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At least 469 records · Page 26Linked to original sources
PubMed2003

Insect resistance to Bacillus thuringiensis: alterations in the indianmeal moth larval gut proteome.

Insect resistance to the Cry toxins of Bacillus thuringiensis (Bt) has been examined previously using a number of traditional biochemical and molecular techniques. In this study, we utilized a proteomic approach involving two-dimensional differential gel electrophoresis, mass spectrometry, and function-based activity profiling to examine changes in the gut proteins from the larvae of an Indianmeal moth (IMM, Plodia interpunctella) colony exhibiting resistance to Bt. We found a number of changes in the levels of certain specific midgut proteins that indicate increased glutathione utilization, elevation in oxidative metabolism, and differential maintenance of energy balance within the midgut epithelial cells of the Bt-resistant IMM larva. Additionally, the electrophoretic migration pattern of a low molecular mass acidic protein, which apparently is an ortholog of F(1)F(0)-ATPase, was considerably altered in the Bt-resistant insect indicating that variations in amino acid content or modifications of certain proteins also are important components of the resistance phenomenon in the IMM. Furthermore, there was a dramatic decrease in the level of chymotrypsin-like proteinase in the midgut of the Bt-resistant larva, signifying that reduction of chymotrypsin activity, and subsequently decreased activation of Cry toxin in the insect midgut, is an important factor in the resistant state of the IMM. The proteomic analysis of larval gut proteins utilized in this study provides a useful approach for consolidating protein changes and physiological events associated with insect resistance to Bt. Our results support the hypothesis that physiological adaptation of insects and resistance to Bt is multifaceted, including protein modification and changes in the synthesis of specific larval gut proteins. We believe that increased oxidative metabolism may be an adaptive response of insects that undergo survival challenge and that it could mediate detoxification as well as higher rates of generalized and localized mutations that enhance their resistance and provide survival advantage.

Animals↗
PubMed2005

Radar studies of the vertical distribution of insects migrating over southern Britain: the influence of temperature inversions on nocturnal layer concentrations.

Insects migrating over two sites in southern UK (Malvern in Worcestershire, and Harpenden in Hertfordshire) have been monitored continuously with nutating vertical-looking radars (VLRs) equipped with powerful control and analysis software. These observations make possible, for the first time, a systematic investigation of the vertical distribution of insect aerial density in the atmosphere, over temporal scales ranging from the short (instantaneous vertical profiles updated every 15 min) to the very long (profiles aggregated over whole seasons or even years). In the present paper, an outline is given of some general features of insect stratification as revealed by the radars, followed by a description of occasions during warm nights in the summer months when intense insect layers developed. Some of these nocturnal layers were due to the insects flying preferentially at the top of strong surface temperature inversions, and in other cases, layering was associated with higher-altitude temperature maxima, such as those due to subsidence inversions. The layers were formed from insects of a great variety of sizes, but peaks in the mass distributions pointed to a preponderance of medium-sized noctuid moths on certain occasions.

Altitude↗
PubMed1999

Odorant binding protein diversity and distribution among the insect orders, as indicated by LAP, an OBP-related protein of the true bug Lygus lineolaris (Hemiptera, Heteroptera).

Insect odorant binding proteins (OBPs) are thought to deliver odors to olfactory receptors, and thus may be the first biochemical step in odor reception capable of some level of odor discrimination. OBPs have been identified from numerous species of several insect orders, including Lepidoptera, Diptera, Coleoptera and Hymenoptera; all are holometabolous insects belonging to the monophyletic division of insects known as the Endopterygota. Recently, an antennal protein with OBP-like properties was identified from Lygus lineolaris, a hemipteran insect representing the Hemipteroid Assemblage, a sister division to the Endopterygota. The full length sequence of Lygus antennal protein (LAP) is presented in this report. In situ hybridization analysis revealed LAP expression in cell clusters associating with olfactory sensilla; expression was adult-specific, initiating in developing adult tissue during the transitional period that precedes the actual adult molt. Sequence analysis confirmed that LAP is homologous with the OBP-related protein family, and most similar to the OS-E and OS-F proteins of Drosophila, the ABPX proteins of Lepidoptera and the OBPRP proteins of the Coleoptera. Assuming that the OBP-related proteins represent one homologous family, the identification of LAP significantly expands the phylogenetic depth of that family and its underlying role in odor detection to encompass all members of the Endopterygota and Hemipteroid Assemblage, which comprise >90% of all insect species.

