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At least 127 records · Page 7Linked to original sources
PubMed2004

WIN1, a transcriptional activator of epidermal wax accumulation in Arabidopsis.

Epicuticular wax forms a layer of hydrophobic material on plant aerial organs, which constitutes a protective barrier between the plant and its environment. We report here the identification of WIN1, an Arabidopsis thaliana ethylene response factor-type transcription factor, which can activate wax deposition in overexpressing plants. We constitutively expressed WIN1 in transgenic Arabidopsis plants, and found that leaf epidermal wax accumulation was up to 4.5-fold higher in these plants than in control plants. A significant increase was also found in stems. Interestingly, approximately 50% of the additional wax could only be released by complete lipid extractions, suggesting that not all of the wax is superficial. Gene expression analysis indicated that a number of genes, such as CER1, KCS1, and CER2, which are known to be involved in wax biosynthesis, were induced in WIN1 overexpressors. This observation indicates that induction of wax accumulation in transgenic plants is probably mediated through an increase in the expression of genes encoding enzymes of the wax biosynthesis pathway.

Arabidopsis↗
PubMed1995

Do minke whales (Balaenoptera acutorostrata) digest wax esters?

Mammals are known to utilize wax esters with an efficiency of less than 50%. The purpose of the present study was to examine whether or not minke whales (Balaenoptera acutorostrata), which at times may eat considerable amounts of wax-ester-rich krill, represent an exception to this general pattern. Samples of fresh undigested forestomach, as well as colon, contents were obtained from minke whales (n 5) that had been feeding on krill (Thysanoessa inermis) for some time. The samples were analysed for dry mass, energy density, lipid content and the major lipid classes, including wax esters. The concentrations of wax esters were compared with previous estimates of dry-matter disappearance of the same type of prey using an in vitro technique, to calculate the dry-matter digestibility of wax esters (DMDwax). Wax esters contributed 21% of the energy and 47% of total lipids in the krill diet. The energy density of gut contents decreased by 50% after their passage from forestomach to the end of the colon. The DMDwax was 94.1 (SD 2.8)% (n 5). This high DMDwax and the occurrence of fatty alcohols, one of the products of wax-ester hydrolysis, in faeces show that minke whales are very efficient digesters of wax esters and absorb most of the energy-rich products of this process.

Animals↗
PubMed2006

Effect of surface waxes on the persistence of chlorpyrifos-methyl in apples, strawberries and grapefruits.

The effects of the cuticle and epicuticular waxes of grapefruit, strawberry and apple on the photodegradation and penetration of chlorpyrifos-methyl were studied. Photodegradation experiments were conducted by exposing the insecticide to the light of a xenon lamp in the presence of a film of wax extracted from the fruit surface. The half-life of chlorpyrifos-methyl irradiated in absence of waxes was 9.6 min. The half-lives of pesticide irradiated in the presence of wax extracts of apple, grapefruit and strawberry were 83, 34 and 26 min, respectively. In penetration studies, fruit with and without wax layers were treated with an aqueous suspension of pesticide. The penetration of the pesticide from the cuticle to the pulp was measured after 24 h. Samples without wax contained a higher total amount of insecticide than those with wax. No pesticide was detected in samples of apple and grapefruit pulp. Residues were detected in all fractions of strawberry. The waxes and cuticle appear to have some effect on the photodegradation and penetration of chlorpyrifos-methyl in fruit samples.

Chlorpyrifos↗
PubMed2005

What do microbes encounter at the plant surface? Chemical composition of pea leaf cuticular waxes.

