Cuticular Layer Research Articles

A Silica Gel Based Method for Extracting Insect Surface Hydrocarbons

Here, we describe a novel method for the extraction of insect cuticular hydrocarbons using silica gel, herein referred to as "silica-rubbing". This method permits the selective sampling of external hydrocarbons from insect cuticle surfaces for subsequent analysis using gas chromatography-mass spectrometry (GC-MS). The cuticular hydrocarbons are first adsorbed to silica gel particles by rubbing the cuticle of insect specimens with the materials, and then are subsequently eluted using organic solvents. We compared the cuticular hydrocarbon profiles that resulted from extractions using silica-rubbing and solvent-soaking methods in four ant and one bee species: Linepithema humile, Azteca instabilis, Camponotus floridanus, Pogonomyrmex barbatus (Hymenoptera: Formicidae), and Euglossa dilemma (Hymenoptera: Apidae). We also compared the hydrocarbon profiles of Euglossa dilemma obtained via silica-rubbing and solid phase microextraction (SPME). Comparison of hydrocarbon profiles obtained by different extraction methods indicates that silica rubbing selectively extracts the hydrocarbons that are present on the surface of the cuticular wax layer, without extracting hydrocarbons from internal glands and tissues. Due to its surface specificity, efficiency, and low cost, this new method may be useful for studying the biology of insect cuticular hydrocarbons.

Scanning Electron Microscopic Characterization and Elemental Analysis of Hair: A Tool in Identification of Felidae Animals

Within the forensic identification the study of animal hair has remain limited to cross-species comparisons from the same family but there is also considerable changes in those animals like scale layer differentiation growth pattern, tensile strength, granulation and elemental profile of the animal hair. Here a rapid method is described for assessing a variety of morphological characteristics for identification of species that could be easily used by forensic investigators to identify the hairs from different species by just a fraction of single hair sample using Scanning Electron Microscope (SEM). Hair samples from 90 animals of Felidae family, 30 from each Panthera leo persica (lion), Panthera paradus fusca (Leopard) and Panthera tigris tigris (Tiger) were examined for their cuticular scale layer difference pattern and measurements were taken using SEM annotations. Significant differences were observed in scale layer pattern differences/difference in overlapping of each scale in hair which can be used in identification of the species. The difference between each layer was observed as 6.72431 ± 0.4, 7.869655 ± 0.38 and 9.592897 ± 0.5 μm for Panthera Leo persica, Panthera tigris tigris and Panthera pradus fusca. Elemental analysis for all the three species from Felidae family have been evaluated using Energy Dispersive Spectrum coupled with SEM for analysis of Sodium, Potassium, Calcium and Sulfur. Significant results were obtained are can be further used to establish a concordance with the species identification.

Neurodegeneration of Drosophila drop‐dead mutants is associated with hypoxia in the brain

The Drosophila drop-dead (drd) mutant undergoes massive brain degeneration, resulting in sudden death. drd encodes a multi-pass membrane protein possessing nose resistant to fluoxetine (NRF) and putative acyltransferase domains. However, the etiology of brain degeneration that occurs in drd mutant flies is still poorly understood. Herein, we show that drd neurodegeneration may be because of an oxygen deficit in the brain. We found that DRD protein is selectively expressed in cells secreting cuticular and eggshell layers. These layers exhibit blue fluorescence upon UV excitation, which is reduced in drd flies. The drd tracheal air sacs lacking blue fluorescence collapse, which likely contributes to hypoxia. Consistently, genes induced in hypoxia are up-regulated in drd flies. Feeding of anti-reactive oxygen species agents partially rescue the drd from sudden death. We propose that drd flies can provide a non-invasive animal model for hypoxia-induced cell death.

Effect of atmospheric pressure helium plasma on felting and low temperature dyeing of wool

AbstractWool fabrics were treated with atmospheric pressure helium glow discharge plasma in an attempt to improve felting and dyeing behavior with cold brand reactive dyes using cold pad‐batch method at neutral pH. On glow plasma treatment, the hydrophilicity of wool surface and its resistance toward felting was greatly improved without any significant damage to the cuticle layer. The color strength of the plasma treated dyed wool on the surface (in terms of K/S) was found to be nearly double of the color strength of dyed untreated wool fabric. However, the corresponding total dye uptake of the treated wool increased by a much lower value of 40%–50%. The reason behind this altered dyeing behavior was investigated by studying the dye kinetics using infinite bath and surface characteristics using SEM and SIMS. It was found that the glow plasma treatment greatly transformed the chemical surface of the wool fibers. It resulted in uniform removal of hydrophobic cuticular layer, which resulted in better diffusion of the dye molecules into the fiber, and formation of hydrophilic NH2 groups near the surface, which helped in anchoring the dye molecules close to the surface giving higher color strength than expected. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

