’s wort plantlets with 1 µM triacontanol and 2 µM benzyladenine stimulates growth and metabolic processes, being an environmental-friendly approach for optimizing the cultivation of these valuable medicinal plants under controlled conditions. When the two growth regulators (a bioactive cuticular wax constituent and a cytokinin) are applied simultaneously, they act synergistically, enhancing each other’s effect on the biomass accumulation and on certain parameters of the photosynthetic light use efficiency, such as the effective quantum yield of photosystem II and the overall vitality index of the photosynthetic apparatus which performs the conversion of light energy into usable forms for carbon dioxide assimilation. The results concerning the interactions between the two externally applied growth regulators during the early development of St. John’s wort plants may lead to a more efficient cultivation of this herbal medicinal product, including the possibility to modulate the production of pharmacologically active metabolites.

Lipidomic, Transcriptomic, and BSA-660K Single Nucleotide Polymorphisms Profiling Reveal Characteristics of the Cuticular Wax in Wheat.

Plant epidermal wax helps protect plants from adverse environmental conditions, maintains the function of tissues and organs, and ensures normal plant development. However, the constituents of epidermal wax and the regulatory mechanism of their biosynthesis in wheat have not been fully understood. Wheat varieties with different wax content, Jinmai47 and Jinmai84, were selected to comparatively analyze their waxy components and genetic characteristics, using a combination of lipidomic, transcriptomic, and BSA-Wheat 660K chip analysis. Through lipidomic analysis, 1287 lipid molecules were identified representing 31 lipid subclasses. Among these, Diacylglycerols (DG), (O-acyl)-ω-hydroxy fatty acids (OAHFA), wax ester (WE), Triacylglycerols (TG), and Monoradylglycerols (MG) accounted for 96.4% of the total lipids in Jinmai84 and 94.5% in Jinmai47. DG, OAHFA, and WE were higher in Jinmai84 than in Jinmai47 with the content of OAHFA 2.88-fold greater and DG 1.66-fold greater. Transcriptome sequence and bioinformatics analysis revealed 63 differentially expressed genes related to wax biosynthesis. Differentially expressed genes (DEGs) were found to be involved with the OAHFA, DG, and MG of synthesis pathways, which enriched the wax metabolism pathway. Non-glaucous and glaucous bulks from a mapping population were used to identify single nucleotide polymorphisms (SNP) via 660K chip analysis. Two loci centered on chromosomes 2D and 4B were detected and the locus on 4B is likely novel. These data improve understanding of complex lipid metabolism for cuticular wax biosynthesis in wheat and lay the foundation for future detailed investigation of mechanisms regulating wax metabolism.

Variation in Petal and Leaf Wax Deposition Affects Cuticular Transpiration in Cut Lily Flowers

The vase life of cut flowers is largely affected by post-harvest water loss. Cuticular wax is the primary barrier to uncontrolled water loss for aerial plant organs. Studies on leaf cuticular transpiration have been widely conducted; however, little is known about cuticular transpiration in flowers. Here, the cuticular transpiration rate and wax composition of three lily cultivars were determined. The minimum water conductance of tepal cuticles was higher at the green bud than open flower stage. Lily cuticular transpiration exhibited cultivar- and organ-specific differences, where transpiration from the tepals was higher than leaves and was higher in the ‘Huang Tianba’ than ‘Tiber’ cultivar. The overall wax coverage of the tepals was higher compared to that of the leaves. Very-long-chain aliphatics were the main wax constituents and were dominated by n-alkanes with carbon (C) chain lengths of C27 and C29, and C29 and C31 in the tepal and leaf waxes, respectively. Primary alcohols and fatty acids as well as small amounts of alkyl esters, ketones, and branched or unsaturated n-alkanes were also detected in both tepal and leaf waxes, depending on the cultivar and organ. In addition, the chain-length distributions were similar between compound classes within cultivars, whereas the predominant C-chain lengths were substantially different between organs. This suggests that the less effective transpiration barrier provided by the tepal waxes may result from the shorter C-chain aliphatics in the tepal cuticle, compared to those in the leaf cuticle. These findings provide further insights to support the exploration of potential techniques for extending the shelf life of cut flowers based on cuticular transpiration barrier properties.

Preharvest application of 1-methylcyclopropene and Ethephon altered cuticular wax biosynthesis and fruit quality of apples at harvest and during cold storage

To investigate the roles of Harvista (a sprayable 1-methylcyclopropene, 1-MCP, available component is 150 g · hm-2) and Ethephon (1 mL · L-1) applied at preharvest in apple (Malus domestica Borkh. 'Golden Delicious') fruit cuticular wax biosynthesis, the expression of genes related to fruit cuticular wax biosynthesis and ethylene biosynthesis and signaling, ethylene production rate, respiration rate, wax constituents and structure, and fruit quality were determined at harvest and during cold storage. The results showed that 1-MCP inhibited the expression levels of ethylene biosynthesis and signaling-related genes, decreased fruit ethylene production, and inhibited the expression of MdLACS1, MdCER6, MdCER4 and MdWSD1, which resulted in decreases in alcohols, acids, and esters content in fruit cuticular wax. 1-MCP also reduced fruit dropping rate from 17.17% to 12%; maintained fruit firmness, soluble solids, titratable acidity during cold storage; showed about as one fifth in the total length and one third in the widest width of wax crack as that in control at harvest. In contrast, Ethephon produced the opposite effects. In conclusion, 1-MCP inhibited fruit ethylene biosynthesis and signaling, and influenced fruit cuticular wax biosynthesis. Thus, the fruit cuticular wax constituents and structure was altered, and the fruit quality were maintained at harvest and during cold storage. The results provide a new technology for improving apple fruit harvest and postharvest quality by preharvest application of sprayable 1-MCP.

