云南腾冲上新统芒棒组植物分散角质层研究

在云南腾冲上新统芒棒组中发现保存较好的植物分散角质层,共识别出7种:Reticutissolida,Reticutis tylotis,Fundicutis verriculis,Lusaticutis arizelis,Piliparicutis anfracta,Discrepoparicutis elongata,Enormicutis torquata,可归于6属,4亚类,4类,1个大类,表现出上叶角质层类型和下叶角质层类型的组合特征及上叶角质层类型的优先保存情况。从表皮细胞形态及气孔器等微观特征上看,具气孔的4种之间有着明显的差别,表明它们可能分别来自不同的母体植物;其中3种角质层的母体植物极有可能为被子植物,并处于优势地位。滇西当时温暖湿润的热带-亚热带、暖温带气候,为分散角质层的母体植物提供了良好的生存条件。而该区植物分散角质层的发现为分析其母体植物和重建古环境提供微体植物化石证据。     

Consideration of the importance of hydrophobic interactions in stabilizing insect cuticle

Protein fractions of insect cuticles with different mechanical properties have related values of polarity and hydrophobicity. Hydrophobicity is important for the self-assembly of cuticle which is produced prior to the moult and in plasticization of cuticle. The cuticles of soft-bodied fly larvae are quite distinct from those of exopterygotes (e.g. locusts) and this can be related to the chemistry and mode of tanning. The properties of cuticular proteins are compared: the proteins of the pliant cuticles most closely resemble globulins, and the proteins in stiff cuticles are more like fibrous and hydrophobic structural proteins. Changes in the environment of the proteins may alter their shape and hence the mechanical properties of the cuticle.     

Cuticular Collagenous Proteins of Second-stage Juveniles and Adult Females of Meloidogyne incognita: Isolation and Partial Characterization

Cuticles isolated from second-stage juveniles and adult females of Meloidogyne incognita were purified by treatment with 1% sodium dodecyl sulfate (SDS). The juvenile cuticle was composed of three zones differing in their solubility in β-mercaptoethanol (BME). Proteins in the cortical and median zones were partially soluble in BME, whereas the basal zone was the least soluble. The BME-soluble proteins from the juvenile cuticle were separated into 12 bands by SDS-polyacrylamide gel electrophoresis and characterized as collagenous proteins based on their sensitivity to collagenase and amino acid composition. The adult cuticle consisted of two zones which were dissolved extensively by BME. The basal zone was completely solubilized, leaving behind a network of fibers corresponding to the cortical zone. The BME-soluble proteins from the adult cuticle were separated by electrophoresis into nine bands one of which constituted > 55% of the total BME-soluble proteins. All bands were characterized as collagenous proteins. Collagenous proteins from juvenile cuticles also contained glycoproteins which were absent from the adult cuticles.     

Sun and shade leaves? Cuticle ultrastructure of Jurassic Komlopteris nordenskioeldii (Nathorst) Barbacka

An ultrastructural transmission electron microscope (TEM) study of fossil leaf cuticles from the Jurassic pteridosperm Komlopteris nordenskioeldii (Nathorst) Barbacka from the Mecsek Mountains (South Hungary) was conducted. Remnants of cuticles of leaves originating from so-called "sun and shade" environments were sectioned with a diamond knife, transversally as well as longitudinally. Although the present study showed a simple type of cuticle in this pteridosperm, differences were observed in the occurrence of its components, such as electron lucent amorphous material and various densities of granules, which give rise to different zones. The included fibrilous elements appeared to be made of aggregated and aligned granules, equivalent in size and electron density to nearby non-fibrilous granular regions. The combinations of these ultrastructural features allow distinctions between four types of cuticle: sun upper, sun lower, shade upper and shade lower. Considering the distinction made earlier in two types of cuticle and supposed to be related to sun and shade on the basis of macroscopical and microscopical features, four types only on the basis of differences in thickness, the present study reinforces the distinctions with ultrastructural microcharacteristics. As this study shows the variations in ultrastructure of cuticle among the four types, the differences observed may reveal the great sensitivity of some plants to environment. At the same time, it points out the importance, in ultrastructural studies of cuticles, of studying a number of samples for one taxon.     