New plant taxa from the Lower Devonian (Lochkovian) of the Welsh Borderland, with a hypothesis on the relationship between hilate and trilete spore producers

A detailed investigation of charcoalified Lochkovian mesofossils, undertaken to circumscribe diversity and disparity in early land vegetation, has revealed a number of discoidal spore masses, enveloped by a featureless cuticular layer. The specimens are interpreted as incompletely preserved terminal sporangia. Based on haptotypic features of the spores, two groups of sporangia are recognised: the first contains alete sculptured monads, the separated products of dyads that are assigned to the dispersed cryptospore genus Cymbohilates Richardson; the second contains laevigate and apiculate trilete monads, the products of tetrads that are assigned to the dispersed genera Ambitisporites Hoffmeister, Streelispora (Chaloner and Streel) Richardson and Lister, and Aneurospora Streel. A new genus, Lenticulatheca, with four new species, L. magna, L. mesodeca, L. variabilis, and L. allenii, has been erected for the cryptospore producers, distinction being based on species and varieties of Cymbohilates. The trilete spore producers, which were far more numerous, have been assigned to a second new genus, Paracooksonia, to emphasise similarities with Cooksonia Lang, both in gross morphology of the spore mass and in situ spore genera. Paracooksonia apiculispora is erected for specimens with in situ apiculate spores and Paracooksonia ambitispora is erected for laevigate in situ spores. Similarities in the bilayered exospore and sculpture, together with those of gross morphology have led to the hypothesis that the two new genera are closely related, the major distinction arising from changes in the timing of cytokinesis during meiosis that resulted in either dyads or tetrads. Information on missing vegetative features is essential to elucidating unequivocally the proximity to the tracheophytes, but similarities with the Cooksonia complex suggest that the two new genera should be considered rhyniophytoids.

New Insights into the Properties of Pubescent Surfaces: Peach Fruit as a Model

The surface of peach (Prunus persica 'Calrico') is covered by a dense indumentum, which may serve various protective purposes. With the aim of relating structure to function, the chemical composition, morphology, and hydrophobicity of the peach skin was assessed as a model for a pubescent plant surface. Distinct physicochemical features were observed for trichomes versus isolated cuticles. Peach cuticles were composed of 53% cutan, 27% waxes, 23% cutin, and 1% hydroxycinnamic acid derivatives (mainly ferulic and p-coumaric acids). Trichomes were covered by a thin cuticular layer containing 15% waxes and 19% cutin and were filled by polysaccharide material (63%) containing hydroxycinnamic acid derivatives and flavonoids. The surface free energy, polarity, and work of adhesion of intact and shaved peach surfaces were calculated from contact angle measurements of water, glycerol, and diiodomethane. The removal of the trichomes from the surface increased polarity from 3.8% (intact surface) to 23.6% and decreased the total surface free energy chiefly due to a decrease on its nonpolar component. The extraction of waxes and the removal of trichomes led to higher fruit dehydration rates. However, trichomes were found to have a higher water sorption capacity as compared with isolated cuticles. The results show that the peach surface is composed of two different materials that establish a polarity gradient: the trichome network, which has a higher surface free energy and a higher dispersive component, and the cuticle underneath, which has a lower surface free energy and higher surface polarity. The significance of the data concerning water-plant surface interactions is discussed within a physiological context.

SHINE transcription factors act redundantly to pattern the archetypal surface of Arabidopsis flower organs.