Crystallinity and Water Vapor Permeability of n-Alkane, Alcohol, Aldehyde, and Fatty Acid Constituents of Natural Waxes

Crystallinity and Water Vapor Permeability of <i>n-</i>Alkane, Alcohol, Aldehyde, and Fatty Acid Constituents of Natural Waxes

R2R3-MYB genes coordinate conical cell development and cuticular wax biosynthesis in Phalaenopsis aphrodite.

Petals of the monocot Phalaenopsis aphrodite (Orchidaceae) possess conical epidermal cells on their adaxial surfaces, and a large amount of cuticular wax is deposited on them to serve as a primary barrier against biotic and abiotic stresses. It has been widely reported that subgroup 9A members of the R2R3-MYB gene family, MIXTA and MIXTA-like in eudicots, act to regulate the differentiation of conical epidermal cells. However, the molecular pathways underlying conical epidermal cell development and cuticular wax biosynthesis in monocot petals remain unclear. Here, we characterized two subgroup 9A R2R3-MYB genes, PaMYB9A1 and PaMYB9A2 (PaMYB9A1/2), from P. aphrodite through the transient overexpression of their coding sequences and corresponding chimeric repressors in developing petals. We showed that PaMYB9A1/2 function to coordinate conical epidermal cell development and cuticular wax biosynthesis. In addition, we identified putative targets of PaMYB9A1/2 through comparative transcriptome analyses, revealing that PaMYB9A1/2 acts to regulate the expression of cell wall-associated and wax biosynthetic genes. Furthermore, a chemical composition analysis of cuticular wax showed that even-chain n-alkanes and odd-chain primary alcohols are the main chemical constituents of cuticular wax deposited on petals, which is inconsistent with the well-known biosynthetic pathways of cuticular wax, implying a distinct biosynthetic pathway occurring in P. aphrodite flowers. These results reveal that the function of subgroup 9A R2R3-MYB family genes in regulating the differentiation of epidermal cells is largely conserved in monocots and dicots. Furthermore, both PaMYB9A1/2 have evolved additional functions controlling the biosynthesis of cuticular wax.

Leaf Surface Wax Chemicals in Trichosanthes anguina (Cucurbitaceae) Cultivars Mediating Short-Range Attraction and Oviposition in Diaphania indica.

Larval Diaphania indica (Saunders) (Lepidoptera: Crambidae) cause complete defoliation of Trichosanthes anguina L. and reduce crop yield in India. Females lay eggs on the leaf surface, and therefore leaf surface waxes are potentially involved in host selection. Alkanes and free fatty acids are the major constituents of leaf surface waxes, so a study was conducted to determine whether these wax constituents from three T. anguina cultivars (MNSR-1, Baruipur Long, and Polo No.1) could act as short-range attractants and oviposition stimulants in D. indica females. Twenty n-alkanes from n-C14 to n-C36 and 13 free fatty acids from C12:0 to C21:0 were detected in the leaf surface waxes of these cultivars. Heptadecane and stearic acid were predominant among n-alkanes and free fatty acids, respectively, in these cultivars. Females showed attraction towards one leaf equivalent surface wax of each of these cultivars against solvent controls (petroleum ether) in Y-tube olfactometer bioassays. A synthetic blend of heptadecane, eicosane, hexacosane, and stearic acid, a synthetic blend of hexacosane and stearic acid, and a synthetic blend of pentadecane and stearic acid comparable to amounts present in one leaf equivalent surface wax of MNSR-1, Baruipur Long, and Polo No.1, respectively, were short-range attractants and oviposition stimulants in D. indica. Female egg laying responses were similar to each of these blends, providing information that could be used to developing baited traps in integrated pest management (IPM) programs.

Very-Long-Chain Wax Constituents from Primula veris and P. acaulis: Does the Paradigm of Non-Branched vs. Branched Chain Dominance Universally Hold in all Plant Taxa?

Herein n-, iso- and anteiso-series of very-long-chained (VLC) alkanes (C21 -C35 ), fatty acid benzyl esters (FABEs; C20 -C32 ), and 2-alkanones (C23 -C35 ) were identified in the wax of Primula veris L. and P. acaulis (L.) L. (Primulaceae). For the very first time in a sample of natural origin, the presence of iso- and anteiso-VLC FABEs and 2-alkanones was unequivocally confirmed by synthetic work, derivatization, and NMR. It should be noted that the studied species produced unusually high amounts of branched wax constituents (e. g., >50 % of 2-alkanones were branched isomers). The domination of iso-isomers, probably biosynthesized from leucine-derived starters, is a unique feature in the Plant Kingdom. The plant organ distribution of these VLC compounds in P. acaulis samples (different habitats and phenological phases) pointed to their possible ecological value. This was supported by a eutectic behavior of binary blends of FABEs and alkanes, as well as by high UV-C absorption by FABEs.