Amino Acid Sequence↗
PubMed1996

Glycosylation in lepidopteran insect cells: identification of a beta 1-->4-N-acetylgalactosaminyltransferase involved in the synthesis of complex-type oligosaccharide chains.

The choice for a heterologous expression system to produce glycoprotein therapeutics highly depends on its potential to perform mammalian-like posttranslational modifications such as glycosylation. To gain more insight into the glycosylation potential of the baculovirus mediated insect cell expression system, we have studied the expression of glycosyltransferases involved in complex-type N-glycosylation. Lepidopteran insect cell lines derived from Trichoplusia ni, Spodoptera frugiperda, and Mamestra brassicae were found to express a beta 1-->4- N-acetylgalactosaminyltransferase (beta 4-GalNAcT) that catalyzes the transfer of GalNAc from UDP-GalNAc to oligosaccharides and glycoproteins carrying a terminal beta-linked GlcNAc residue. These results suggest that Lepidopteran insect cells are capable of synthesizing complex-type carbohydrate chains containing GalNAc beta 1-->4GlcNAc (LacdiNAc) units. Baculovirus infection of the cells, however, resulted in a decrease in the activity of beta 4-GalNAcT from 80 to <1 pmol.min-1 mg-1 protein within 48 h post infection. Furthermore, considerable beta-N-acetylgalactosaminidase and beta-N-acetylglucosaminidase activity was observed in insect cells, whether or not infected with baculovirus, as well as in the culture medium. These enzyme activities could be responsible for degradation of complex-type oligosaccharide chains containing LacdiNAc units. Our findings provide an enzymatic basis for the observation that most recombinant glycoproteins produced by baculovirus infected insect cells carry oligomannosidic-type N-linked glycans, in spite of the fact that uninfected insect cells have the potential for the synthesis of mammalian-like complex-type glycans.

Animals↗
PubMed2003

Do rice hybrids have heterosis for insect resistance? A study with Nilaparvata lugens (Hemiptera: Delphacidae) and Marasmia patnalis (Lepidoptera: Pyralidae).

Antibiosis-based resistance to two insect pests of rice, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) and Marasmia patnalis Bradley (Lepidoptera: Pyralidae), was compared in 11 F1 hybrids and their parental lines. Our objective was to determine whether hybrids show heterosis (hybrid vigor) for insect resistance or susceptibility. Heterosis is defined as the amount by which a hybrid exceeds its midparent value or its better parent. Overall, we did not find evidence of heterosis or heterobeltiosis (a type of heterosis in which a hybrid exceeds its better parent) for antibiosis-based resistance or susceptibility to either of the insects. One hybrid, IR64616H, seemed more resistant to M. patnalis than its better parent but none of the other hybrids showed heterobeltiosis for resistance or susceptibility to either insect. Three hybrids had resistance to N. lugens that exceeded their midparent value, possibly due to dominant resistance in one of the parents. The increased frequency and severity of insect outbreaks on hybrid rice that have been reported in China may be attributable to factors other than diminished antibiosis in hybrids, such as greater attractiveness of hybrids to migrating or dispersing insects or differences in agronomic practices applied to hybrids and inbred rice cultivars.

Animals↗
PubMed2000

Comparative analysis of secondary structure of insect mitochondrial small subunit ribosomal RNA using maximum weighted matching.

Comparative analysis is the preferred method of inferring RNA secondary structure, but its use requires considerable expertise and manual effort. As the importance of secondary structure for accurate sequence alignment and phylogenetic analysis becomes increasingly realised, the need for secondary structure models for diverse taxonomic groups becomes more pressing. The number of available structures bears little relation to the relative diversity or importance of the different taxonomic groups. Insects, for example, comprise the largest group of animals and yet are very poorly represented in secondary structure databases. This paper explores the utility of maximum weighted matching (MWM) to help automate the process of comparative analysis by inferring secondary structure for insect mitochondrial small subunit (12S) rRNA sequences. By combining information on correlated changes in substitutions and helix dot plots, MWM can rapidly generate plausible models of secondary structure. These models can be further refined using standard comparative techniques. This paper presents a secondary structure model for insect 12S rRNA based on an alignment of 225 insect sequences and an alignment for 16 exemplar insect sequences. This alignment is used as a template for a web server that automatically generates secondary structures for insect sequences.