Floral organs display tremendous variation in their exterior that is essential for organogenesis and the interaction with the environment. This diversity in surface characteristics is largely dependent on the composition and structure of their coating cuticular layer. To date, mechanisms of flower organ initiation and identity have been studied extensively, while little is known regarding the regulation of flower organs surface formation, cuticle composition, and its developmental significance. Using a synthetic microRNA approach to simultaneously silence the three SHINE (SHN) clade members, we revealed that these transcription factors act redundantly to shape the surface and morphology of Arabidopsis flowers. It appears that SHNs regulate floral organs' epidermal cell elongation and decoration with nanoridges, particularly in petals. Reduced activity of SHN transcription factors results in floral organs' fusion and earlier abscission that is accompanied by a decrease in cutin load and modified cell wall properties. SHN transcription factors possess target genes within four cutin- and suberin-associated protein families including, CYP86A cytochrome P450s, fatty acyl-CoA reductases, GSDL-motif lipases, and BODYGUARD1-like proteins. The results suggest that alongside controlling cuticular lipids metabolism, SHNs act to modify the epidermis cell wall through altering pectin metabolism and structural proteins. We also provide evidence that surface formation in petals and other floral organs during their growth and elongation or in abscission and dehiscence through SHNs is partially mediated by gibberellin and the DELLA signaling cascade. This study therefore demonstrates the need for a defined composition and structure of the cuticle and cell wall in order to form the archetypal features of floral organs surfaces and control their cell-to-cell separation processes. Furthermore, it will promote future investigation into the relation between the regulation of organ surface patterning and the broader control of flower development and biological functions.

Distribution of mechanoreceptive sensilla and their functions in the defensive behavior of tenebrionid beetle pupae

correspondence: Toshio Ichikawa Department of Biology, Faculty of sciences, Kyushu University, Fukuoka 812-8581, Japan Tel +81 92 642 2612 Fax +81 92 642 2315 email tichiscb@kyuhsu-u.org Background: Pupae of the tenebrionid beetles exhibit different defensive behaviors in response to tactile stimulation of different parts of their bodies. Little is known about the mechanosensory mechanisms that initiate these defensive behaviors. To understand the mechanisms, we examined the distribution and function of the mechanoreceptive sensilla on the pupal body of Zophobas atratus. Methods: The sensilla on the surface of the pupal cuticle were observed using light and scanning electron microscopy. The tactile sensitivity of various parts of the pupal body was tested using three probes with different bending forces. The function of particular sensilla was examined by stimulating them electrically. Results: Hair (trichoid) sensilla were classified according to their length, ie, long hair sensilla (80–200 μm) were mostly located on the lateral regions of each body segment and short hairs (5–50 μm) were distributed across almost the entire surface of the pupal body, except for the elytra and intersegmental membrane of the abdomen. In addition to the trichoid sensilla, almost all parts of the pupal body, including the elytra and the intersegmental membrane, had campaniform sensilla (CS) with a dome-like structure in the cuticular layer; these sensilla detected strains in the cuticle. The CS were concentrated on the articulation of segmented appendages and the lateral region of the intersegmental membrane. The defensive response (abdominal rotation) to electrical stimulation was greatly reduced when afferent nerves from CS clustered on the apical region of the tarsus were transected. Conclusion: CS may be responsible for the high sensitivity of pupal appendages to tactile stimuli. The CS located on the appendages and abdominal intersegmental membrane may trigger specific and effective defensive behaviors. Both types of mechanoreceptive sensilla may enable pupal perception of the external environment, including the location of potentially harmful stimuli, and are involved in the control of defensive posture and movement.

A member of the PLEIOTROPIC DRUG RESISTANCE family of ATP binding cassette transporters is required for the formation of a functional cuticle in Arabidopsis.

Although the multilayered structure of the plant cuticle was discovered many years ago, the molecular basis of its formation and the functional relevance of the layers are not understood. Here, we present the permeable cuticle1 (pec1) mutant of Arabidopsis thaliana, which displays features associated with a highly permeable cuticle in several organs. In pec1 flowers, typical cutin monomers, such as ω-hydroxylated fatty acids and 10,16-dihydroxypalmitate, are reduced to 40% of wild-type levels and are accompanied by the appearance of lipidic inclusions within the epidermal cell. The cuticular layer of the cell wall, rather than the cuticle proper, is structurally altered in pec1 petals. Therefore, a significant role for the formation of the diffusion barrier in petals can be attributed to this layer. Thus, pec1 defines a new class of mutants. The phenotypes of the pec1 mutant are caused by the knockout of ATP BINDING CASSETTEG32 (ABCG32), an ABC transporter from the PLEIOTROPIC DRUG RESISTANCE family that is localized at the plasma membrane of epidermal cells in a polar manner toward the surface of the organs. Our results suggest that ABCG32 is involved in the formation of the cuticular layer of the cell wall, most likely by exporting particular cutin precursors from the epidermal cell.