In the cuticular wax mixtures from leaves of pea (Pisum sativum) cv Avanta, cv Lincoln, and cv Maiperle, more than 70 individual compounds were identified. The adaxial wax was characterized by very high amounts of primary alcohols (71%), while the abaxial wax consisted mainly of alkanes (73%). An aqueous adhesive of gum arabic was employed to selectively sample the epicuticular wax layer on pea leaves and hence to analyze the composition of epicuticular crystals exposed at the outermost surface of leaves. The epicuticular layer was found to contain 74% and 83% of the total wax on adaxial and abaxial surfaces, respectively. The platelet-shaped crystals on the adaxial leaf surface consisted of a mixture dominated by hexacosanol, accompanied by substantial amounts of octacosanol and hentriacontane. In contrast, the ribbon-shaped wax crystals on the abaxial surface consisted mainly of hentriacontane (63%), with approximately 5% each of hexacosanol and octacosanol being present. Based on this detailed chemical analysis of the wax exposed at the leaf surface, their importance for early events in the interaction with host-specific pathogenic fungi can now be evaluated. On adaxial surfaces, approximately 80% of Erysiphe pisi spores germinated and 70% differentiated appressoria. In contrast, significantly lower germination efficiencies (57%) and appressoria formation rates (49%) were found for abaxial surfaces. In conclusion, the influence of the physical structure and the chemical composition of the host surface, and especially of epicuticular leaf waxes, on the prepenetration processes of biotrophic fungi is discussed.

Fungi↗
PubMed2005

Overexpression of WXP1, a putative Medicago truncatula AP2 domain-containing transcription factor gene, increases cuticular wax accumulation and enhances drought tolerance in transgenic alfalfa (Medicago sativa).

The identification of leaf wax genes involved in stress tolerance is expected to have great potential for crop improvement. Here we report the characterization of a novel AP2 domain-containing putative transcription factor gene from the model legume Medicago truncatula. The gene, designated WXP1, is able to activate wax production and confer drought tolerance in alfalfa (Medicago sativa), the most important forage legume species in the world and a close relative of M. truncatula. The predicted protein of WXP1 has 371 aa; it is one of the longest peptides of all the single AP2 domain proteins in M. truncatula. WXP1 is distinctly different from the most studied genes in the AP2/ERF transcription factor family such as AP2s, CBF/DREB1s, DREB2s, WIN1/SHN1 and GL15. Transcript level of WXP1 is inducible by cold, abscisic acid and drought treatment mainly in shoot tissues in M. truncatula. Overexpression of WXP1 under the control of the CaMV35S promoter led to a significant increase in cuticular wax loading on leaves of transgenic alfalfa. Scanning electron microscopy revealed earlier accumulation of wax crystals on the adaxial surface of newly expanded leaves and higher densities of wax crystalline structures on both adaxial and abaxial surfaces of mature leaves. Gas chromatography-mass spectrometry analysis revealed that total leaf wax accumulation per surface area increased 29.6-37.7% in the transgenic lines, and the increase was mainly contributed by C30 primary alcohol. WXP1 overexpression induced a number of wax-related genes. Transgenic leaves showed reduced water loss and chlorophyll leaching. Transgenic alfalfa plants with increased cuticular waxes showed enhanced drought tolerance demonstrated by delayed wilting after watering was ceased and quicker and better recovery when the dehydrated plants were re-watered.

Amino Acid Sequence↗
PubMed1998

Comb wax effects on the ontogeny of honey bee nestmate recognition

We addressed the general question of how kin recognition cues develop by investigating cue differentiation between colonies of the honey bee, Apis mellifera. In honey bee colonies, exposure to the wax comb is a critical component of the development of kin recognition cues. In this study, we determined how the cues develop under natural conditions (in swarms), whether the genetic source and age of the wax affect cue ontogeny, and whether exposure to wax, as in normal development, affects preferential feeding among bees within social groups. Cue development in swarms coincided with wax production, rather than with the presence of brood or the emergence of new workers; this finding supported previous observations concerning the importance of wax in cue ontogeny. Effective cue development required a match between the genetic source of the workers attempting to enter the hive, the wax to which they were exposed, and the guards at the hive entrance. The wax must also have been exposed to the hive environment for some time. Cues gained from wax did not mask or override cues used in preferential feeding interactions; this finding supports the contention that two recognition systems, one for nestmate recognition and the other for intra-colonial recognition, are present. The results fit a general model for cue development in nestmate recognition that relies on the use of nesting materials as an intermediary; the evolutionary significance of this model is discussed. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed2000

A comparison of the composition of epicuticular wax from red raspberry (Rubus idaeus L.) and hawthorn (Crataegus monogyna Jacq.) flowers.

