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Jasmonoyl-L-isoleucine hydrolase 1 (JIH1) regulates jasmonoyl-L-isoleucine levels and attenuates plant defenses against herbivores
Woldemariam, M.G. ; Onkokesung, N. ; Baldwin, I.T. ; Galis, I. - \ 2012
The Plant Journal 72 (2012)5. - ISSN 0960-7412 - p. 758 - 767.
agrobacterium-mediated transformation - auxin conjugate hydrolase - nicotiana-attenuata - manduca-sexta - proteinase-inhibitors - arabidopsis-thaliana - insect herbivores - acid - responses - family
For most plant hormones, biological activity is suppressed by reversible conjugation to sugars, amino acids and other small molecules. In contrast, the conjugation of jasmonic acid (JA) to isoleucine (Ile) is known to enhance the activity of JA. Whereas hydroxylation and carboxylation of JA-Ile permanently inactivates JA-Ilemediated signaling in plants, the alternative deactivation pathway of JA-Ile by its direct hydrolysis to JA remains unstudied. We show that Nicotiana attenuata jasmonoyl-L-isoleucine hydrolase 1 (JIH1), a close homologue of previously characterized indoleacetic acid alanine resistant 3 (IAR3) gene in Arabidopsis, hydrolyzes both JA-Ile and IAA-Ala in vitro. When the herbivory-inducible NaJIH1 gene was silenced by RNA interference, JA-Ile levels increased dramatically after simulated herbivory in irJIH1, compared with wild-type (WT) plants. When specialist (Manduca sexta) or generalist (Spodoptera littoralis) herbivores fed on irJIH1 plants they gained significantly less mass compared with those feeding on wild-type (WT) plants. The poor larval performance was strongly correlated with the higher accumulation of several JA-Ile-dependent direct defense metabolites in irJIH1 plants. In the field, irJIH1 plants attracted substantially more Geocoris predators to the experimentally attached M. sexta eggs on their leaves, compared with empty vector plants, which correlated with higher herbivory-elicited emissions of volatiles known to function as indirect defenses. We conclude that NaJIH1 encodes a new homeostatic step in JA metabolism that, together with JA and JA-Ilehydroxylation and carboxylation of JA-Ile, rapidly attenuates the JA-Ile burst, allowing plants to tailor the expression of direct and indirect defenses against herbivore attack in nature.
RNA interference in Lepidoptera: An overview of successful and unsuccessful
Terenius, O. ; Papanicolaou, A. ; Garbutt, J.S. ; Eleftherianos, I. ; Huvenne, H. ; Kanginakudru, S. ; Albrechtsen, M. ; An, Chunju ; Aymeric, J.L. ; Barthel, A. ; Bebas, P. ; Bitra, K. ; Bravo, A. ; Chevalier, F. ; Collinge, D.P. ; Crava, C.M. ; Maagd, R.A. de; Duvic, B. ; Erlandson, M. ; Faye, I. ; Felfoldi, G. ; Fujiwara, H. ; Futahashi, R. ; Gandhe, A.S. ; Gatehouse, H.S. ; Gatehouse, L.N. ; Giebultowicz, J.M. ; Gomez, I. ; Grimmelikhuijzen, C.J.P. ; Groot, A.T. ; Hauser, F. ; Heckel, D.G. ; Hegedus, D.D. ; Hrycaj, S. ; Huang, L. ; Hull, J.J. ; Iatrou, K. ; Iga, M. ; Kanost, M.R. ; Kotwica, J. ; Li, Changyou ; Li, Jianghong ; Liu, Jisheng ; Lundmark, M. ; Matsumoto, S. ; Meyering-Vos, M. ; Millichap, P.J. ; Monteiro, A. ; Mrinal, N. ; Niimi, T. ; Nowara, D. ; Ohnishi, A. ; Oostra, V. ; Ozaki, K. ; Papakonstantinou, M. ; Popadic, A. ; Rajam, M.V. ; Saenko, S. ; Simpson, R.M. ; Soberon, M. ; Strand, M.R. ; Tomita, S. ; Toprak, U. ; Wang, Ping ; Wee, Choon Wei ; Whyard, S. ; Zhang, Wenqing ; Nagaraju, J. ; Ffrench-Constant, R.H. ; Herrero, S. ; Gordon, K. ; Swevers, L. ; Smagghe, G. - \ 2011
Journal of Insect Physiology 57 (2011)2. - ISSN 0022-1910 - p. 231 - 245.
