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PubMedDate not supplied

Digestion of nectar and insects by Palestine sunbirds.

In nectarivorous birds, specialization for feeding on nectar has led to a simple gut structure with high sugar digestive efficiencies and rapid gut passage rates. These features of the digestive system may make digestion of more complex, protein-rich food sources, such as pollen or insects, less efficient. In this light, we hypothesized that sugar metabolizability in nectarivorous Palestine sunbirds (Nectarinia osea) would be high, whereas nitrogen metabolizability would be lower than typically found for birds. We measured glucose and fructose apparent metabolizabilities (*MCs) and transit times (TTs) in eight Palestine sunbirds offered either a 10% or a 50% mixed sugar diet. *MC for glucose (99.9%+/-0.1%) was significantly greater than for fructose (99.6%+/-0.4%; ANOVA; P<0.001). TT for the 10% sugar diet (26.3+/-10.1 min) was significantly shorter than for the 50% sugar diet (47.0+/-7.8 min). We measured nitrogen true metabolizability (MC) and TT in Palestine sunbirds offered a daily fruit fly intake of either 40 or 200 flies. Nitrogen MC was not significantly different between diets, and average MC for both diets was 58.5%+/-8.5% (n=8). TT was not significantly different when birds ate 10 flies (50.1+/-13.6 min) than when they ate 50 flies (48.5+/-16.5 min). The high sugar *MC and relatively rapid TT of nectar in Palestine sunbirds are similar to those found for other nectarivorous species. Transit times of insect material are longer that those found in small insectivorous species. However, MCs of insect material are lower. Thus, even though sunbirds consume easily digestible soft-bodied insects, they are less efficient at extracting protein than nonnectarivores.

Animals↗
PubMed2004

Should models of disease dynamics in herbivorous insects include the effects of variability in host-plant foliage quality?

Interactions between insects and their baculovirus pathogens are often described using simple disease models. Baculoviruses, however, are transmitted when insects consume virus-contaminated foliage, and foliage variability, whether within or between host-plant species, can affect viral infectiousness. Insect-baculovirus interactions may thus be embedded in a tritrophic interaction with the insect's host plant, but disease models include only the host and the pathogen. We tested these models by measuring the transmission of a baculovirus of gypsy moths (Lymantria dispar) on red oak (Quercus rubra) and white oak (Quercus alba) in the field in six experiments over four years. In all experiments, there were only weak effects of host-tree species, and in only one did the best-fitting model include tree species effects. These weak effects of foliage variability on transmission were not due to a lack of foliage variability on viral infectiousness, because when larvae were force-fed virus-contaminated foliage, infection rates were higher on white oak. Our results suggest that feeding behavior plays an important role in baculovirus transmission and that models can usefully describe baculovirus dynamics even without including foliage variability. Our work provides a clear example of how two-species models are sometimes sufficient to describe what appear to be tritrophic interactions.

Animals↗
PubMed2006

Thermodynamics constrains the evolution of insect population growth rates: "warmer is better".

Diverse biochemical and physiological adaptations enable different species of ectotherms to survive and reproduce in very different temperature regimes, but whether these adaptations fully compensate for the thermodynamically depressing effects of low temperature on rates of biological processes is debated. If such adaptations are fully compensatory, then temperature-dependent processes (e.g., digestion rate, population growth rate) of cold-adapted species will match those of warm-adapted species when each is measured at its own optimal temperature. Here we show that cold-adapted insect species have much lower maximum rates of population growth than do warm-adapted species, even when we control for phylogenetic relatedness. This pattern also holds when we use a structural-equation model to analyze alternative hypotheses that might otherwise explain this correlation. Thus, although physiological adaptations enable some insects to survive and reproduce at low temperatures, these adaptations do not overcome the "tyranny" of thermodynamics, at least for rates of population increase. Indeed, the sensitivity of population growth rates of insects to temperature is even greater than predicted by a recent thermodynamic model. Our findings suggest that adaptation to temperature inevitably alters the population dynamics of insects. This result has broad evolutionary and ecological consequences.