Epicuticular waxes have been characterised from the flowers of raspberry and hawthorn, on both of which adult raspberry beetles (Byturus tomentosus) can feed. The flower wax from both species had similar alkane profiles and also contained long-chain alcohols, aldehydes and fatty acids. The range of the carbon numbers detected for these classes of compounds was broadly similar in both but the relative amounts of each differed between species. Raspberry flower wax also contained fatty acid methyl esters, a group of compounds that has rarely been detected in plant epicuticular waxes, however, these were not observed in hawthorn flower wax. Long-chain alcohol-fatty acid esters with carbon numbers ranging from C36 to C48 were also detected in both plant species. However, an examination of their constituent acids indicated that in hawthorn the esters based on the C16 fatty acid predominated, whilst in raspberry flower wax, esters based on the C20 fatty acid were most abundant. Both species also contained pentacyclic triterpenoids, which accounted for, on average, over 16 and 48% of the total wax extracted from raspberry and hawthorn flowers respectively. In the former, ursolic and oleanolic acids accounted for over 90% of the pentacyclic triterpenes, whilst hawthorn flower wax, in addition to containing these acids, also contained high relative concentrations of both free and esterified alpha- and beta-amyrins.

Alcohols↗
PubMed1998

Influence of Epicuticular Waxes on the Photolysis of Pirimicarb in the Solid Phase.

The influence of epicuticular waxes extracted from different fruits on the photodegradation of pirimicarb (I) in the solid phase was studied. Waxes were extracted with CHCl(3) and CHCl(3)/CH(3)OH from nectarines (N), oranges (O(R)), and mandarin oranges (M). All of the waxes affect the qualitative behavior of the photodegradation of I: the formation of photoproducts N-formylpirimicarb (II) and demethylpirimicarb (III) was hindered. This influence was found to be independent of the light sources (sunlight or lamp > 290 nm) and of the solvents employed in the extraction of the waxes. The photodegradation rate (K(obs)) of I was reduced to a different extent by the presence of waxes, from N and O, and was increased from M (irrespective of the extraction solvent). The photodegradation rates of II and III were both reduced by all waxes, M included. The waxes extracted with CHCl(3)/CH(3)OH show a higher inhibition effect on K(obs) than those with CHCl(3). The scales of rate reduction were similar under sunlight and artificial light. Inhibition of the photodegradation rate does not correlate with UV absorbance of waxes or with their content on the surface of the fruits.

Journal Article↗
PubMed2001

Leaf cuticular waxes of potted rose cultivars as affected by plant development, drought and paclobutrazol treatments.

The present work was carried out to evaluate how plant growth and cultural practices influence the amount and composition of cuticular waxes on leaves of rose cultivars. The total amount of cuticular wax per leaf area was higher for rose cultivar Apollo Parade than for Charming Parade. Both cultivars had waxes dominated by alkanes, with the major alkanes being the C31 and C33 homologues. Primary alcohols were the next most abundant constituent class, with C26 as the dominant homologue. Compared with Charming Parade, Apollo Parade had higher proportions of its total wax load as primary alcohols but lower acids and aldehydes. The proportion of alkanes in the total load on these cultivars was similar. Commercially produced roses are routinely treated with paclobutrazol (PBZ) to retard growth. PBZ treatments caused a 10% increase in total wax load and changes in the proportions of certain wax constituents within 11 days of application. Notable was an increase in the total proportion of acids in the total load 25 days after PBZ application, primarily because of increased C28 acids. An alternative method of retarding plant growth is production of roses under limited water availability. When Apollo Parade roses experienced periods of moderate drought stress during production, the wax load per leaf area increased 14 and 8% above control levels at 24 and 38 days after imposition of drought, respectively. Drought caused similar changes in the proportions of individual wax constituents as did PBZ application.