double-stranded-rna - armyworm spodoptera-frugiperda - silkworm bombyx-mori - small silencing rnas - manduca-sexta - bacillus-thuringiensis - caenorhabditis-elegans - helicoverpa-armigera - immune-responses - messenger-rna
Gene silencing through RNA interference (RNAi) has revolutionized the study of gene function, particularly in non-model insects. However, in Lepidoptera (moths and butterflies) RNAi has many times proven to be difficult to achieve. Most of the negative results have been anecdotal and the positive experiments have not been collected in such a way that they are possible to analyze. In this review, we have collected detailed data from more than 150 experiments including all to date published and many unpublished experiments. Despite a large variation in the data, trends that are found are that RNAi is particularly successful in the family Saturniidae and in genes involved in immunity. On the contrary, gene expression in epidermal tissues seems to be most difficult to silence. In addition, gene silencing by feeding dsRNA requires high concentrations for success. Possible causes for the variability of success in RNAi experiments in Lepidoptera are discussed. The review also points to a need to further investigate the mechanism of RNAi in lepidopteran insects and its possible connection to the innate immune response. Our general understanding of RNAi in Lepidoptera will be further aided in the future as our public database at http://insectacentral.org/RNAi will continue to gather information on RNAi experiments
Dominant negative phenotype of Bacillus thuringiensis Cry1Ab, Cry11Aa and Cry4Ba mutants suggest hetero-oligomer formation among different Cry toxins.
Carmona, D. ; Rodriguez-Almazan, C. ; Munoz-Garay, C. ; Portugal, L. ; Perez, C. ; Maagd, R.A. de; Bakker, P. ; Soberon, M. ; Bravo, A. - \ 2011
PLoS One 6 (2011)5. - ISSN 1932-6203 - 6 p.
subsp israelensis - delta-endotoxin - manduca-sexta - alkaline-phosphatase - protective antigen - anopheles-gambiae - toxicity - crystal - anthrax - mutagenesis
Background - Bacillus thuringiensis Cry toxins are used worldwide in the control of different insect pests important in agriculture or in human health. The Cry proteins are pore-forming toxins that affect the midgut cell of target insects. It was shown that non-toxic Cry1Ab helix a-4 mutants had a dominant negative (DN) phenotype inhibiting the toxicity of wildtype Cry1Ab when used in equimolar or sub-stoichiometric ratios (1:1, 0.5:1, mutant:wt) indicating that oligomer formation is a key step in toxicity of Cry toxins. Methodology/Principal Findings - The DN Cry1Ab-D136N/T143D mutant that is able to block toxicity of Cry1Ab toxin, was used to analyze its capacity to block the activity against Manduca sexta larvae of other Cry1 toxins, such as Cry1Aa, Cry1Ac, Cry1Ca, Cry1Da, Cry1Ea and Cry1Fa. Cry1Ab-DN mutant inhibited toxicity of Cry1Aa, Cry1Ac and Cry1Fa. In addition, we isolated mutants in helix a-4 of Cry4Ba and Cry11Aa, and demonstrate that Cry4Ba-E159K and Cry11Aa-V142D are inactive and completely block the toxicity against Aedes aegypti of both wildtype toxins, when used at sub-stoichiometric ratios, confirming a DN phenotype. As controls we analyzed Cry1Ab-R99A or Cry11Aa-E97A mutants that are located in helix a-3 and are affected in toxin oligomerization. These mutants do not show a DN phenotype but were able to block toxicity when used in 10:1 or 100:1 ratios (mutant:wt) probably by competition of binding with toxin receptors. Conclusions/Significance - We show that DN phenotype can be observed among different Cry toxins suggesting that may interact in vivo forming hetero-oligomers. The DN phenotype cannot be observed in mutants affected in oligomerization, suggesting that this step is important to inhibit toxicity of other toxins
Constitutive Activation of the Midgut Response to Bacillus thuringiensis in Bt-Resistant Spodoptera exigua
Hernandez-Martinez, P. ; Navarro-Cerrillo, G. ; Caccia, S. ; Maagd, R.A. de; Moar, W.J. ; Ferre, J. ; Escriche, B. ; Herrero, S. - \ 2010
PLoS One 5 (2010)9. - ISSN 1932-6203
mediated insect resistance - stem-cell proliferation - heliothis-virescens - manduca-sexta - bacterial-infection - posterior midgut - crystal proteins - aminopeptidase n - kinase pathways - trichoplusia-ni
Bacillus thuringiensis is the most effective microbial control agent for controlling numerous species from different insect orders. The main threat for the long term use of B. thuringiensis in pest control is the ability of insects to develop resistance. Thus, the identification of insect genes involved in conferring resistance is of paramount importance. A colony of Spodoptera exigua (Lepidoptera: Noctuidae) was selected for 15 years in the laboratory for resistance to Xentari (TM), a B. thuringiensis-based insecticide, reaching a final resistance level of greater than 1,000-fold. Around 600 midgut ESTs were analyzed by DNA-macroarray in order to find differences in midgut gene expression between susceptible and resistant insects. Among the differentially