Adaptation, Physiological↗
PubMedDate not supplied

Post-translational processing of barley beta-glucan endohydrolases in the baculovirus-insect cell expression system.

Two cDNAs encoding barley (1-->3,1-->4)-beta-glucanase (EC 3.2.1.73) isoenzymes EI and EII have been expressed in Spodoptera frugiperda (Sf9) cell cultures using the baculovirus AcNPV vector. Modifications to both the 5' and 3' ends of the cDNAs were required before satisfactory levels of expression were obtained. The modified cDNAs directed high levels of (1-->3,1-->4)-beta-glucanase expression in the Sf9 insect cell cultures, with yields of approximately 10 mg/liter of isoenzyme EI (expEI) and 15 mg/liter of isoenzyme EII (expEII). Amino acid sequence analyses showed that the expressed enzymes were processed correctly at their amino termini. However, affinity chromatography of the isoenzyme expEII on concanavalin-A (conA)-Sepharose indicated that, although the enzyme is glycosylated, the structures of the carbohydrate chains differ from those of the native enzyme. When a cDNA encoding the homologous barley (1-->3)-beta-glucanase (EC 3.2.1.39) isoenzyme GII was expressed in insect cells, aberrant amino-terminal processing of the nascent polypeptide was sometimes observed. The forms with incompletely removed signal peptides retained their substrate specificity, but exhibited slightly reduced catalytic efficiency, altered chromatographic behavior, and reduced stability at elevated temperatures. The results show that high levels of expression of recombinant plant proteins can be obtained in insect cells, but they emphasize the need to characterize thoroughly the products that are expressed in the heterologous insect cell system before comparisons are made with the native enzyme or with engineered enzyme mutants.

Amino Acid Sequence↗
PubMed2007

Solar ultraviolet-B radiation and insect herbivory trigger partially overlapping phenolic responses in Nicotiana attenuata and Nicotiana longiflora.

BACKGROUND AND AIMS: Plants exposed to solar ultraviolet-B radiation (UV-B, 280-315 nm) frequently suffer less insect herbivory than do plants that receive attenuated levels of UV-B. This anti-herbivore effect of solar UV-B exposure, which has been documented in several ecosystems, is in part mediated by changes in plant tissue quality. Exposure to UV-B can modify the abundance of a number of secondary metabolites, including phenolic compounds with potential impacts on insect herbivores. The aim of this study is to assess the potential anti-herbivore role of UV-B-induced phenolic compounds by comparing the phenolic profiles induced by UV-B and simulated insect herbivory in two wild species of the genus Nicotiana. METHODS: Plants grown under field and glasshouse conditions were exposed to contrasting levels of UV-B. Half of the plants of the attenuated UV-B treatment were given a simulated herbivory treatment, where leaves were mechanically damaged and immediately treated with oral secretions of Manduca sexta caterpillars. This treatment is known to mimic the impact of real herbivory on the expression of plant defences in Nicotiana. Phenolic profiles induced by UV-B and simulated herbivory were characterized using high-performance liquid chromatography-mass spectrometry (HPLC-MS). KEY RESULTS: UV-B induced the accumulation of several UV-absorbing phenolic compounds that are known to play a significant role in UV-B screening. Interestingly, there was a significant convergence in the phenolic profiles induced by UV-B and simulated herbivory: chlorogenic acid and dicaffeoylspermidine isomers, in particular, displayed a similar pattern of response to these stimuli. In contrast, rutin, the only flavonoid that accumulated in significant quantities in the experiments, was only induced by UV-B. CONCLUSIONS: The results suggest that the anti-herbivory effect induced by UV-B may be mediated at least in part by the accumulation of phenylpropanoid derivatives that are similar to those induced by the plant in response to insect herbivory.

Animals↗
PubMed2001

Engineering lepidopteran insect cells for sialoglycoprotein production by genetic transformation with mammalian beta 1,4-galactosyltransferase and alpha 2,6-sialyltransferase genes.