Algorithms↗
PubMed1999

Enhancement of secretion of human procollagen I in mouse HSP47-expressing insect cells.

We previously demonstrated that insect cells were able to synthesize recombinant human procollagen I as triple-helical heterotrimers when transfected with cDNAs of both proalpha1(I) and proalpha2(I) chains. However, most of the heterotrimers were retained within the cells, unlike in the case of mammalian cells [Tomita, M., Kitajima, T., and Yoshizato, K. (1997) J. Biochem. 1061-1069]. In an attempt to improve the secretion of the heterotrimers, we introduced the putative collagen-specific chaperone HSP47 into this insect expression model. Mouse HSP47 produced by the insect cells bound intracellularly to both human proalpha1(I) and proalpha2(I) chains and enhanced the secretion of procollagen I heterotrimers. HSP47 was also coexpressed with either proalpha1(I) chains or proalpha2(I) chains, which showed that it enhanced the secretion of the former but not the latter. This selective effect of HSP47 was similarly observed in the cells treated with inhibitors of procollagen triple helix formation, indicating that HSP47 can also accelerate the secretion of non-helical procollagens. HSP47 did not change the intracellular solubility of proalpha1(I) and proalpha2(I) chains in 1% NP-40, eliminating the possibility that it prevents proalpha chains from aggregating into insoluble forms within the insect cells. We concluded that HSP47 can play a role in the secretion of alpha1(I)-procollagen chains in the insect cell model. The present study also demonstrated the dissimilarity in the mechanism of folding and secretion of the expressed procollagen I between the insect and mammalian cells.

Animals↗
PubMed1991

Human heterophile antibodies recognizing epitopes present on insect glycolipids.

As a consequence of detecting an IgM M-protein (naturally occurring diseased-state monoclonal antibody) immunoreactive to insect acidic glycolipids in a patient with demyelinating peripheral neuropathy, normal human sera were examined for the occurrence of heterophile antibodies directed against carbohydrate epitopes present on glycosphingolipids of Calliphora vicina (Insecta: Diptera). The insect glycolipids can be separated into neutral, zwitterionic, and acidic types, according to whether the oligosaccharide chains consist of neutral monosaccharides only, or carry an additional phospho-ethanolamine side chain and/or a beta-glucuronic acid residue, respectively. Natural antibody activity to these three classes of insect glycosphingolipids was detected in all normal human sera examined. The antibody activities were separated by sequential chromatography on affinity columns of octyl-Sepharose 4B-bound neutral and zwitterionic glycolipids into three populations with differing epitope-type specificities. As expected for heterophile antibodies, they are mainly of the IgM class. Population I recognized epitopes present on the three types of insect glycolipids, i.e., the neutral oligosaccharide chain backbone, the main determinant of which contains a terminal N-acetylhexosamine. Immunoreactivity is separable into at least four subpopulations of differing carbohydrate epitope specificity. Population II recognized epitopes containing phosphoethanolamine in zwitterionic and some acidic insect glycolipids. There are two subpopulations, the majority of which require the free amino group of phosphoethanolamine for immunoreactivity. Population III antibodies showed immunoreactivity to terminal beta-glucuronic acid-containing epitopes present only on acidic insect glycolipids.

Animals↗
PubMed2001

Insect symbiosis: derivation of yeast-like endosymbionts within an entomopathogenic filamentous lineage.