expressed genes, repat and arylphorin were identified and their increased expression was correlated with B. thuringiensis resistance. We also found overlap among genes that were constitutively over-expressed in resistant insects with genes that were up-regulated in susceptible insects after exposure to Xentari (TM), suggesting a permanent activation of the response to Xentari (TM) in resistant insects. Increased aminopeptidase activity in the lumen of resistant insects in the absence of exposure to Xentari (TM) corroborated the hypothesis of permanent activation of response genes. Increase in midgut proliferation has been proposed as a mechanism of response to pathogens in the adult from several insect species. Analysis of S. exigua larvae revealed that midgut proliferation was neither increased in resistant insects nor induced by exposure of susceptible larvae to Xentari (TM), suggesting that mechanisms other than midgut proliferation are involved in the response to B. thuringiensis by S. exigua larvae.
Intraspecific variation in herbivore community composition and transcriptional profiles in field-grown Brassica oleracea cultivars
Broekgaarden, C. ; Poelman, E.H. ; Voorrips, R.E. ; Dicke, M. ; Vosman, B. - \ 2010
Journal of Experimental Botany 61 (2010)3. - ISSN 0022-0957 - p. 807 - 819.
induced plant vaccination - 2 specialist herbivores - mustard oil bomb - nicotiana-attenuata - induced resistance - microarray analysis - jasmonic acid - manduca-sexta - brevicoryne-brassicae - insect resistance
Intraspecific differences in plant defence traits are often correlated with variation in transcriptional profiles and can affect the composition of herbivore communities on field-grown plants. However, most studies on transcriptional profiling of plant–herbivore interactions have been carried out under controlled conditions in the laboratory or greenhouse and only a few examine intraspecific transcriptional variation. Here, intraspecific variation in herbivore community composition and transcriptional profiles between two Brassica oleracea cultivars grown in the field is addressed. Early in the season, no differences in community composition were found for naturally occurring herbivores, whereas cultivars differed greatly in abundance, species richness, and herbivore community later in the season. Genome-wide transcriptomic analysis using an Arabidopsis thaliana oligonucleotide microarray showed clear differences for the expression levels of 26 genes between the two cultivars later in the season. Several defence-related genes showed higher levels of expression in the cultivar that harboured the lowest numbers of herbivores. Our study shows that herbivore community composition develops differentially throughout the season on the two B. oleracea cultivars grown in the field. The correlation between the differences in herbivore communities and differential expression of particular defence-related genes is discussed.
Effects of dietary nicotine on the development of an insect herbivore, its parasitoid and secondary hyperparasitoid over four trophic levels
Harvey, J.A. ; Dam, N.M. van; Witjes, L.M.A. ; Soler, R. ; Gols, R. - \ 2007
Ecological Entomology 32 (2007)q. - ISSN 0307-6946 - p. 15 - 23.
host-plant chemistry - manduca-sexta - cotesia-congregata - specialist herbivore - hyposoter-annulipes - tobacco hornworm - natural enemies - allelochemicals - hymenoptera - performance
1. Allelochemicals in herbivore diet are known to affect the development of higher trophic levels, such as parasitoids and predators. 2. This study examines how differing levels of nicotine affects the development of a herbivore, its parasitoid and secondary hyperparasitoid over four trophic levels. Separate cohorts of the herbivore, Manduca sexta, were fed on artificial diets containing 0.0, 0.1, and 0.5% wet weights of nicotine. Some of the larvae in each cohort were separately parasitised in the first (L1) and third (L3) instars by the gregarious endoparasitoid, Cotesia congregata. Newly emerged parasitoid cocoons were, in turn, parasitised by the hyperparasitoid, Lysibia nana. 3. Pupal mass in M. sexta was negatively correlated with nicotine concentrations in the artificial diet, although larval development time was unaffected. 4. Hyperparasitoid survival was highest when there were low levels of nicotine in the diet of M. sexta. Cocoon mass in C. congregata and adult mass in L. nana were mostly affected by nicotine levels in host diet when L1 M. sexta larvae were parasitised. The effects were slightly stronger on L. nana than on C. congregata, indicating the presence of both qualitative and quantitative effects of nicotine concentration on both species. 5. The results suggest that allelochemicals in herbivore diet can have both direct and indirect effects on the performance of higher trophic levels. However, in multitrophic interactions these effects can vary with the stage of the herbivore attacked by the primary parasitoid, as well as with the strategy employed by the herbivore to deal with plant phytotoxins.