Journal Article↗
PubMed1996

Mutants in Arabidopsis thaliana Altered in Epicuticular Wax and Leaf Morphology.

We report eight new mutants in Arabidopsis thaliana possessing altered leaf morphology and epicuticular wax. These were isolated from a T-DNA-mutagenized population using a visual screen for altered leaf reflectance, i.e. increased glaucousness or glossiness. The mutants were placed into three distinct classes based on alterations in overall plant morphology: knobhead (knb), bicentifolia (bcf), and wax. The four knb mutants formed callus-like growths in the axillary region of the rosette leaves and apical meristem, the two bcf mutants produced hundreds of narrow leaves, and the two wax mutants had leaves and stems that were more glossy than wild type and organs that fused during early development. Leaves of knb and bcf were more glaucous and abnormally shaped than wild type. Epicuticular wax crystals over knb and bcf leaf surfaces (where none were present on wild type) likely contributed to their more glaucous appearance. In contrast, the glossy appearance of the wax mutants was associated with a reduced epicuticular wax load on both leaves and stems. One representative from each phenotypic class was selected for detailed analyses of epicuticular wax chemistry. All three lines, knb1, bcf1, and wax1, had dramatic alterations in the total amounts and relative proportions of their leaf epicuticular wax constituents.

Journal Article↗
PubMed1977

Gluconeogenesis from storage wax in the cotyledons of jojoba seedlings.

The cotyledons of jojoba (Simmondsia chinensis) seeds contained 50 to 60% of their weight as intracellular wax esters. During germination there was a gradual decrease in the wax content with a concomitant rise in soluble carbohydrates, suggesting that the wax played the role of a food reserve. Thin layer chromatography revealed that both the fatty alcohol and fatty acid were metabolized. The disappearance of wax was matched with an increase of catalase, a marker enzyme of the gluconeogenic process in other fatty seedlings. Subcellular organelles were isolated by sucrose gradient centrifugation from the cotyledons at the peak stage of germination. The enzymes of the beta oxidation of fatty acid and of the glyoxylate cycle were localized in the glyoxysomes but not in the mitochondria. The glyoxysomes had specific activities of individual enzymes similar to those of the castor bean glyoxysomes. An active alkaline lipase was detected in the wax bodies at the peak stage of germination but not in the ungerminated seeds. No lipase was detected in glyoxysomes or mitochondria. After the wax in the wax bodies had been extracted with diethyl ether, the organelle membrane was isolated and it still retained the alkaline lipase. The gluconeogenesis from wax in the jojoba seedling appears to be similar, but with modification, to that from triglyceride in other fatty seedlings.

Journal Article↗
PubMed1996

BIOCHEMISTRY AND MOLECULAR BIOLOGY OF WAX PRODUCTION IN PLANTS.

The aerial surfaces of plants are covered with a wax layer that is primarily a waterproof barrier but that also provides protection against environmental stresses. The ubiquitous presence of cuticular wax is testimony to its essential function. Genetic and environmental factors influence wax quantity and composition, which suggests that it is an actively regulated process. The basic biochemistry of wax production has been elucidated over the past three decades; however, we still know very little about its regulation. This review presents a discussion along with new perspectives on the regulatory aspects of wax biosynthesis. Among the topics discussed are the partitioning of fatty acid precursors into wax biosynthesis and the elongation of fatty acids with particular emphasis on the nature of the acyl primer, and the role of ATP in fatty acid elongation. The recent cloning of wax biosynthetic genes and the transport of wax to plant surfaces are also discussed.

Journal Article↗
PubMed2004

[An evaluation of virtual waxing up system with haptic interface].