Trilobite cuticle thickness in relation to palaeoenvironment

100 thickness measurements from thin sections of cephala or pygidia of early Ordovician trilobites occurring across an onshore to offshore environmental gradient show that progressively greater maximum cuticle thickness was characteristic of increasingly inshore sites. There is a 40-fold difference between the thinnest and thickest cuticles, and exclusively thin cuticles are confined to the offshore Olenid Biofacies. Variability in cuticle thickness increases offshore to onshore. Environmental control is shown to be more influential on cuticle thickness than is the overall length of the trilobite: some comparatively large trilobites having thin cuticles and small trilobites thick cuticles. The environmental factors which might be responsible for the pattern are briefly discussed. The thin cuticles dominating the offshore Olenid Biofacies were probably appropriate for dysaerobic conditions. Thick cuticles in the most inshore biofacies may have offered protection against predators and turbulence, but the additional presence there of trilobites with thinner cuticles is considered to reflect the greater heterogeneity of the epeiric habitat.     

Overlapping stage-specific sets of numerous small collagenous polypeptides are translated in vitro from Caenorhabditis elegans RNA

Caenorhabditis elegans synthesizes four morphologically distinct types of collagenous cuticles during its lifetime. We show that in RNA populations isolated early or late during the L4-to-adult molt, chick and nematode collagen DNAs hybridize strongly to RNAs of about 1.2 kb. Different but overlapping classes of correspondingly small collagenous polypeptides (310-460 residues in length) are translated in vitro from these two populations and from RNA isolated at the L2-to-dauer molt. Over 60 different collagenous translation products are identified. These collagenous polypeptides are smaller than mature cuticle collagens and smaller than most vertebrate collagens. They probably represent cuticle collagen precursors and the primary products of the cuticle collagen genes of C. elegans.     

The cuticle of Caenorhabditis elegans. II. Stage-specific changes in ultrastructure and protein composition during postembryonic development

The cuticle of the free-living nematode Caenorhabditis elegans is a proteinaceous extracellular structure that is replaced at each of four postembryonic molts by the underlying hypodermis. The cuticles of the adult and three juvenile stages (L1, Dauer larva, L4) have been compared ultrastructurally and biochemically. Each cuticle has an annulated surface and comprises two main layers, an inner basal layer and an outer cortical layer. The adult cuticle has an additional clear layer which separates the basal and cortical layers and is traversed by regularly arranged columns of electron-dense material. The fine structure of the cortical layer is similar in cuticles from different stages while that of the basal layer is stage specific. Purified cuticles were obtained by sonication and treatment with sodium dodecyl sulfate (SDS) and their component proteins solubilized with a sulfhydryl reducing agent. The degree of cuticle solubility is stage specific and the insoluble structures for each cuticle were localized by electron microscopy. Analysis of ³⁵S-labeled soluble cuticle proteins by SDS-polyacrylamide gel electrophoresis yields unique banding patterns for each stage. Most proteins are of high molecular weight (100–200 K) and are restricted to particular stages. Sixteen of the nineteen major proteins characterized are specifically degraded by bacterial collagenase. The results indicate that the different molts are not reiterative, but require the integration of both unique and shared gene functions. The potential use of stage-specific cuticle differences to identify and characterize regulatory genes controlling cuticle-type switching during development is discussed.     

Patterns of Effective Permeability of Leaf Cuticles to Acids

Plants in the field are frequently exposed to anthropogenic acid precipitation with pH values of 4 and below. For the acid to directly affect leaf tissues, it must pass through the leaf cuticle, but little is known about the permeability of cuticles to protons, or about the effect of different anions on this permeability. We investigated the movement of protons through isolated astomatous leaf cuticles of grapefruit (Citrus X paradisi Macfady.), rough lemon (Citrus limon [L.] Burm. fils cv Ponderosa), and pear (Pyrus communis L.) using hydrochloric, sulfuric, and nitric acids. Cuticles were enzymically isolated from leaves and placed in a diffusion apparatus with pH 4 acid on the morphological outer surface of the cuticle and degassed distilled water on the inner surface. Changes in pH of the solution on the inner surface were used to determine rates of effective permeability of the cuticles to the protons of these acids. Most cuticles exhibited an initial low permeability, lasting hours to days, then after a short transition displayed a significantly higher permeability, which persisted until equilibrium was approached. The change in effective permeability appears to be reversible. Effective permeabilities were higher for sulfuric acid than for the others. A model of the movement of protons through the cuticle is presented, proposing that dissociated acid groups in channels within the cutin are first protonated by the acid, accounting for the low initial effective permeability; then protons pass freely through the channels, resulting in a higher effective permeability.     