Development of an insect herbivore and its pupal parasitoid reflect differences in direct plant defense
Harvey, J.A. ; Gols, R. ; Wagenaar, R. ; Bezemer, T.M. - \ 2007
Journal of Chemical Ecology 33 (2007)8. - ISSN 0098-0331 - p. 1556 - 1569.
4 trophic levels - host-plant - specialist herbivore - phytophagous insects - plutella-xylostella - brassica-oleracea - wild populations - trichoplusia-ni - manduca-sexta - pieris-rapae
In nature, plants defend themselves by production of allelochemicals that are toxic to herbivores. There may be considerable genetic variation in the expression of chemical defenses because of various selection pressures. In this study, we examined the development of the small cabbage butterfly, Pieris rapae, and its gregarious pupal ectoparasitoid, Pteromalus puparum, when reared on three wild populations (Kimmeridge, Old Harry, Winspit) of cabbage, Brassica oleracea, and a Brussels sprout cultivar. Wild plant populations were obtained from seeds of plants that grow naturally along the south coast of Dorset, England. Significant differences in concentrations of allelochemicals (glucosinolates) were found in leaves of plants damaged by P. rapae. Total glucosinolate concentrations in Winspit plants, the population with the highest total glucosinolate concentration, were approximately four times higher than in the cultivar, the strain with the lowest total glucosinolate concentration. Pupal mass of P. rapae and adult body mass of Pt. puparum were highest when reared on the cultivar and lowest when developing on Kimmeridge plants, the wild strain with the lowest total glucosinolate concentration. Development of male parasitoids was also more negatively affected than female parasitoids. Our results reveal that plant quality, at least for the development of 'adapted' oligophagous herbivores, such as P. rapae, is not based on total glucosinolate content. The only glucosinolate compound that corresponded with the performance of P. rapae was the indole glucosinolate, neoglucobrassicin. Our results show that performance of ectoparasitoids may closely reflect constraints on the development of the host.
The remarkable conservation of corticotropin-releasing hormone (CRH)-binding protein in the honeybee (Apis mellifera) dates the CRH system to a common ancestor of insects and vertebrates
Huising, M.O. ; Flik, G. - \ 2005
Endocrinology 146 (2005)5. - ISSN 0013-7227 - p. 2165 - 2170.
factor-binding-protein - diuretic hormone - biochemical-characterization - divergence time - manduca-sexta - urotensin-i - ligand - stress - neuropeptides - pharmacology
CRH-binding protein (CRH-BP) is a key factor in the regulation of CRH signaling; it modulates the bioactivity and bioavailability of CRH and its related peptides. The conservation of CRH-BP throughout vertebrates was only recently demonstrated. Here we report the presence of CRH-BP in the honeybee (Apis mellifera) and other insects. Honeybee CRH-BP resembles previously characterized vertebrate CRH-BP sequences with respect to conserved cysteine residues, gene organization, and overall sequence identity. Phylogenetic analyses confirm the unambiguous orthology of insect and vertebrate CRH-BP sequences. Soon after their discovery, it was noted that insect diuretic hormone-I (DH-I) and its receptor share similarities with the vertebrate CRH family and their receptors. Despite these similarities, demonstration of common ancestry of DH-I and the vertebrate CRH family is still speculative: the mature neuropeptides are short, and their genes differ substantially with regard to the number of coding exons. Moreover, DH and CRH receptors belong to the much larger family of G protein-coupled receptors. In contrast, the unique and conspicuous features of CRH-BP greatly facilitate the establishment of orthology over much larger evolutionary distances. The identification of CRH-BP in insects clearly indicates that this gene predates vertebrates by at least several hundred million years. Moreover, our findings imply that a CRH system is shared by insects and vertebrates alike and, consequently, that it has been present at least since the common ancestor to both phylogenetic lines of proto- and deuterostomians.