PURPOSE: The purpose of this experiment was to construct a system of waxing pattern using virtual reality in the odontological field. The success of operation with feedback on the maniphalanx sense of waxing is reported. METHODS: The constructed device was a system based on PHANToM DESKTOP (SensAble Technologies Inc.). This device includes six-degrees-of-freedom input and reproduction of the sense of touch by anti-power feedback. The software which controls this device enables four operations such as "Cutting down", "Piling up", "Melting", and "Finishing" to be applied to the virtual waxing pattern by virtual reality. Finally, the virtual waxing was examined by applying this system to a virtual abutment tooth. RESULTS: With six-degrees-of-freedom input and anti-power feedback, a virtual waxing and the designer's highly developed designs were successfully expressed regardless of the virtual space. CONCLUSIONS: 1. The virtual waxing up could be done by six-degrees-of-freedom input with the stylus in a virtual space. 2. The time taken for all these numerical values of corresponding rate of volume, occlusal, mesio-distal and bucco-lingual views to reach 100+/-5%ranged from 50 to 75 minutes, with an average of 63 minutes. 3. The virtual wax improvement showed the tendency to trace the passage of first arranging the volume, and straightening the outlook on the occlusal view at the end. 4. This system, which provides an interface between man machines, six-degrees-of-freedom input and anti-power feedback, has much in common with the existing waxing up and crafting. The demand for special technologies by technical persons and engineers can be kept to a minimum and application of the method can be expanded into education and to objective evaluations.

English Abstract↗
PubMed2000

Rheology of dental waxes.

OBJECTIVES: The rheological properties of waxes are of considerable interest in dentistry, yet the only adopted method of characterizing them in this respect is arbitrary and uninterpretable. The intention was to identify a means of doing so in an objective fashion and to apply it to a variety of products to establish the scope of behavior. METHOD: The modified Stokes' falling ball method was used to determine the apparent viscosity of 11 waxes over 25-45 degrees C under a wide range of loads and, therefore, strain rates. RESULTS: The falling ball method was demonstrated to be applicable over at least 7 orders of magnitude in viscosity, 7 in terminal velocity, and 3 in load. Waxes were shown to be pseudoplastic, lacking any identifiable yield point and having marked departures from Newtonian behavior. The pseudoplasticity followed a power law, the exponent of which (the pseudoplasticity parameter) was temperature dependent in a complex manner, but which showed a definite relationship to the reduced temperature, referred to the liquidus temperature. A master curve could not be constructed because of this variation, but also because of discontinuities in the isothermal contours attributed to stress-melting of components of the wax mixture. Stress-melting may in part account for the pseudoplasticity. SIGNIFICANCE: A standardized viscosity number has been defined at 30 degrees C and under 10 N load as the common logarithm of the falling ball apparent viscosity in order to characterize the flow behavior of dental waxes with a single convenient number. The shear thinning exponent, the reciprocal of the pseudoplasticity parameter, provides a similarly convenient measure of the stress-sensitivity of the wax. Direct objective comparison of the rheology of dental waxes may now be made, facilitating selection by the user through appropriate labeling.

Dental Materials↗
PubMed2003

Cuticular hydrocarbons and wax esters of the ectoparasitoid Habrobracon hebetor: Ontogenetic, reproductive, and nutritional effects.

Hydrocarbon and wax ester components of cuticular lipids of the braconid parasitoid Habrobracon hebetor Say reared at 25 degrees C on larvae of a pyralid moth have been identified by GC-MS and analyzed with respect to adult age, mating status, and diet. The hydrocarbons range in carbon number from C(21) to C(45) and consist of a homologous series of n-alkanes, 11-, 13-, and 15-methyl alkanes, 13,17-dimethyl alkanes, and Z-5, Z-7, and Z-9-alkenes. The wax esters found in the cuticular lipid fraction are a series of homologous compounds with the acid portion being short chain, unbranched, even carbon number acids from C(8) to C(20) (predominately C(8) to C(16)). The alcohol portions of the esters are secondary alcohols with carbon number from C(22) to C(25) (predominately C(23) and C(25)) with the hydroxyl function located at C(6), C(7), C(8), and C(9). Gender, age, and nutritional states were significant factors for variation in several of the individual esters, but mating status did not affect wax ester composition. Ontogenetic examinations indicated that prepupal, and early pupal cuticular lipids contain only hydrocarbons. Low levels of wax esters are detectable in late stage pupae, and somewhat greater quantities of wax esters are present on newly eclosed adults. When pharate adults emerge from the cocoon, however, their cuticular lipids consist of approximately equal amounts of hydrocarbons and wax esters, and 6d post emergence from the cocoon, wax esters are the predominant lipid component.