Cuticle characteristics and volatile emissions of petals in Antirrhinum majus

Floral volatiles, which are small and generally water-insoluble, must move from their intracellular sites of synthesis through the outermost cuticle membrane before release from the flower surface. To determine whether petal cuticle might influence volatile emissions, we performed the first analysis of petal cuticle development and its association with the emission of flower volatiles using Antirrhinum majus L. (snapdragon) as a model system. Petal cuticular wax amount and composition, cuticle thickness and ultrastructure, and the amounts of internal and emitted methylbenzoate (the major snapdragon floral scent compound) were examined during 12 days, from flower opening to senescence. Normal ( n -) alkanes were found to be the major wax class of snapdragon petals (29.0% to 34.3%) throughout the 12 days examined. Besides n -alkanes, snapdragon petals possessed significant amounts of methyl branched alkanes (23.6–27.8%) and hydroxy esters (12.0–14.0%). Hydroxy esters have not been previously reported in plants. Changes in amount of methylbenzoate inside the petals followed closely with levels of methylbenzoate emission, suggesting that snapdragon petal cuticle may provide little diffusive resistance to volatile emissions. Moreover, clear associations did not exist between methylbenzoate emission and the cuticle properties examined during development. Nevertheless, the unique wax composition of snapdragon petal cuticles shows similarities with those of other highly permeable cuticles, suggesting an adaptation that could permit rapid volatile emission by scented flowers.     

中国华夏植物区二叠纪几种科达植物分散角质层及其意义

中国华夏植物区科达植物的研究历史虽然最早可上溯至1883年,但直到1991年才首次报道其角质层构造。到目前为止,中国华夏植物区总共描述了4种科达植物原位角质层和3种分散角质层。但与欧美植物区相比,有关中国华夏植物区科达植物角质层的研究工作还较薄弱。本文较详细地描述了3种产自中国华夏植物区二叠纪煤系地层中的科达植物分散角质层。其中2种采自华北亚区南缘的安徽淮南新庄孜矿山西组A1煤顶板,地质时代为早二叠世;另一种采自华南亚区的贵州水城矿区大河边矿龙潭组顶部的11号煤层,地质时代为晚二叠世早期。将这3种科达植物分散角质层与已知的欧美植物区和中国华夏植物区的种类进行了对比,认为它们都是新的类型。讨论了这3种新的科达植物分散角质层所具有的古植物学意义。     