Identification and recombinant expression of a novel chymotrypsin from Spodoptera exigua
Herrero, S. ; Combes, E. ; Oers, M.M. van; Vlak, J.M. ; Maagd, R.A. de; Beekwilder, M.J. - \ 2005
Insect Biochemistry and Molecular Biology 35 (2005)10. - ISSN 0965-1748 - p. 1073 - 1082.
bacillus-thuringiensis toxins - helicoverpa-zea - proteinase-inhibitors - trypsin-inhibitor - agrotis-ipsilon - manduca-sexta - midgut - proteases - sequence - larvae
A novel chymotrypsin which is expressed in the midgut of the lepidopteran insect Spodoptera exigua is described. This enzyme, referred to as SeCT34, represents a novel class of chymotrypsins. Its amino-acid sequence shares common features of gut chymotrpysins, but can be clearly distinguished from other serine proteinases that are expressed in the insect gut. Most notable, SeCT34 contains a chymotrypsin activation site and the highly conserved motive DSGGP in the catalytic domain around the active-site serine is changed to DSGSA. Recombinant expression of SeCT34 was achieved in Sf21 insect cells using a special baculovirus vector, which has been engineered for optimized protein production. This is the first example of recombinant expression of an active serine proteinase which functions in the lepidopteran digestive tract. Purified recombinant SeCT34 enzyme was characterized by its ability to hydrolyze various synthetic substrates and its susceptibility to proteinase inhibitors. It appeared to be highly selective for substrates carrying a phenylalanine residue at the cleavage site. SeCT34 showed a pH-dependence and sensitivity to inhibitors, which is characteristic for semi-purified lepidopteran gut proteinases. Expression analysis revealed that SeCT34 was only expressed in the midgut of larvae at the end of their last instar, just before the onset of pupation. This suggests a possible role of this protein in the proteolytic remodelling that occurs in the gut during the larval to pupal molt.
Bacillus thuringiensis Cry1Ca-resistant Spodoptera exigua lacks expression of one of four Aminopeptidase N genes
Herrero, S. ; Gechev, T. ; Bakker, P.L. ; Moar, W. ; Maagd, R.A. de - \ 2005
BMC Genomics 6 (2005). - ISSN 1471-2164 - p. 96 - 96.
brush-border membrane - delta-endotoxin - manduca-sexta - bombyx-mori - heliothis-virescens - plutella-xylostella - molecular-cloning - toxin receptor - cry1a toxins - midgut
BACKGROUND: Insecticidal toxins from Bacillus thuringiensis bind to receptors on midgut epithelial cells of susceptible insect larvae. Aminopeptidases N (APNs) from several insect species have been shown to be putative receptors for these toxins. Here we report the cloning and expression analysis of four APN cDNAs from Spodoptera exigua. RESULTS: Suppression Subtractive Hybridization (SSH) was used to construct cDNA libraries of genes that are up- and down-regulated in the midgut of last instar larvae of beet armyworm, S. exigua exposed to B. thuringiensis Cry1Ca toxin. Among the clones from the SSH libraries, cDNA fragments coding for two different APNs were obtained (APN2 and APN4). A similar procedure was employed to compare mRNA differences between susceptible and Cry1Ca resistant S. exigua. Among the clones from this last comparison, cDNA fragments belonging to a third APN (APN1) were detected. Using sequences obtained from the three APN cDNA fragments and degenerate primers for a fourth APN (APN3), the full length sequences of four S. exigua APN cDNAs were obtained. Northern blot analysis of expression of the four APNs showed complete absence of APN1 expression in the resistant insects, while the other three APNs showed similar expression levels in the resistant and susceptible insects. CONCLUSIONS: We have cloned and characterized four different midgut APN cDNAs from S. exigua. Expression analysis revealed the lack of expression of one of these APNs in the larvae of a Cry1Ca-resistant colony. Combined with previous evidence that shows the importance of APN in the mode of action of B. thuringiensis toxins, these results suggest that the lack of APN1 expression plays a role in the resistance to Cry1Ca in this S. exigua colony
Root herbivory reduces growth and survival of the shoot feeding specialist Pieris rapae on Brassica nigra
Dam, N.M. van; Raaijmakers, C.E. ; Putten, W.H. van der - \ 2005
Entomologia Experimentalis et Applicata 115 (2005)1. - ISSN 0013-8703 - p. 161 - 170.