Yeast-like endosymbionts (YLSs) of insects often are restricted to specific hosts and are essential to the host's survival. For example, in planthoppers (Homoptera: Delphacidae), endosymbionts function in sterol utilization and nitrogen recycling for the hosts. Our study, designed to investigate evolutionary changes in the YLS lineage involved in the planthopper association, strongly suggests an origin of the YLSs from within the filamentous ascomycetes (Euascomycetes), not the true yeasts (Saccharomycetes), as their morphology might indicate. During divergence of the planthopper YLSs, dramatic changes would have occurred in the insect-fungus interaction and the fungal morphology that have previously been undescribed in filamentous ascomycetes. Phylogenetic trees were based on individual and combined data sets of 2.6 kb of the nuclear small- and large-subunit ribosomal RNA genes for YLSs from three rice planthoppers (Laodelphax striatellus, Nilaparvata lugens, and Sogatella furcifera) compared with 56 other fungi. Parsimony analysis placed the planthopper YLSs within Cordyceps (Euascomycetes: Hypocreales: Clavicipitaceae), a genus of filamentous insects and a few fungal pathogenic ascomycetes. Another YLS species restricted to the aphid Hamiltonaphis styraci (Homoptera: Aphididae) was a sister taxon to the planthopper YLSS: Filamentous insect pathogens (Metarhizium and Beauveria) specific to the same species of insect hosts as the YLSs also formed lineages within the Clavicipitaceae, but these were distinct from the clade comprising YLS species. Trees constrained to include the YLSs in families of the Hypocreales other than the Clavicipitaceae were rejected by the Kishino-Hasegawa test. In addition, the results of this study support a hypothesis of two independent origins of insect-associated YLSs from among filamentous ascomycetes: the planthopper YLSs in the Clavicipitaceae and the YLSs associated with anobiid beetles (Symbiotaphrina species). Several lineages of true yeasts (Saccharomycetes) also formed endosymbiotic associations with beetles, but they were not closely related to either group derived from the filamentous ascomycetes.

Animals↗
PubMed2001

Fruit or aposematic insect? Context-dependent colour preferences in domestic chicks.

Colours are common stimuli in signalling systems. Requirements to function well as a signal sometimes conflict between different signallers, and the same colour stimulus is used to convey completely different messages to the same receiver. Fruits and aposematic insects both use red coloration as a signal, in the former case to signal profitability and in the latter case as a warning signal. In two experiments, we investigated whether the domestic chick, an omnivorous predator, differed in its unconditioned preference or avoidance of red and green stimuli depending on whether or not the stimulus was an insect. The experiments were designed as preference tests between red and green painted prey. The prey were live insects and artificial fruits (experiment 1), and, to investigate the effect of movement, live and dead insects (experiment 2). The chicks did not show any difference in pecking preference between red and green when fruit-like stimuli were used, but when the prey were insects, green prey were strongly preferred to red prey, and prey movement did not affect this bias. Thus, young chicks may recognize prey as insects and then discriminate between different prey colorations, or one type of food may elicit an unlearned colour preference-avoidance response that is absent with another type of food.

Animals↗
PubMed2006

Cascading host-associated genetic differentiation in parasitoids of phytophagous insects.

The extraordinary diversity of phytophagous insects may be attributable to their narrow specialization as parasites of plants, with selective tradeoffs associated with alternate host plants driving genetic divergence of host-associated forms via ecological speciation. Most phytophagous insects in turn are attacked by parasitoid insects, which are similarly specialized and may also undergo host-associated differentiation (HAD). A particularly interesting possibility is that HAD by phytophagous insects might lead to HAD in parasitoids, as parasitoids evolve divergent lineages on the new host plant-specific lineages of their phytophagous hosts. We call this process 'cascading host-associated differentiation' (cascading HAD). We tested for cascading HAD in parasitoids of two phytophagous insects, each of which consists of genetically distinct host-associated lineages on the same pair of goldenrods (Solidago). Each parasitoid exhibited significant host-associated genetic divergence, and the distribution and patterns of divergence are consistent with divergence in sympatry. Although evidence for cascading HAD is currently limited, our results suggest that it could play an important role in the diversification of parasitoids attacking phytophagous insects. The existence of cryptic host-associated lineages also suggests that the diversity of parasitoids may be vastly underestimated.

Animals↗
PubMed2006

Evolution of long-range myofibrillar crystallinity in insect flight muscle as examined by X-ray cryomicrodiffraction.

Insect flight muscle is known for its crystal-quality regularity of contractile protein arrangement within a sarcomere. We have previously shown by X-ray microdiffraction that the crystal-quality regularity in bumble-bee flight muscle is not confined within a sarcomere, but extends over the entire length of a myofibril (>1000 sarcomeres connected in series). Because of this, the whole myofibril may be regarded as a millimetre-long, natural single protein crystal. Using bright X-ray beams from a synchrotron radiation source, we examined how this long-range crystallinity has evolved among winged insects. We analysed >4600 microdiffraction patterns of quick-frozen myofibrils from 50 insect species, covering all the major winged insect orders. The results show that the occurrence of such long-range crystallinity largely coincides with insect orders with asynchronous muscle operation. However, a few of the more skilled fliers among lower-order insects apparently have developed various degrees of structural regularity, suggesting that the demand for skillful flight has driven the lattice structure towards increased regularity.