SCARABAEID BEETLE EXOCUTICLE AS AN OPTICAL ANALOGUE OF CHOLESTERIC LIQUID CRYSTALS

1. A review is given of the optical and architectural analogies between cholesteric liquid crystals and certain insect cuticles (Coleoptera: Scarabaeidae). Earlier observations on the optical properties (reflexion of circularly polarized light and high form optical rotation) are confirmed and extended. Both cholesteric liquid crystals and lamellate cuticle have helicoidal structure (Fig. i). Even though their chemistry and physical states are very different, we are justified in making the analogy, since their optical properties depend primarily on the pitch of their helicoidal architecture. 2. The unusual optical properties were located for the first time in the outer 5 to 20 μ of the exocuticle. This layer is transparent and has regular spacings in the range required for interference colours according to Bragg's law. Among Scarabaeid beetles which show interference colours, we distinguish two types of outer exocuticle. (i) Optically active cuticles which reflect circularly polarized interference colours; show high angles of form optical rotation in transmitted light; and anomalous form birefringence perpendicular to the cuticle surface (reversible by deproteinization). (2) Optically inactive cuticles which show none of the above properties and in which the form birefringence is parallel to the cuticle surface. In the electron microscope the ultrastructure of these two types of outer exocuticle is clearly different. 3. All of the optically active species reflect left hand circularly polarized light, irrespective of the wavelength of the reflected colour. They therefore appear dark when viewed through a right hand circular analyser. The sense of reflected circularly polarized light does not reverse at higher wavelengths as recorded by previous workers. (A simple treatment is given for combinations of various wavelengths with retardation plates of varying values, as used in circular analysers.) We confirm earlier reports that the sense of reflected circularly polarized light is of the opposite sense to the transmitted light. 4. Using monochromatic light we have measured the anomalous dispersion with wavelength of the magnitude of optical rotation for various optically active cuticles. The dispersion curves change from negative values at lower wavelengths to positive values at higher wavelengths, and cross the zero optical rotation axis at a wavelength (AQ) corresponding to the interference colour of each sample. There is reasonable agreement between A₀ and the interference colour calculated from ultrastructural evidence and by comparison with interference filters of known wavelength. A dispersion curve measured for a combined sample of two cuticles with different dispersion curves showed that the resultant is an algebraic summation of the two component curves. 5. We present the first experimental verification of existing mathematical treatments of anomalous form optical rotatory dispersion curves. Although these treatments were derived for cholesteric liquid crystals, they give a reasonable fit to our measured curves for cuticle. We have confirmed from our cuticle dispersion curves that a second zero value for optical rotation occurs at a wavelength higher than A₀, as predicted by the theory of Chandrasekhar and Rao (1968). This has not yet been observed in any cholesteric liquid crystal system. 6. Our evidence shows that in optically active cuticle, interference colour is determined by helicoid pitch. In Lomaptera interference coloration follows the bilateral symmetry of the insect. Hence helicoidal pitch is controlled in a bilaterally symmetrical manner. However, the sense of helicoid rotation is the same all over the beetle and is therefore bilaterally asymmetrical. This supports the view that helicoid pitch is under the local control of the epidermal cells which secrete the cuticle, whereas its sense of rotation may be determined by an extracellular self-assembly process. In view of the self-assembling properties of cholesteric liquid crystals, it is tempting to suggest that helicoidal cuticle could be formed by the stabilization of a liquid crystal. 7. We discuss in detail the differences between optically active and inactive cuticles. The constructive interference colours arising from both types are then briefly compared with other multiple layer reflecting systems in other animals. 8. A detailed comparison is made between the optics of cuticle and cholesteric liquid crystals. The optical analogy provides a two-way contact between cuticle biophysicists and liquid crystal physical chemists.     

中国华夏植物区二叠纪几种科达植物分散角质层及其意义

中国华夏植物区科达植物的研究历史虽然最早可上溯至1883年,但直到1991年才首次报道其角质层构造.到目前为止,中国华夏植物区总共描述了4种科达植物原位角质层和3种分散角质层.但与欧美植物区相比,有关中国华夏植物区科达植物角质层的研究工作还较薄弱.本文较详细地描述了3种产自中国华夏植物区二叠纪煤系地层中的科达植物分散角质层.其中2种采自华北亚区南缘的安徽淮南新庄孜矿山西组A1煤顶板,地质时代为早二叠世;另一种采自华南亚区的贵州水城矿区大河边矿龙潭组顶部的11号煤层,地质时代为晚二叠世早期.将这3种科达植物分散角质层与已知的欧美植物区和中国华夏植物区的种类进行了对比,认为它们都是新的类型.讨论了这3种新的科达植物分散角质层所具有的古植物学意义.     

Identification of an asparagine amidohydrolase from the filarial parasite Dirofilaria immitis

The nematode cuticle is a complex extracellular structure which is secreted by an underlying syncytium of hypodermal cells. Recent studies have demonstrated that the cuticle of parasitic nematodes is a dynamic structure with important absorptive, secretory, and enzymatic activities. In addition, the cuticle serves as a protective barrier against the host. A 48-h third stage larval Dirofilaria immitis cDNA library was immunoscreened with sera raised against larval cuticles. One clone, L3MC4 that reacted strongly with the anti-cuticle antisera was sequenced. The composite cDNA sequence comprises 2073 bp coding for a full-length protein of 590 amino acids. GenBank analysis showed that DiAsp had significant similarity to a Caenorhabditis elegans gene-product (54% identity) and to other asparaginases at the amino acid level. Escherichia coli-expressed recombinant DiAsp (rDiAsp) catalysed the hydrolysis of asparagine to aspartate and ammonia. Antibodies raised against D. immitis larval cuticles reacted with rDiAsp in immunoblots. This is the first report of identification of a cDNA clone encoding an asparaginase enzyme from a parasitic nematode.     