plant-mediated interactions - meloidogyne-incognita - black mustard - manduca-sexta - defense - tobacco - glucosinolate - induction - quality - fly
Plants may respond to herbivore attacks by changing their chemical profile. Such induced responses occur both locally and systemically throughout the plant. In this paper we studied how Brassica nigra (L.) Koch (Brassicaceae) plants respond to two different root feeders, the endoparasitic nematode Pratylenchus penetrans Cobb (Tylenchida: Pratylenchidae) and the larvae of the cabbage root fly Delia radicum L. (Diptera: Anthomyiidae). We tested whether the activities of the root feeders affected the survival and development of the shoot feeding crucifer specialist Pieris rapae (L.) (Lepidoptera: Pieridae) via systemically induced changes in the shoots. Overall, P. rapae larvae grew slower and produced fewer pupae on plants that were infested with root feeders, especially on plants infested with P. penetrans. This effect could not be attributed to lower water or protein levels in these plants, as the percentage of water in the controls and root infested shoots was similar, and protein content was even higher in root infested plants. Both glucosinolate as well as phenolic levels were affected by root feeding. Initially, glucosinolate levels were the lowest in root infested plants, but on P. penetrans infested plants they increased more rapidly after P. rapae started feeding than in controls or D. radicum infested plants. Plants with D. radicum feeding on their roots had the highest phenolic levels at all harvest dates. Our results indicate that root feeding can significantly alter the nutritional quality of shoots by changes in secondary metabolite levels and hence the performance of a specialist shoot feeder
Mutations in the Bacillus thuringiensis Cry1Ca toxin demonstrate the role of domain II and III in the specificity towards Spodoptera exigua larvae
Herrero Sendra, S. ; González-Cabrera, J. ; Ferré, J. ; Bakker, P.L. ; Maagd, R.A. de - \ 2004
Biochemical Journal 384 (2004)3. - ISSN 0264-6021 - p. 507 - 513.
brush-border membrane - cryia delta-endotoxins - manduca-sexta - crystal proteins - aminopeptidase n - irreversible binding - heliothis-virescens - insecticidal toxin - pore formation - pink-bollworm
Several mutants of the Bacillus thuringiensis Cry1Ca toxin affected with regard to specific activity towards Spodoptera exigua were studied. Alanine was used to replace single residues in loops 2 and 3 of domain II (mutant pPB19) and to replace residues 541-544 in domain III (mutant pPB20). Additionally, a Cry1Ca mutant combining all mutations was constructed (mutant pPB21). Toxicity assays showed a marked decrease in toxicity against S. exigua for all mutants, while they retained their activity against Manduca sexta, confirming the importance of these residues in determining insect specificity. Parameters for binding to the specific receptors in BBMV (brush border membrane vesicles) of S. exigua were determined for all toxins. Compared with Cry1Ca, the affinity of mutant pPB19 was slightly affected (2-fold lower), whereas the affinity of the mutants with an altered domain III (pPB20 and pPB21) was approx. 8-fold lower. Activation of Cry1Ca protoxin by incubation with S. exigua or M. sexta BBMV revealed the transient formation of an oligomeric form of Cry1Ca. The presence of this oligomeric form was tested in the activation of the different Cry1Ca mutants, and we found that those mutated in domain II (pPB19 and pPB21) could not generate the oligomeric form when activated by S. exigua BBMV. In contrast, when oligomerization was tested using BBMV prepared from M. sexta, all of the Cry1Ca mutants showed the formation of a similar oligomeric form as did the wild-type toxin. Our results show how modification of insect specificity can be achieved by manipulation of different parts of the toxin structure involved in different steps of the mode of action of B. thuringiensis toxins
Central projections of olfactory receptor neurons from single antennal and palpal sensilla in mosquitoes
Anton, S. ; Loon, J.J.A. van; Meijerink, J. ; Smid, H.M. ; Takken, W. ; Rospars, J.P. - \ 2003
Arthropod Structure & Development 32 (2003). - ISSN 1467-8039 - p. 319 - 327.