Animals↗
PubMed2006

Medicago truncatula mutants demonstrate the role of plant calcium oxalate crystals as an effective defense against chewing insects.

Calcium oxalate is the most abundant insoluble mineral found in plants and its crystals have been reported in more than 200 plant families. In the barrel medic Medicago truncatula Gaertn., these crystals accumulate predominantly in a sheath surrounding secondary veins of leaves. Mutants of M. truncatula with decreased levels of calcium oxalate crystals were used to assess the defensive role of this mineral against insects. Caterpillar larvae of the beet armyworm Spodoptera exigua Hübner show a clear feeding preference for tissue from calcium oxalate-defective (cod) mutant lines cod5 and cod6 in choice test comparisons with wild-type M. truncatula. Compared to their performance on mutant lines, larvae feeding on wild-type plants with abundant calcium oxalate crystals suffer significantly reduced growth and increased mortality. Induction of wound-responsive genes appears to be normal in cod5 and cod6, indicating that these lines are not deficient in induced insect defenses. Electron micrographs of insect mouthparts indicate that the prismatic crystals in M. truncatula leaves act as physical abrasives during feeding. Food utilization measurements show that, after consumption, calcium oxalate also interferes with the conversion of plant material into insect biomass during digestion. In contrast to their detrimental effects on a chewing insect, calcium oxalate crystals do not negatively affect the performance of the pea aphid Acyrthosiphon pisum Harris, a sap-feeding insect with piercing-sucking mouthparts. The results confirm a long-held hypothesis for the defensive function of these crystals and point to the potential value of genes controlling crystal formation and localization in crop plants.

Animals↗
PubMed1997

Evidence for Chewing Insect-Specific Molecular Events Distinct from a General Wound Response in Leaves.

The timing of transcript accumulation of several wound-induced genes is different in insect-damaged and mechanically damaged leaves. Transcripts for the proteinase inhibitor II and 3-hydroxy-3-methylglutaryl-coenzyme A reductase genes accumulate more rapidly in potato (Solanum tuberosum L.) leaves chewed on by caterpillars than in leaves damaged mechanically. The timing of maximum transcript accumulation was not affected by the degree of damage inflicted by the insect larvae. When applied to a mechanical wound site, regurgitant isolated from Manduca sexta larvae causes transcript accumulation profiles to shift to parallel those in insect-damaged tissue. Whether obtained from larvae fed either potato leaves or a nonplant diet, insect regurgitant fed through the petiole of detached leaves also induces accumulation of these transcripts. The transcript accumulation-inducing activity of regurgitant is enhanced by heating at 100[deg]C. Our data suggest that a heat-stable, insect-derived elicitor functions to induce the rapid accumulation of transcripts that may be involved in plant defense against herbivores. Distinct signal transduction pathways that can distinguish between insect damage and abiotic damage might therefore exist in plants.

Journal Article↗
PubMed1993

Human beta 2-adrenergic receptor produced in stably transformed insect cells is functionally coupled via endogenous GTP-binding protein to adenylyl cyclase.

Spodoptera frugiperda insect cells (Sf9) containing the stably integrated human beta 2-adrenergic receptor gene under the control of the baculovirus IE1 promoter expressed up to 350,000 human receptors/cell. The number of receptors did not change with cell density or age of culture. The adrenergic receptors overexpressed in the insect cells were functional with respect to their ligand binding and signalling properties. Coupling of the receptors to endogenous GTP-binding proteins is demonstrated by hormone-dependent stimulation of GTPase and adenylyl cyclase activity in the transformed insect cells. Western-blot analysis revealed that the endogenous GTP-binding protein appears to be of the heterotrimeric type. Antibodies raised against the mammalian alpha subunit of stimulatory GTP-binding proteins cross-react with the insect alpha subunit of GTP-binding proteins, which also exhibits the same apparent molecular mass as its mammalian counterpart. The beta subunit of GTP-binding proteins from insect cells reacts with anti-peptide serum directed against the C-terminal amino acids of the mammalian beta subunit of GTP-binding proteins, but is about approximately 2 kDa larger than that of the beta subunit of GTP-binding proteins from bovine brain. Exposure of the transformed insect cells to L-isoproterenol rapidly induces uncoupling and internalization of 30% of the heterologously expressed receptors. In contrast to the situation in mammalian cells, prolonged exposure of the agonist (24 h) does not result in down regulation of the remaining 70% of the receptors.