The presence of cutan limits the interpretation of cuticular chemistry and structure: Ficus elastica leaf as an example

Plant cuticles have been traditionally classified on the basis of their ultrastructure, with certain chemical composition assumptions. However, the nature of the plant cuticle may be misinterpreted in the prevailing model, which was established more than 150 years ago. Using the adaxial leaf cuticle of Ficus elastica, a study was conducted with the aim of analyzing cuticular ultrastructure, chemical composition and the potential relationship between structure and chemistry. Gradual chemical extractions and diverse analytical and microscopic techniques were performed on isolated leaf cuticles of two different stages of development (i.e. young and mature leaves). Evidence for the presence of cutan in F. elastica leaf cuticles has been gained after chemical treatments and tissue analysis by infrared spectroscopy and electron microscopy. Significant calcium, boron and silicon concentrations were also measured in the cuticle of this species. Such mineral elements which are often found in plant cell walls may play a structural role and their presence in isolated cuticles further supports the interpretation of the cuticle as the most external region of the epidermal cell wall. The complex and heterogeneous nature of the cuticle, and constraints associated with current analytical procedures may limit the chance for establishing a relationship between cuticle chemical composition and structure also in relation to organ ontogeny.     

Orestovia and the origin of vascular plants

The enigmatic Orestovia from the Lower Devonian of Siberia has a vascular cylinder of spiral and annular tracheids, external and internal cuticles in the cortex, and stomata. Abundant spores are occasionally preserved between the cortex cuticles. The 'reticulate structures' are thyriothecia of a hemisphaeriacean fungus. Spores of several types are found sticking to the cuticle. Orestovia can be conceived as a transitional form between the alga-like Protosalvinia and the sporangiate vascular plants. The origin of land plants is discussed.     

Investigations on epiphytic living Pseudomonas species from Malus domestica with an antagonistic effect to Venturia inaequalis on isolated plant cuticle membranes

In order to understand better the survival and mutual interaction of epiphytic bacteria and fungi on apple plants, bacteria collected from these plants were cultivated on intact adaxial, stoma free cuticle membranes originally obtained from apple. The bacteria were labelled with luciferase genes from Vibrio harveyi in order to follow up their development and activity on the isolated cuticles. Our finding was that the epiphytic bacteria can have access to nutrients below the cuticle without causing damage to these cuticular membranes. Bacterial proteins may enable this nutrient mobilization and we found, indeed, that more than 46 proteins that must have been delivered by the bacteria in response to interaction with the cuticles as they could be found below the cuticle membrane. Eight major representatives of this group of external proteins have been sequenced with electron spray quadrupole time of flight mass spectrometry and subsequently identified by data base homology search as a flagellin, a porin type protein and proteins that are involved in amino acid recruitment and metabolism.     

Is beta-pleated sheet the molecular conformation which dictates formation of helicoidal cuticle?

Over 100 sequences for cuticular proteins are now available, but there have been no formal analyses of how these sequences might contribute to the helicoidal architecture of cuticle or to the interaction of these proteins with chitin. A secondary structure prediction scheme (Hamodrakas, S.J., 1988. A protein secondary structure prediction scheme for the IBM PC and compatibles. CABIOS 4, 473-477) that combines six different algorithms predicting alpha-helix, beta-strands and beta-turn/loops/coil has been used to predict the secondary structure of chorion proteins and experimental confirmation has established its utility (Hamodrakas, S.J., 1992. Molecular architecture of helicoidal proteinaceous eggshells. In: Case, S.T. (Ed.), Results and Problems in Cell Differentiation, Vol. 19, Berlin-Heidelberg, Springer Verlag, pp. 116-186 and references therein). We have used this same scheme with eight cuticular protein sequences associated with hard cuticles and nineteen from soft cuticles. Secondary structure predictions were restricted to a conserved 68 amino acid region that begins with a preponderance of hydrophilic residues and ends with a 33 amino acid consensus region, first identified by Rebers and Riddiford (Rebers, J.F., Riddiford, L.M., 1988. Structure and expression of a Manduca sexta larval cuticle gene homologous to Drosophila cuticle genes. J. Mol. Biol. 203, 411-423). Both classes of sequences showed a preponderance of beta-pleated sheet, with four distinct strands in the proteins from 'hard' cuticles and three from 'soft'. In both cases, tyrosine and phenylalanine were found on one face within a sheet, an optimal location for interaction with chitin. We propose that this beta-sheet dictates formation of helicoidal cuticle.     