aedes-aegypti - anopheles-gambiae - malaria mosquito - lactic-acid - drosophila-melanogaster - maxillary palp - electrophysiological responses - manduca-sexta - sensory map - fly brain
In insects, olfactory receptor neurons (ORNs) are located in cuticular sensilla, that are present on the antennae and on the maxillary palps. Their axons project into spherical neuropil, the glomeruli, which are characteristic structures in the primary olfactory center throughout the animal kingdom. ORNs in insects often respond specifically to single odor compounds. The projection patterns of these neurons within the primary olfactory center, the antennal lobe, are, however, largely unknown. We developed a method to stain central projections of intact receptor neurons known to respond to host odor compounds in the malaria mosquito, Anopheles gambiae. Terminal arborizations from ORNs from antennal sensilla had only a few branches apparently restricted to a single glomerulus. Axonal arborizations of the different neurons originating from the same sensillum did not overlap. ORNs originating from maxillary palp sensilla all projected into a dorso-medial area in both the ipsi- and contralateral antennal lobe, which received in no case axon terminals from antennal receptor neurons. Staining of maxillary palp receptor neurons in a second mosquito species (Aedes aegypti) revealed unilateral arborizations in an area at a similar position as in An. gambiae. (C) 2003 Elsevier Ltd. All rights reserved.
Induction of direct and indirect plant responses by jasmonic acid, low spider mite densities, or a combination of jasmonic acid treatment and spider mite infestation
Gols, G.J.Z. ; Roosjen, M. ; Dijkman, H. ; Dicke, M. - \ 2003
Journal of Chemical Ecology 29 (2003)12. - ISSN 0098-0331 - p. 2651 - 2666.
herbivore-induced plant - tetranychus-urticae - phytoseiulus-persimilis - nicotiana-attenuata - biological-control - induced volatiles - beta-glucosidase - parasitic wasps - predatory mites - manduca-sexta
Jasmonic acid (JA) and the octadecanoid pathway are involved in both induced direct and induced indirect plant responses. In this study, the herbivorous mite, Tetranychus urticae, and its predator, Phytoseiulus persimilis, were given a choice between Lima bean plants induced by JA or spider mites and uninduced control plants. Infestation densities resulting in the induction of predator attractants were much lower than thus far assumed, i.e., predatory mites were significantly attracted to plants that were infested for 2 days with only one or four spider mites per plant. Phytoseiulus persimilis showed a density-dependent response to volatiles from plants that were infested with different numbers of spider mites. Similarly, treating plants with increasing concentrations of JA also led to increased attraction of P. persimilis. Moreover, the duration of spider mite infestation was positively correlated with the proportion of predators that were attracted to mite-infested plants. A pretreatment of the plants with JA followed by a spider mite infestation enhanced the attraction of P. persimilis to plant volatiles compared to attraction to volatiles from plants that were only infested with spider mites and did not receive a pretreatment with JA. The herbivore, T. urticae preferred leaf tissue that previously had been infested with conspecifics to uninfested leaf tissue. In the case of choice tests with JA-induced and control leaf tissue, spider mites slightly preferred control leaf tissue. When spider mites were given a choice between leaf discs induced by JA and leaf discs damaged by spider mite feeding, they preferred the latter. The presence of herbivore induced chemicals and/or spider mite products enhanced settlement of the mites, whereas treatment with JA seemed to impede settlement.
Interactions over four trophic levels: foodplant quality affects development of a hyperparasitoid as mediated through a herbivore and its primary parasitoid
Harvey, J.A. ; Dam, N.M. van; Gols, G.J.Z. - \ 2003
Journal of Animal Ecology 72 (2003). - ISSN 0021-8790 - p. 520 - 531.
host quality - phytophagous insects - repellent defenses - natural enemies - brassica-napus - manduca-sexta - plant - growth - glucosinolate - hymenoptera
1. Related plant species with different spatial and/or temporal life-history characteristics often possess differences in secondary chemistry and thus direct defensive capability. These differences are often attributed to a range of divergent selection pressures from herbivores and pathogens. Most studies of insect-plant interactions have examined the effects of plant defence on herbivore performance, with less attention being paid to higher trophic levels, such as parasitoid wasps. Moreover, to date it is not known whether secondary plant compounds may affect organisms in the fourth trophic level. 2. Here, we study interactions in a four-trophic-level system. The development of a solitary secondary hyperparasitoid, Lysibia nana , and its primary endoparasitoid host, Cotesia glomerata , are compared when reared from a primary herbivore host, Pieris brassicae, which was itself reared on two cruciferous plants with contrasting life histories. Whereas L. nana is known to attack the pupae of a number of primary parasitoids in the genus Cotesia , both C. glomerata and P. brassicae are intimately associated with plants in the family Brassicaceae. 3. Insects were reared from a feral population of the spring perennial, Brassica oleracea , and a naturally occurring population of a summer annual, B. nigra . Like other cruciferous plants, both species are known to produce glycoside toxins (= glucosinolates) after they are attacked by foliar herbivores. However, concentrations of glucosinolates were more than 3.5 times higher in young shoots of B. nigra than in corresponding shoots of B. oleracea . 4. Cocoon weight in C. glomerata was unaffected by the foodplant on which P. brassicae was reared, whereas in 24-h-old host cocoons emerging adult hyperparasitoid body mass increased significantly with cocoon size and wasps were significantly larger, and survived better on B. oleracea than on B. nigra. Moreover, body mass in L. nana was typically larger in young (c. 24 h), than in older (c. 72 h) cocoons of C. glomerata. Egg-to-adult development time in L. nana generally increased with host size and age, and wasps on younger hosts completed their development more rapidly on B. nigra. 5. Our results clearly demonstrate that qualitative differences in herbivore diet can differently affect the performance of interacting organisms across several trophic levels, and suggest that bottom-up forces may also play a role in mediating interactions involving plants-herbivores-parasitoids and hyperparasitoids.