Recombinant mammalian glycoproteins produced by the baculovirus-insect cell expression system usually do not have structurally authentic glycans. One reason for this limitation is the virtual absence in insect cells of certain glycosyltransferases, which are required for the biosynthesis of complex, terminally sialylated glycoproteins by mammalian cells. In this study, we genetically transformed insect cells with mammalian beta 1,4-galactosyltransferase and alpha 2,6-sialyltransferase genes. This produced a new insect cell line that can express both genes, serve as hosts for baculovirus infection, and produce foreign glycoproteins with terminally sialylated N-glycans.

Animals↗
PubMed2003

Evidence for a sialic acid salvaging pathway in lepidopteran insect cells.

We previously described a transgenic insect cell line, Sfbeta4GalT/ST6, that expresses mammalian beta-1,4-galactosyltransferase and alpha2,6-sialyltransferase genes and produces glycoproteins with terminally sialylated N-glycans. The ability of these cells to produce sialylated N-glycans was surprising because insect cells contain only small amounts of sialic acid and no detectable CMP-sialic acid. Thus, it was of interest to investigate potential sources of sialic acids for sialoglycoprotein synthesis by these cells. We found that Sfbeta4GalT/ST6 cells can produce sialylated N-glycans when cultured in the presence but not in the absence of fetal bovine serum. The serum component(s) supporting N-glycan sialylation by Sfbeta4GalT/ST6 cells is relatively large-it was not removed by dialysis in a 50,000-molecular-weight cutoff membrane. Serum-free media supplemented with purified fetuin but not asialofetuin supported N-glycan sialylation by Sfbeta4GalT/ST6 cells. The terminally sialylated N-glycans isolated from fetuin also supported glycoprotein sialylation by Sfbeta4GalT/ST6 cells. Finally, serum-free medium supplemented with N-acetylneuraminic acid or N-acetylmannosamine supported glycoprotein sialylation by Sfbeta4GalT/ST6 cells but to a much lower degree than serum or fetuin. These results provide the first evidence of a sialic acid salvaging pathway in insect cells, which begins to explain how Sfbeta4GalT/ST6 and other transgenic insect cell lines can sialylate recombinant glycoproteins in the absence of a more obvious source of CMP-sialic acid.

Animals↗
PubMed2003

Mechanisms and diversity of resistance to insect pests in wild relatives of groundnut.

The levels of resistance to insect pests in cultivated groundnut (Arachis hypogaea) germplasm are quite low, and therefore, we screened 30 accessions of Arachis spp. and 12 derived lines for resistance to insect pests under field and greenhouse conditions. Accessions belonging to Arachis cardenasii, Arachis duranensis, Arachis kempff-mercadoi, Arachis monticola, Arachis stenosperma, Arachis paraguariensis, Arachis pusilla, and Arachis triseminata showed multiple resistance to the leaf miner Aproaerema modicella, Helicoverpa armigera, Empoasca kerri, and to rust, Puccnia arachidis Speg., and late leaf spot, Cercosporidium personatum (Berk. et Curt.). Arachis cardenasii (ICG 8216), Arachis ipaensis (ICG 8206), A. paraguariensis (ICG 8130), and Arachis appressipila (ICG 8946) showed resistance to leaf feeding and antibiosis to Spodoptera litura under no-choice conditions. Six lines, derived from wild relatives, showed resistance to H. armigera and S. litura, and/or leaf miner. Plant morphological characteristics such as main stem thickness, hypanthium length, leaflet shape and length, leaf hairiness, standard petal length and petal markings, basal leaflet width, main stem thickness and hairiness, stipule adnation length and width, and peg length showed significant correlation and/or regression coefficients with damage by H. armigera, S. litura, and leafhoppers, and these traits can possibly be used as markers to select for resistance to these insect pests. Principal component analysis placed the Arachis spp. accessions into five groups, and these differences can be exploited to diversify resistance to the target insect pests in groundnut.