Congruence of epicuticular hydrocarbons and tarsal secretions as a principle in beetles

Within beetles, those species that are adapted to life on plants have developed widened tarsi with specialised hairy attachment structures. The capability to adhere to smooth surfaces is based on a liquid film on the surface of these structures, the composition of which is similar to the cuticular lipids. By means of a cluster analysis based on chemical similarities between samples obtained from tarsi or elytra of 35 species using solid phase microextraction, the present study strongly suggests that this chemical congruence is a principle in beetles. This supports the idea of tarsal liquids being part of the cuticular lipid layer and contributes to the understanding of liquid-mediated attachment systems.

Water as a major modulator of the mechanical properties of insect cuticle

The mechanical properties of the sternal cuticle of the locust were investigated by nanoindentation. Modulus and hardness of the exo-, meso-, and endocuticular layers were locally measured under dry and fully wetted conditions in the normal (i.e. perpendicular to the outer surface) as well as in the transverse direction (i.e. parallel to the alignment of the respective layers). The results show that water has a major impact on the mechanical properties of all layers. After drying the endocuticle, in particular, became harder by a factor of up to 9 and stiffer by a factor of up to 7.4. Additionally the gradual decrease in hardness and Young’s modulus from the outer exo- to the inner endocuticle, characteristic of native cuticle, was eliminated or even reversed in dried cuticle. A pronounced anisotropy was revealed in all layers when comparing data obtained by probing in the normal (lower values) vs. probing in the transverse direction (higher values). Cyclic drying and rewetting of the endocuticle showed that the mechanical properties can be reproducibly changed by altering the water content. Based on our results we propose a new role of the epicuticle: fine-tuning of the mechanical properties of the different cuticular layers can be accomplished by setting the local cuticular transpiration.

A hundred-year-old question: is the moss calyptra covered by a cuticle? A case study of Funaria hygrometrica.

The maternal gametophytic calyptra is critical for moss sporophyte development and ultimately sporogenesis. The calyptra has been predicted to protect the sporophyte apex, including the undifferentiated sporogenous region and seta meristem, from desiccation. We investigate the hypothesis that this waterproofing ability is due to a waxy cuticle. The idea that moss calyptrae are covered by a cuticle has been present in the literature for over a century, but, until now, neither the presence nor the absence of a cuticle has been documented for any calyptra. The epidermis of the calyptra, leafy gametophyte and sporophyte sporangia of the moss Funaria hygrometrica were examined using scanning and transmission electron microscopy. Thicknesses of individual cuticle layers were quantified and compared statistically. The immunochemistry antibody (LM19) specific for pectins was used to locate cell wall material within the cuticle. A multi-layered cuticle is present on the calyptra of F. hygrometrica, including layers analogous to the cuticular layer, cell wall projections, electron-lucent and electron-dense cuticle proper observed in vascular plants. The calyptra rostrum has a cuticle that is significantly thicker than the other tissues examined and differs by specialized thickenings of the cuticular layer (cuticular pegs) at the regions of the anticlinal cell walls. This is the first documentation of cuticular pegs in a moss. The calyptra and its associated cuticle represent a unique form of maternal care in embryophytes. This organ has the potential to play a critical role in preventing desiccation of immature sporophytes and thereby may have been essential for the evolution of the moss sporophyte.

Asymptomatic cysticercosis in wistar albino rats: A note of caution to all biomedical researchers

Sir, Rat is one of the most commonly used animals in biomedical research. It can spread various types of zoonotic diseases, most commonly, rat fever (caused by Streptobacillus moniliformis), ring worm infestation, rabies, tetanus, and salmonella.[1] Hence it is important to have a thorough knowledge regarding the common zoonotic diseases transmitted by the animal, the common modes of transmission to humans as well as necessary precautionary methods during handling of the animals. The researcher should not only keep in mind the possible zoonotic diseases that can affect him, but also the asymptomatic parasitic diseases common to the animals that can erroneously affect the results of the experiments. In our setting, we conducted an experiment involving Wistar albino rats, maintained according to the Committee for the Purpose of Control and Supervision on Experiments on Animals (CPCSEA) guidelines to observe the effects of fluoxetine on rat endometrium. At the end of the study, after sacrificing the animals, one of the rats of the control group (treated only with oral 0.9% normal saline) showed cyst formation on the liver. Histopathological examination confirmed the cyst to be of cestode origin as evidenced by the presence of an outer acellular eosinophilic cuticular layer and underlying subtentacular layer along with scolex-containing hooks and suckers [Figure 1]. Some giant cell reaction along with signs of inflammation was also evident in the adjoining tissue. Figure 1 HP examination shows outer acellular eosinophilic cuticular layer, subtentacular layer along with scolex containing hooks and suckers at 100× magnification Molecular techniques like PCR-linked mitochondrial DNA sequencing were not used to confirm the species of the tapeworm larva. But it is most likely due to the encysted larval form of Taenia taeniaeformis, i.e. Cysticercus fasciolaris, as it is one of the most common cestodes affecting the livers of the rats. Sometimes it has been found to be associated with hepatic fibrosarcomas.[2,3] Hence, animal experiments which particularly involve testing of liver functions can have erroneous results if asymptomatic rats harboring C. fasciolaris are used. Although our experimental protocol did not require measurements of liver function, it most likely did not affect the outcome. Besides Wistar albino rats, other commonly used laboratory animals can have asymptomatic parasitic infestations that can act as a restricting factor for attainment of experimental protocol. Therefore, the biomedical researchers should be aware of the asymptomatic spontaneous lesions to correctly interpret the outcome of their experiments.

