Nanopore Formation in the Cuticle of an Insect Olfactory Sensillum

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Gradients and the Specification of Planar Polarity in the Insect Cuticle

In addition to specifying cell fate, there is a wealth of evidence that molecular gradients are also primarily responsible for specifying cell polarity, particularly in the plane of epithelial sheets (“planar polarity”). The first compelling evidence of a role for gradients in specifying planar polarity came from transplantation experiments in the insect cuticle. More recent molecular genetic analyses in the fruit fly Drosophila have begun to give insights into the molecular nature of the gradients involved, and how they are interpreted at the cellular level.Development requires the coordinated specification of at least three attributes: cell fate, tissue size, and cell polarity. In both theory and practice, all three can be specified by the action of gradients. This article examines the experimental evidence for gradients acting to specify cell polarity in developing tissues, considers the mechanisms by which they are thought to act, and discusses what remains unknown. The problem of how cell polarity is specified in the plane of a tissue (“planar polarity”) is addressed. The tissues discussed are all formed from epithelial sheets that also show apicobasal cell polarity.For more than half a century, the preeminent system for studying the regulation of planar polarity in epithelia has been the insect cuticle. This lends itself to the study of the problem by virtue of often being adorned by structures such as hairs, scales, ridges, or other protrusions that reveal the polarity of the underlying cells. However, the lack of polarized structures on the surface of other epithelial-derived tissues should not be taken as evidence that the cells are not planar polarized, because often such polarity is cryptically expressed and only becomes apparent when the cells participate in a polarized process, such as cell division or cell intercalation.     

Nonspecific Factors Involved in Attachment of Entomopathogenic Deuteromycetes to Host Insect Cuticle

The attachment of the conidia of the insect-pathogenic fungi Nomuraea rileyi, Beauveria bassiana, and Metarrhizium anisopliae to insect cuticle was mediated by strong binding forces. The attachment was passive and nonspecific in that the conidia adhered readily to both host and nonhost cuticle preparations. The hydrophobicity of the conidial wall and the insect epicuticle appeared to mediate the adhesion process. Detergents, solvents, and high-molecular-weight proteins known to neutralize hydrophobicity reduced conidial binding when added to conidium-cuticle preparations. However, these chemicals did not remove the hydrophobic components from the epicuticle or from conidial preparations. The outer surface of the conidium consists of a resilient layer of well-organized fascicles of rodlets. Intact rodlets extracted from B. bassiana conidia bound to insect cuticle and exhibited the hydrophobicity expressed by intact conidia. Both electrostatic charges and various hemagglutinin activities were also present on the conidial surface. However, competitive-inhibition studies indicated that these forces played little, if any, role in the adhesion process.     

Sites of Synthesis and Transport Pathways of Insect Hydrocarbons: Cuticle and Ovary as Target Tissues

SYNOPSIS. The outer surface of insects is covered with a lipidlayer that provides water-proofing and protection against environmentalstresses. Hydrocarbons (HC) are major constituents of this epicuticularwax and they also serve as semiochemicals. In some insects HCare also exploited as biosynthetic precursors for pheromones.HC are synthesized by oenocyteswhich are situated in the integumentor hemocoel. Shuttling of HC to the epicuticie, fat body, andgonads requires transport through an aqueous medium. Insects,unlike vertebrates, use a versatile lipoprotein to effect lipidtransport and to selectively deliver lipids to specific tissues.A high-density hemolymph lipoprotein (lipophorin [Lp]) servesthis function.In adult females of the German cockroach (Blattellagermanica), Lp carries both HC and a contact sex pheromone.Lipophorin is a multi-functional lipid carrier serving alsoas a juvenile hormone binding protein in many insects. Studiesofthe interactions between Lp and HC are beginning to unravelthe routes used in delivering HC to target tissues. We discussthepathways and dynamics of loading of Lp with HC and HC-derivedpheromones, their transport through the hemolymph, and depositionin various tissues, including the epicuticie, ovaries, and pheromone-emittingglands.     

竹柏属叶角质层微形态的观察

利用扫描电镜对竹柏属（Nageia）6种植物叶角质层内外表面进行了细致的观察。发现竹柏属植物叶角质层特征具有明显的种间差异,利用这些差异能够将形态上较难区分的类群区分开。同时,根据叶角质层内表面特征,支持将台湾竹柏（Nageia nankoensis）和窄叶竹柏（Nageia formosensis）从广义竹柏中分离成两个不同种的观点。     

Functional Constraints on Insect Immune System Components Govern Their Evolutionary Trajectories

Roles of constraints in shaping evolutionary outcomes are often considered in the contexts of developmental biology and population genetics, in terms of capacities to generate new variants and how selection limits or promotes consequent phenotypic changes. Comparative genomics also recognizes the role of constraints, in terms of shaping evolution of gene and genome architectures, sequence evolutionary rates, and gene gains or losses, as well as on molecular phenotypes. Characterizing patterns of genomic change where putative functions and interactions of system components are relatively well described offers opportunities to explore whether genes with similar roles exhibit similar evolutionary trajectories. Using insect immunity as our test case system, we hypothesize that characterizing gene evolutionary histories can define distinct dynamics associated with different functional roles. We develop metrics that quantify gene evolutionary histories, employ these to characterize evolutionary features of immune gene repertoires, and explore relationships between gene family evolutionary profiles and their roles in immunity to understand how different constraints may relate to distinct dynamics. We identified three main axes of evolutionary trajectories characterized by gene duplication and synteny, maintenance/stability and sequence conservation, and loss and sequence divergence, highlighting similar and contrasting patterns across these axes amongst subsets of immune genes. Our results suggest that where and how genes participate in immune responses limit the range of possible evolutionary scenarios they exhibit. The test case study system of insect immunity highlights the potential of applying comparative genomics approaches to characterize how functional constraints on different components of biological systems govern their evolutionary trajectories.     