Animals↗
PubMedDate not supplied

Hypothesis testing in evolutionary developmental biology: a case study from insect wings.

Developmental data have the potential to give novel insights into morphological evolution. Because developmental data are time-consuming to obtain, support for hypotheses often rests on data from only a few distantly related species. Similarities between these distantly related species are parsimoniously inferred to represent ancestral aspects of development. However, with limited taxon sampling, ancestral similarities in developmental patterning can be difficult to distinguish from similarities that result from convergent co-option of developmental networks, which appears to be common in developmental evolution. Using a case study from insect wings, we discuss how these competing explanations for similarity can be evaluated. Two kinds of developmental data have recently been used to support the hypothesis that insect wings evolved by modification of limb branches that were present in ancestral arthropods. This support rests on the assumption that aspects of wing development in Drosophila, including similarities to crustacean epipod patterning, are ancestral for winged insects. Testing this assumption requires comparisons of wing development in Drosophila and other winged insects. Here we review data that bear on this assumption, including new data on the functions of wingless and decapentaplegic during appendage allocation in the red flour beetle Tribolium castaneum.

Animals↗
PubMed2003

IPM-compatibility of foliar insecticides for citrus: indices derived from toxicity to beneficial insects from four orders.

A series of compounds representing four major pesticide groups were tested for toxicity to beneficial insects representing four different insect orders: Coleoptera (Coccinellidae), Hemiptera (Anthocoridae), Hymenoptera (Aphelinidae), and Neuroptera (Chrysopidae). These materials included organophosphates (methidathion, esfenvalerate and phosmet), carbamates (carbofuran, methomyl and carbaryl), pyrethroids (bifenthrin, fenpropathrin, zeta-cypermethrin, cyfluthrin and permethrin) and the oxadiazine indoxacarb. Toxicity to coccinellid and lacewing species was assessed by treating 1st instar larvae with the recommended field rate of commercial products, and two 10 fold dilutions of these materials, in topical spray applications. Adult Aphytis melinus Debach and 2nd instar Orius insidiosus (Say) were exposed to leaf residues of the same concentrations for 24 h. ANOVA performed on composite survival indices derived from these data resolved significant differences among materials with respect to their overall toxicity to beneficial insects. Cyfluthrin, fenpropathrin and zeta-cypermethrin all increased the developmental time of the lacewing and one or more coccinellid species for larvae that survived topical applications. Bifenthrin increased developmental time for two coccinellid species and decreased it in a third. Indoxacarb (Avaunt WG, DuPont Corp.) ranked highest overall for safety to beneficial insects, largely because of its low dermal toxicity to all species tested. Zeta-cypermethrin (Super Fury), FMC Corporation) received the second best safety rating, largely because of its low toxicity as a leaf residue to A. melinus and O. insidiosus. Phosmet (Imidan 70W, Gowan Co.) and methidathion (Supracide 25W, Gowan Co.) ranked high for safety to coccinellid species, but compounds currently recommended for use in citrus such as fenpropathrin (Danitol 2.4EC, Sumimoto Chem. Co.) and carbaryl (Sevin XLR EC, Rhone Poulenc Ag. Co.) ranked very low for IPM-compatibility based on their relatively high toxicity to all species tested.

Animals↗
PubMed2004

DrawWing, a program for numerical description of insect wings.

There is usually a pattern of veins on an insect wing. This pattern is species-specific and is used taxonomically. For example, the coordinates of some characteristic points on the wing are used to compare vein patterns. The characteristic points are often vein junctions or vein ends. A tool is presented that enables automatic identification of vein junctions. An image of an insect wing is used to determine the wing outline and veins. The vein skeleton is obtained using a thinning algorithm. Bezier splines are fitted to both the wing outline and the vein skeleton. The splines are saved in an encapsulated postscript file. Another output file in text format contains the coordinates of vein junctions. Both the program and its source code are available under GNU General Public License at [www.cyf-kr.edu.pl/~rotofils/drawwing.html]. The program presented in this paper automatically provides a numerical description of an insect wing. It converts an image of an insect wing to a list of coordinates of vein junctions, and a wing diagram that can be used as an illustration. Coordinates of the vein junctions extracted by the program from wing images were used successfully to discriminate between males of Dolichovespula sylvestris and Dolichovespula saxonica.