Cerebral coenurosis mimicking hydatid disease – report of two cases from South India

Coenurosis, a rare zoonotic disease caused by the larval form of Taenia multiceps (bladderworm) is common in sheep rearing countries, but human infections are rare. Central nervous system involvement produces large giant sized cysts that radiologically closely mimic hydatid cysts. Most human infections resulting in cerebral coenuri have been reported from Europe and Africa. We report two cases of cerebral coenurosis from India, the first in a 55-year-old male presenting with a large cystic lesion in the right parietooccipital region and the second occurring in a 36-year-old male involving the left temporal trigonal region, that radiologically closely mimicked hydatid cyst. Histopathologic examination revealed characteristic features of coenuri with multiple protoscolices invaginating into a large cyst lined by outer cuticular layer. Awareness of this rare parasitic infestation is important to discriminate from the more common hydatid and giant cysticercal cysts.

Morphological organization of the dorsal protuberance of Linepithema humile (Mayr, 1868) ant's larvae (Hymenoptera, Formicidae)

The Argentine ant Linepithema humile is an important invasive species because of the levels of infestation that it can reach; however, there is little information about its presence, histological organization, and function of the dorsal protuberance, which is found exclusively in their larvae. The objective of this study was to describe it in L. humile through scanning electron microscopy and transmission electron microscopy, bringing information about this structure. The epidermis of these larvae have cuticles covering the whole body, and is formed by a sequence of overlapping lamellas where the inner ones were thicker and presented lower electron density, whereas the outer ones were thinner and highly electron dense. Pores or pore-like channels were not observed. A thick and acellular region composed of granular material was found under the cuticular layer. Out of this region, the flattened epidermic cells formed an epithelial layer. For the dorsal protuberance region, these cells become prismatic, and similarly to the cuticle, presents significant thickening. These cells presented extended microvilli, as well as a great amount of lamellar rough endoplasmic reticulum. Under this epithelium was observed a concentration of fat body cells, more numerous in the dorsal protuberance region. This study indicated that the dorsal protuberance present in the first segment of L. humile larvae has apparently no secretory function because no pores were found. This fact allowed to conclude that in L. humile larvae the dorsal protuberance would have the function to make it easier for the worker ants to carry them within the colony.

Leaf anatomy and micromorphology of six Posoqueria Aublet species (Rubiaceae)

Abstract The present study deals with the leaf anatomy and leaf surface of Posoqueria acutifolia Mart., P. latifolia Mart., P. longiflora Aublet, P. macropus Mart., P. palustris (Rudge) Roem. and Posoqueria sp., collected in fragments of Atlantic rain forest, Rio de Janeiro, Brazil. The epicuticular wax may occur in the form of filaments, granules or crusts. The leaves are covered by a thick cuticular layer that may be smooth or striated. Paracytic stomata, and non-glandular trichomes are limited to the abaxial surface; the latter are numerous in P. palustris, and rare in P. longiflora and P. latifolia. Leaves have a dorsiventral structure, with only one layer of palisade parenchyma and varied amounts of spongy parenchyma. Idioblasts containing crystalliferous sand were observed, and were more abundant in P. latifolia. The leaf blade vascular system is formed by collateral bundles with a parenchymatous sheath, associated with fibers. The vascular system of the petiole and the leaf blade forms an arch. Some of the anatomical features observed can be used to distinguish the species studied. Anatomical leaf characters could be used in the recognition of six species of Posoqueria studied, such as anticlinal wall of epidermal cells, wax deposition, trichomes and shape of the leaf margin.