Adenylyl Cyclases↗
PubMed1997

Anti-insect toxin 5 (AaIT5) from Androctonus australis.

An insect-selective scorpion toxin (AaIT5) was purified from the venom of the North African scorpion Androctonus australis, and its amino acid sequence was determined by a combination of automated Edman degradation, electrospray-ionization mass spectrometry, and sequence alignment. This insect toxin is very potent against the tobacco budworm, Heliothis virescens (100% lethal dose < 1.8 microg/100 mg body mass) and shows a distinct insect specificity and various symptoms. It is not toxic to mice after subcutaneous injection. The molecular mass of this toxin is 6882 Da and the amino acid sequence is similar to those of Androctonus australis anti-insect toxin 4 (AaIT4), Leiurus quinquestriatus depressant anti-insect toxins (LqhIT2, LqqIT2), and Buthotus judaicus depressant anti-insect toxin (BjIT2).

Amino Acid Sequence↗
PubMed2005

The efficacy of a novel insecticidal protein, Allium sativum leaf lectin (ASAL), against homopteran insects monitored in transgenic tobacco.

The homopteran group of polyphagous sucking insect pests causes severe damage to many economically important plants including tobacco. Allium sativum leaf lectin (ASAL), a mannose-binding 25-kDa homodimeric protein, has recently been found to be antagonistic to various sucking insects in the homopteran group through artificial diet bioassay experiments. The present study describes, for the first time, the expression of the ASAL coding sequence under the control of the cauliflower mosaic virus (CaMV) 35S promoter in tobacco by Agrobacterium-mediated transformation technology. Molecular analyses demonstrated the integration of the chimeric ASAL gene in tobacco and its inheritance in the progeny plants. Western blot analysis followed by enzyme-linked immunosorbent assay (ELISA) determined the level of ASAL expression in different lines to be in the range of approximately 0.68%-2% of total soluble plant protein. An in planta bioassay conducted with Myzus persicae, peach potato aphid (a devastating pest of tobacco and many other important plants), revealed that the percentage of insect survival decreased significantly to 16%-20% in T0 plants and T1 progeny, whilst approximately 75% of insects survived on untransformed tobacco plants after 144 h of incubation. Ligand analyses of insect brush border membrane vesicle receptors and expressed ASAL in transgenic tobacco showed that the expressed ASAL binds to the aphid gut receptor in the same manner as native ASAL, pointing to the fact that ASAL maintains the biochemical characteristics even in the transgenic situation. These findings in a model plant open up the possibility of expressing the novel ASAL gene in a wide range of crop plants susceptible to various sap-sucking insects.

Journal Article↗
PubMed2006

The evolution of plant-insect mutualisms.

Mutualisms (cooperative interactions between species) have had a central role in the generation and maintenance of life on earth. Insects and plants are involved in diverse forms of mutualism. Here we review evolutionary features of three prominent insect-plant mutualisms: pollination, protection and seed dispersal. We focus on addressing five central phenomena: evolutionary origins and maintenance of mutualism; the evolution of mutualistic traits; the evolution of specialization and generalization; coevolutionary processes; and the existence of cheating. Several features uniting very diverse insect-plant mutualisms are identified and their evolutionary implications are discussed: the involvement of one mobile and one sedentary partner; natural selection on plant rewards; the existence of a continuum from specialization to generalization; and the ubiquity of cheating, particularly on the part of insects. Plant-insect mutualisms have apparently both arisen and been lost repeatedly. Many adaptive hypotheses have been proposed to explain these transitions, and it is unlikely that any one of them dominates across interactions differing so widely in natural history. Evolutionary theory has a potentially important, but as yet largely unfilled, role to play in explaining the origins, maintenance, breakdown and evolution of insect-plant mutualisms.

Animals↗