Attachment and germination of Entomophaga maimaiga conidia on host and non-host larval cuticle

The lepidopteran-specific fungal pathogen Entomophaga maimaiga is highly virulent against Lymantria dispar (gypsy moth) larvae, and other members of the family Lymantriidae. Numerous species in the subfamily Cuculliinae (Family Noctuidae) are not susceptible to E. maimaiga due to the inability of this fungus to penetrate the larval cuticle. Conidial attachment and germination were compared among five cuculliine species and L. dispar using bioassays and scanning electron microscopy. Although conidia were showered evenly across larvae during bioassays, on L. dispar conidia were most abundant on segments, where they adhered well to the cuticle and germinated at high percentages. Conidia on cuculliine cuticles were predominantly found in large, loose aggregations in intersegmental areas. Few conidia on cuculliine cuticle germinated and scanning electron microscopy revealed a thick film of mucous enveloping conidia. We hypothesize that the conidia on cuculliines become coated by this film and were only loosely attached to the larval cuticle. No such film was seen on L. dispar larvae where individual conidia appeared well attached. On L. dispar larvae many conidia also adhered to setae. To determine if hydrophobicity affected the ability of E. maimaiga conidia to attach and germinate on a substrate, a goniometer was used to determine relative hydrophobicity of larval cuticles. L. dispar cuticle was more hydrophobic than cuculliine cuticle, suggesting that a high level of hydrophobicity could be a required characteristic for hosts. Cuticles from four cuculliine species and L. dispar were sequentially extracted using hexane, chloroform, and methanol. Conidia were showered onto glass slides coated with the different extracts and germination was quantified. Methanol extracts of cuculliine cuticle consistently decreased germination, compared to all extracts of L. dispar cuticle. For all L. dispar extracts, the majority of conidia produced germ tubes, which is a normal prerequisite for cuticular penetration. For the cuculliines, conidia exposed to hexane and chloroform extracts produced secondary conidia as did all controls, but the conidia exposed to cuculliine methanol extracts that germinated produced germ tubes. These studies demonstrated that a range of factors act in concert to prevent E. maimaiga infection of the cuculliine species investigated.     

Fine Structure of Body Wall Cuticle of Females of Eight Genera of Heteroderidae

Body wall cuticle of adult females of eight genera within the Heteroderidae was examined by transmission electron microscopy for comparison with previously studied species within the family. Cuticle structure was used to test some current hypotheses of phylogeny of Heteroderidae and to evaluate intrageneric variability in cuticle layering. Verutus, Rhizonema, and Meloidodera possess striated cuticle surfaces and have the simplest layering, suggesting that striations have not necessarily arisen repeatedly in Heteroderidae through convergent or parallel evolution. Atalodera and Thecavermiculatus possess similar cuticles with derived characteristics, strengthening the hypothesis that the two genera are sister groups. Similarly, the cuticle of Cactodera resembles the specialized cuticle of Globodera and Punctodera in having a basal layer (D) and a surface layer infused with electron-dense substance. Heterodera betulae has a unique cuticle in which the thickest layer (C) is infiltrated with an electron-dense matrix. Little intrageneric difference was found between cuticles of two species of Meloidodera or between two species of Atalodera. However, Atalodera ucri has a basal layer (E) not found in other Heteroderidae. The most striking intrageneric variation in cuticle structure was observed between the thin three-layered cuticle of Sarisodera africana and the much thicker four-layered cuticle of Sarisodera hydrophila; results do not support monophyly of Sarisodera.