Ultrastructural analysis of Wuchereria bancrofti (Nematoda: Filarioidea) body wall

Bancroftian filariasis constitutes the principal mosquito-borne nematode infection of humans and the surface of adult of Wuchereria bancrofti seems to be especially important in the intricate interplay between host and parasite. The study of the parasite's surface structure might help to understand the localization and function of various organelles. W. bancrofti adult worms were recovered from untreated patients during hydrocele repair surgery and studied by transmission electron microscopy. The body wall of adult parasite is composed of cuticle, hypodermis and muscular layer. Cuticle is the external layer and shows transverse cuticular striation. It is composed by an epicuticle, cortical layers, median layer, fibrous layers and basal layer. The epicuticle is the most external cuticular layer and appears as a single laminar electron-dense layer. The cortical external region is more electron-dense and granular in appearance than the inner cortical layer. Electron-dense structures, called bosses are randomly distributed filling the cuticular striation. The median layer is formed by an electron-dense and continuous thick line. The fibrous layer is subdivided in inner and external layers connected by projections. The basal layer includes a large quantity of membranous projections directed toward the hypodermis. The hypodermis is a syncytium where some cellular organelles are observed. The somatic musculature is meromyarian. The muscle fibers consist of contractile and non-contractile regions and the contractile region is composed of myofilaments separated by dense body. This is the first study of W. bancrofti adult worms obtained from untreated patients and studied by transmission electron microscopy.

Reluctant hydrocephalus

Reluctant hydrocephalus

Plant surfaces of vegetable crops mediate interactions between chemical footprints of true bugs and their egg parasitoids

During the host location process, egg parasitoids can eavesdrop on chemical cues released from immature and adult hosts. These indirect host-related cues are highly detectable, but of low reliability because they lead egg parasitoid females to an area where oviposition is likely to occur rather then providing wasps with direct information on the presence of eggs and their location. In the host-parasitoid associations between true bugs and their scelionid egg parasitoids, female wasps perceive the chemical residues left by host adults walking on substrates as contact kairomones, displaying a characteristic arrestment posture. In this study, we demonstrated that epicuticular waxes of leaves of two vegetable crops, broad bean, Vicia faba, and collard greens, Brassica oleracea, mediate the foraging behavior of Trissolcus basalis (Wollaston) by adsorbing contact kairomones from adults of Nezara viridula (L.). Trissolcus basalis females showed no response when released on the adaxial leaf surface of broad bean or collard green plants with intact cuticular wax layers that had not been exposed to bugs, whereas wasps displayed the arrestment posture when intact leaves were contaminated by chemical residues from host females. Adaxial leaf surfaces that were dewaxed with an aqueous solution of gum arabic and afterwards contaminated by N. viridula females elicited no arrestment responses from wasp females. Similarly, leaves contaminated by host females and subsequently dewaxed did not elicit responses from female wasps. These findings reveal the important role of plant waxes in N. viridula - T. basalis semiochemical communication.

Fruit-Surface Flavonoid Accumulation in Tomato Is Controlled by a SlMYB12-Regulated Transcriptional Network

The cuticle covering plants' aerial surfaces is a unique structure that plays a key role in organ development and protection against diverse stress conditions. A detailed analysis of the tomato colorless-peel y mutant was carried out in the framework of studying the outer surface of reproductive organs. The y mutant peel lacks the yellow flavonoid pigment naringenin chalcone, which has been suggested to influence the characteristics and function of the cuticular layer. Large-scale metabolic and transcript profiling revealed broad effects on both primary and secondary metabolism, related mostly to the biosynthesis of phenylpropanoids, particularly flavonoids. These were not restricted to the fruit or to a specific stage of its development and indicated that the y mutant phenotype is due to a mutation in a regulatory gene. Indeed, expression analyses specified three R2R3-MYB–type transcription factors that were significantly down-regulated in the y mutant fruit peel. One of these, SlMYB12, was mapped to the genomic region on tomato chromosome 1 previously shown to harbor the y mutation. Identification of an additional mutant allele that co-segregates with the colorless-peel trait, specific down-regulation of SlMYB12 and rescue of the y phenotype by overexpression of SlMYB12 on the mutant background, confirmed that a lesion in this regulator underlies the y phenotype. Hence, this work provides novel insight to the study of fleshy fruit cuticular structure and paves the way for the elucidation of the regulatory network that controls flavonoid accumulation in tomato fruit cuticle.