Differences among plant species in acceptance by the spider mite Tetranychus urticae Koch
Boom, C.E.M. van den; Beek, T.A. van; Dicke, M. - \ 2003
Journal of Applied Entomology 127 (2003)3. - ISSN 0931-2048 - p. 177 - 183.
phytophagous mite - manduca-sexta - host - acari - resistance - phytoseiidae - lepidoptera - population - induction - selection
The spider mite Tetranychus urticae Koch has a broad range of host plants. However, the spider mite does not accept all plants to the same degree because of differences in nutritive and toxic constituents. Other factors, such as the induction of secondary metabolites, the morphology of a leaf surface and the presence of natural enemies, also play an important role in plant acceptance. We compared plants from various families in their degree of acceptance by the spider mite, to get an indication of the plant's direct defence. Glycine max (soybean), Humulus lupulus (hop), Laburnum anagyroides (golden chain) and Nicotiana tabacum (tobacco) were highly accepted by the spider mites. Different glandular hair densities among tobacco cultivars did not affect their suitability towards spider mites significantly. Solanum melalonga (eggplant), Robinia pseudo-acacia (black locust), Vigna unguiculata (cowpea) and Datura stramonium (thorn apple) were accepted by the spider mites to a lesser degree. Vitis vinifera (grapevine) was poorly accepted by the spider mite. It might be that the food quality of the leaves was not high enough to arrest the spider mites. Also, Capsicum annuum (sweet pepper) and especially Ginkgo biloba (ginkgo) were poorly accepted by the spider mite, probably because of the presence and concentration of certain of the secondary metabolites in the leaves. The spider mites accepted all the plants belonging to the Fabaceae for feeding, but those belonging to the Solanaceae showed a larger variance in spider mite acceptance varying from well accepted (tobacco) to poorly accepted (sweet pepper).
Properties of purified gut trypsin from Helicoverpa zea, adapted to to proteinase inhibitors.
Volpicella, M. ; Ceci, L.R. ; America, T. ; Gallarani, R. ; Bode, W. ; Jongsma, M.A. ; Beekwilder, J. - \ 2003
European Journal of Biochemistry 270 (2003). - ISSN 0014-2956 - p. 10 - 19.
partial-purification - protease inhibitors - phage display - manduca-sexta - resistance - insects - plants - larvae - midgut - expression
Pest insects such as Helicoverpa spp. frequently feed on plants expressing protease inhibitors. Apparently, their digestive system can adapt to the presence of protease inhibitors. To study this, a trypsin enzyme was purified from the gut of insects that were raised on an inhibitor-containing diet. The amino-acid sequence of this enzyme was analysed by tandem MS, which allowed assignment of 66 f the mature protein amino acid sequence. This trypsin, called HzTrypsin-S, corresponded to a known cDNA sequence from Helicoverpa. The amino acid sequence is closely related (76 dentical) to that of a trypsin, HzTrypsin-C, which was purified and identified in a similar way from insects raised on a diet without additional inhibitor. The digestive properties of HzTrypsin-S and HzTrypsin-C were compared. Both trypsins appeared to be equally efficient in degrading protein. Four typical plant inhibitors were tested in enzymatic measurements. HzTrypsin-S could not be inhibited by > 1000-fold molar excess of any of these. The same inhibitors inhibited HzTrypsin-C with apparent equilibrium dissociation constants ranging from 1 nm to 30 nm. Thus, HzTrypsin-S seems to allow the insect to overcome different defensive proteinase inhibitors in plants.