Animals↗
PubMed2004

Bt transgenic crops do not have favorable effects on resistant insects.

Sayyed et al. (Ecology Letters (2003) 6: 167-169) hypothesized that insecticidal Bacillus thuringiensis (Bt) toxins produced by transgenic crops could have nutritionally favorable effects that increase the fitness of resistant insects eating such crops. This idea was based on increased pupal weight of resistant larvae of diamondback moth, Plutella xylostella (L.), fed leaf discs treated externally with a Bt toxin. We summarize evidence from diamondback moth and other pests showing that the Bt toxins in transgenic crops do not enhance performance of resistant insects. Aside from a few notable exceptions in which performance of resistant insects did not differ between Bt and non-Bt crops, Bt crops had adverse affects on resistant insects.

Animals↗
PubMed1991

Carrion insects of the Egyptian western desert.

A general survey was made on the zoosaprophagous insects and their associates in a natural ecosystem in the Egyptian western desert (80 km west of Alexandria, 12 km from the Mediterranean Sea shore). Two types of traps were used, one for flying insects and the other for soil-burrowing insects. Two types of decaying media were used as baits: the common freshwater fish (Tilapia zilii Gerv.) and the desert snail (Eremina desertorum). More than 30 insect species were trapped. The following orders and families were represented: Diptera (Calliphoridae, Sarcophagidae, Muscidae); Coleoptera (Histeridae, Scarabaeidae, Dermestidae, Tenebrionidae); Hymenoptera (Chalcididae, Pteromalidae, Eulophidae, Formicidae). Monthly totals of numbers trapped in each of these groups are presented.

Animals↗
PubMed2005

Effects of antemortem ingestion of ethanol on insect successional patterns and development of Phormia regina (Diptera: Calliphoridae).

The effects of antemortem ingestion of ethanol by domestic pigs, Sus scrofa L., on postmortem insect successional patterns and the development of Phormia regina (Meigen) were studied during summer 2003 in Blacksburg, VA. Insect samples were collected from the carcasses of ethanol-treated and untreated pigs for 10 d postmortem during two successional studies. In total, 32 insect taxa were collected during the two studies, with 29 and 27 taxa observed on the carcasses of ethanol-treated and untreated pigs, respectively. The earliest arrivers to both carcass types were dipterans. This group was represented by six families, with P. regina and Phaenicia coeruleiviridis (Macquart) being the most common calliphorids. Beetles in six families were collected on the carcasses of ethanol-treated pigs, but only three of the families were collected on carcasses of the untreated pigs. Permutation analyses to test the null hypothesis of no similarity between successional patterns of insect taxa from carcasses of ethanol-treated and untreated pigs showed that the successional patterns were similar between carcass types in the first (P = 0.003) and the second (P = 0.01) studies. The results of the development study of P. regina maggots in the field show that there was a significant difference between the distributions of length for maggots reared on loin tissue from ethanol-treated and untreated pigs. Maggots that fed on tissue from ethanol-treated pigs took approximately 11.9 h longer to reach the pupal stage than maggots that fed on tissue from untreated pigs. The longer developmental time for maggots on tissue from ethanol-treated pigs was due mainly to the longer postfeeding period of the third instar.

Animals↗
PubMed2006

Phloem sap proteins: their identities and potential roles in the interaction between plants and phloem-feeding insects.

The phloem is a well-known target of sucking and piercing insects that utilize the transported fluid as their major nutrient source. In addition to small molecules like sugars and amino acids, phloem sap of higher land plants contains proteins that can accumulate up to high concentrations. Although the knowledge about the identities of these phloem sap proteins is increasing, the functions of most of them are still poorly understood. Since many phloem sap proteins have predicted roles in wound and defence responses, they constitute a class of compounds that can potentially influence plant-insect interactions. However, there are as yet no studies published that have examined direct effects of phloem sap proteins on insect feeding or vice versa. This review summarizes the current knowledge about the identities of phloem sap proteins, focused on polypeptides with probable functions in wound and defence reactions, and their potential impact on plant-insect interactions is discussed.