Age Factors↗
PubMed2006

Modelling the effects of alcohol ethoxylates on diffusion of pesticides in the cuticular wax of Chenopodium album leaves.

Cuticular waxes represent the first and, in most cases, the limiting barrier for foliar uptake of pesticides from solution. Sorption of pesticides in reconstituted cuticular wax (wax/water partition coefficients) of Chenopodium album L. and in isolated cuticular membranes (cuticle/water partition coefficients) of Prunus laurocerasus L. was determined. Diffusion coefficients of pesticides in reconstituted cuticular wax of C. album leaves were size-dependent, increasing with increasing molar volume. In the presence of alcohol ethoxylates, diffusion coefficients were enhanced by up to two orders of magnitude, and size selectivity was significantly decreased. The accelerating effect and the decrease in size selectivity were attributed to plasticisation of the cuticular wax by the alcohol ethoxylates increasing the fluidity in the wax. A free volume model adopted from polymer science was successfully applied to predict diffusion coefficients of pesticides on the basis of the transport properties of the wax (size selectivity and crystallinity), the molar volume of the diffusing compound and the accelerator concentration in the wax.

Chenopodium album↗
PubMed2005

Sorption in reconstituted waxes of homologous series of alcohol ethoxylates and n-alkyl esters and their effects on the mobility of 2,4-dichlorophenoxybutyric acid.

Equilibrium sorption of n-alkyl esters (dimethyl suberate, diethyl suberate, diethyl sebacate, dibutyl suberate and dibutyl sebacate) and monodisperse alcohol ethoxylates (diethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol and octaethylene glycol monododecyl ether) between the reconstituted cuticular waxes of Stephanotis floribunda Brongn (Madagascar jasmine) or Hordeum vulgare L (barley) leaves and an external aqueous receptor solution was determined. Logarithms of the wax/receptor partition coefficient (K(wax/rec)) of the n-alkyl esters increased linearly with the number of C-atoms. With alcohol ethoxylates, log K(wax/rec) decreased linearly with the number of ethylene oxide units. For both groups of compounds, K(wax/rec) increased with increasing lipophilicity. The values of K(wax/rec) in Stephanotis wax were between 5 and 16 times higher than in barley wax. It is argued that this difference was due to different chemical composition and crystallinity of the waxes. Mobility of [14C]2,4-dichlorophenoxybutyric acid (2,4-DB) in reconstituted Stephanotis and barley wax was increased by a factor of 2-8 by both n-alkyl esters and alcohol ethoxylates. Effects on the mobility of 2,4-DB were linearly related to the internal concentrations of n-alkyl esters and alcohol ethoxylates in reconstituted Stephanotis or barley wax. At the same internal concentrations the effect of n-alkyl esters on the mobility of 2,4-DB in wax exceeded that of alcohol ethoxylates by between 1 and 2 orders of magnitude. Results are discussed in relation to formulating systemic pesticides.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2001

[Wax model collection of the Department of Dermatology, University of Münster].

Between the 17th century and the middle of the 20th century, wax models were widely used for training in anatomy and other medical fields, especially dermatology. Thereafter, photographic techniques led to the replacement and subsequent dissolution of many European wax model collections. Unfortunately many wax models lose their original colors over time. Since only few mouleurs (wax artists) are still active in Europe conserving wax models, the "dying of moulages" cannot be stopped. Consequently, the existing wax models are of medical and historical interest since they reflect the development of our speciality. The Department of Dermatology in Münster is in the possession of 121 wax models, which are presented in this article.

Dermatology↗