Comparative Proteomics Studies of Insect Cuticle by Tandem Mass Spectrometry: Application of a Novel Proteomics Approach to the Pea Aphid Cuticular Proteins

The cuticle is a biological composite material consisting principally of N‐acetylglucosamine polymer embedded in cuticular proteins (CPs). CPs have been studied and characterized by mass spectrometry in several cuticular structures and in many arthropods. Such analyses were carried out by protein extraction using SDS followed by electrophoresis, allowing detection and identification of numerous CPs. To build a repertoire of cuticular structures from Bombyx mori, Apis mellifera and Anopheles gambiae the use of SDS and electrophoresis was avoided. Using the combination of hexafluoroisopropanol and of a surfactant compatible with MS, a high number of CPs was identified in An. gambiae wings, legs and antennae, and in the thoracic integument cuticle of Ap. mellifera pupae. The exoskeleton analysis of B. mori larvae allowed to identify 85 CPs from a single larva. Finally, the novel proteomics approach was tested on cuticles left behind after the molt from the fourth instar of Acyrthosiphon pisum. Analysis of these cast cuticles allowed to identify 100 Ac. pisum CPs as authentic cuticle constituents. These correspond to 68% of the total putative CPs previously annotated for this pea aphid. While this paper analyzes only the recovered cuticular proteins, peptides from many other proteins were also detected.     

Cuticle protein in Locusta migratoria

• 1.1. The total protein content and the soluble proteins of the cuticle of male fifth instar and newly moulted adult locusts were analysed.
• 2.2. Protein was deposited in cuticle in a stepwise manner whereas chitin deposition was continuous.
• 3.3. Resorption of cuticular protein preceded resorption of chitin following apolysis.
• 4.4. Immunological and electrophoretic analyses indicated that certain cuticular proteins were also present in the haemolymph.
• 5.5. Certain water soluble proteins appeared to be characteristic of the newly deposited cuticle and were presumably bound to the cuticular matrix as development continued.
• 6.6. Despite an increase in total soluble protein following apolysis, no evidence of new proteins was detected. It was deduced that the initial step in protein resorption from the old cuticle is the release of the protein from its cuticular bonds.

     

观音座莲目的角质层特征

运用扫描电镜和光学显微镜对观音座莲目4种(属)植物的叶角质层进行了研究。结果表明,其间存在明显共性:表皮构造均为单面气孔式,上下表皮细胞垂周壁皆呈不同程度的波状起伏,气孔器类型皆为环列型。需要指出的是观音座莲目的全部6属植物均具环列型的气孔器,这表明该特征在目一级水平上具有重要的分类学及系统学意义。同时天星蕨属的角质层特征进一步支持了将天星蕨属上升为天星蕨科的观点。     

Cuticle differentiation during Drosophila embryogenesis

The constitutive criterion for the evolutionary successful clade of ecdysozoans is a protective exoskeleton. In insects the exoskeleton, the so-called cuticle consists of three functional layers, the waterproof envelope, the proteinaceous epicuticle and the chitinous procuticle that are produced as an extracellular matrix by the underlying epidermal cells. Here, we present our electron-microscopic study of cuticle differentiation during embryogenesis in the fruit fly Drosophila melanogaster. We conclude that cuticle differentiation in the Drosophila embryo occurs in three phases. In the first phase, the layers are established. Interestingly, we find that establishment of the layers occurs partially simultaneously rather than in a strict sequential manner as previously proposed. In the second phase the cuticle thickens. Finally, in the third phase, when secretion of cuticle material has ceased, the chitin laminae acquire their typical orientation, and the epicuticle of the denticles and the head skeleton darken. Our work will help to understand the phenotypes of embryos mutant for genes encoding essential cuticle factors, in turn revealing mechanisms of cuticle differentiation.     

Partitioning Yield Loss on Yellow Squash into Nematode and Insect Components

The effect of a contplex of several insect and nematode pests on yield of yellow squash (Cucurbita pepo L.) was examined in two field tests in southern Florida. Applications of permethrin for insect control and oxamyl primarily for nematode control plus some insect control were made alone and in combination to achieve differential reduction of various insect and nematode components contributing to yield loss. The effect of these components on yield was further analyzed by multiple regression. Yield losses in weight of small fruit to nematode and insect pests together were estimated at 23.4% and 30.4% in each of the two tests, respectively. In the first test, this loss was attributed to the melonworm, Diaphania hyalinata, while in the second test, it was attributed to D. hyalinata and the nematodes Quinisulcius acutus and particularly Rotylenchulus reniforrnis. D. hyalinata accounted for further losses of 9.0% and 10.3%, respectively, from direct damage to the fruit. Despite the presence of low levels of Diabrotica balteata, Liriomyza sativae, and Myzus persicae, yields were little affected by these pests. Prediction of yield loss by multiple regression analysis was more accurate when both insect and nematode populations were present in the plots than when nematodes alone were present.