Animals↗
PubMed2004

Structural requirements of signal peptide in insect cell.

In order to increase the proteinic secretion quantity of production in insect cell, the N-terminal and the hydrophobic core region of the chicken lysozyme signal peptide (CLSP) was altered. A hybrid gene composed of CLSP gene and human lysozyme (HLY) gene from short DNA oligomers was used for the production of recombinant HLY in insect cell using vacuole virus expression system. In contrast with the results in yeast, the introduction of basic residues in the N-terminal region did not make the amount of secretion increase in insect cell. On the other hand, when the sequence of CLSP was changed into Leu-rich type, the amount of HLY secretion increased sharply. Although they are eukaryotes, the structural requirements of signal peptides may have some differences in yeast and insect cell.

Amino Acid Sequence↗
PubMed2005

Gene design of signal sequence for the effective secretion of recombinant protein using insect cell.

In order to increase the proteinic secretion quantity of production in insect cell, the chicken lysozyme signal peptide (CLSP) was altered, and the effect of mutations on secretion of human lysozyme (HLY), the bovine interferon beta-3, and the equine interferon alpha-1 were studied. A hybrid gene composed of CLSP gene and HLY gene was used for the production of recombinant HLY in insect cell (BmN4) using vacuole virus expression system. In contrast with the Leu rich signal peptide in previous reports, Val rich type, or Ile rich type decreased the secretion of HLY, and Phe rich type prevented it completely, in spite of the increase of hydrophobicity in the central core region of each signal peptide. Besides the hydrophobicity, the tertiary structure in this region also might influence the secretion of HLY in insect cells. Then, Leu-rich signal peptide was used for the secretion of the bovine interferon beta-3, or the equine interferon alpha-1, resulted in the remarkable increase of the amount of the secretion in insect cells.

Amino Acid Sequence↗
PubMed2005

Signal signature and transcriptome changes of Arabidopsis during pathogen and insect attack.

Plant defenses against pathogens and insects are regulated differentially by cross-communicating signaling pathways in which salicylic acid (SA), jasmonic acid (JA), and ethylene (ET) play key roles. To understand how plants integrate pathogen- and insect-induced signals into specific defense responses, we monitored the dynamics of SA, JA, and ET signaling in Arabidopsis after attack by a set of microbial pathogens and herbivorous insects with different modes of attack. Arabidopsis plants were exposed to a pathogenic leaf bacterium (Pseudomonas syringae pv. tomato), a pathogenic leaf fungus (Alternaria brassicicola), tissue-chewing caterpillars (Pieris rapae), cell-content-feeding thrips (Frankliniella occidentalis), or phloem-feeding aphids (Myzus persicae). Monitoring the signal signature in each plant-attacker combination showed that the kinetics of SA, JA, and ET production varies greatly in both quantity and timing. Analysis of global gene expression profiles demonstrated that the signal signature characteristic of each Arabidopsis-attacker combination is orchestrated into a surprisingly complex set of transcriptional alterations in which, in all cases, stress-related genes are overrepresented. Comparison of the transcript profiles revealed that consistent changes induced by pathogens and insects with very different modes of attack can show considerable overlap. Of all consistent changes induced by A. brassicicola, Pieris rapae, and E occidentalis, more than 50% also were induced consistently by P. syringae. Notably, although these four attackers all stimulated JA biosynthesis, the majority of the changes in JA-responsive gene expression were attacker specific. All together, our study shows that SA, JA, and ET play a primary role in the orchestration of the plant's defense response, but other regulatory mechanisms, such as pathway cross-talk or additional attacker-induced signals, eventually shape the highly complex attacker-specific defense response.

Alternaria↗