Entomologia Experimentalis et Applicata
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Phenoloxidase: a key component of the insect immune systemAbstract The innate immune system in insects is composed of a large variety of specific and non‐specific responses that are activated in response to the presence of foreign agents. One important element in such responses is the enzyme phenoloxidase (PO). Here, we review recent progress in PO research and discuss new applications in the emerging field of ecological immunology. Phenoloxidase produces indole groups, which are subsequently polymerized to melanin. The enzymatic reactions in turn produce a set of intermediate products such as quinones, diphenols, superoxide, hydrogen peroxide, and reactive nitrogen intermediates, which are important during defense against bacterial (gram+ and −), fungal, and viral agents. Phenoloxidase requires a complex system of activation and inhibition that involves various cell types, PO zymogens, inhibitor enzymes, and signaling molecules. Finally, research in evolutionary ecology has studied the costs of PO in terms of resource use and pleiotropic relations with other key traits and functions. These studies indicate that PO is a costly trait, whose production and maintenance have fitness costs for hosts. Phenoloxidase does not seem to be an indicator of resistance but rather of host condition. Finally, we put forward some basic directions for future investigation of PO aimed at explaining its activating system, its substrates, its coordination with other immune components to fight off pathogens, and variation in PO in relation to gender, life stages, seasonality, and across different host species.
Entomologia Experimentalis et Applicata - Tập 142 Số 1 - Trang 1-16 - 2012
THE MECHANISM OF MALATHION‐RESISTANCE IN THE BLOWFLY CHRYSOMYA PUTORIAZUSAMMENFASSUNG DER MECHANISMUS DER MALATHION‐RESISTENZ BEI DER SCHMEISSFLIEGE CHRYSOMYA PUTORIA 1. Der zu dieser Untersuchung benutzte resistente Stamm von Chrysomya putoria stammt aus dem Kongo, wurde aber vorher etwa 6 Jahre lang im Labor gezüchtet. Frühere Untersuchungen ergaben, daß (1.) seine Resistenz hochspezifisch gegen Malathion und Malaoxon gerichtet ist, (2.) diese Resistenz durch nichtgiftige, dreifach substituierte Phosphor‐Verbindungen überwunden werden kann, die als Malathion‐Synergisten wirken, und (3.) diese Resistenz durch ein einzelnes, dominantes autosomales Gen vererbt wird. 2. Wenn der Stamm zu Homozygotie selektiert wurde, war er beträchtlich weniger fruchtbar als ein empfindlicher Schmeißfliegen‐Stamm. Vergleichende Messung der Lebensdauer, Eiproduktion, Schlüpf‐, Verpuppungs‐ und Puppenschlupfraten zeigte, daß der einzig deutliche Unterschied darin bestand, daß die Anzahl der täglich pro Weibchen produzierten Eier bei dem resistenten Stamm nur etwa halb so groß war wie die des anfälligen. 3. Durch Vergleich der entsprechenden LD 50‐Werte der beiden Stämme wurde ein Resistenzspektrum für Malathion‐Analoge erhalten und mit ähnlichen Spektren für Stubenfliegen und Mücken verglichen. Wie bei anderen Insekten wurde festgestellt, daß für die Resistenz die Alkyloxy‐Gruppe im Malathion‐Molekül entscheidend ist (höchste Resistenz mit Methoxy). Die Natur des Carboxy‐Alkyl‐Restes war relativ unwichtig. 4. Die Kutikula‐Durchdringungsrate des Malathion war in den beiden Stämmen etwa die gleiche. 5. Der Malathion‐Abbau durch den larvalen Fettkörper in vitro wurde gaschromatogra‐phisch gemessen und im resistenten Stamm größer befunden. Dieses Verfahren war jedoch nicht ideal und alle weiteren Versuche wurden daher mit 14 C‐markiertem Malathion durchgeführt. 6. Abbauprodukte des Malathion, die von larvalem Fettgewebe in vitro entstanden, wurden durch Dünnschichtchromatographie getrennt. Die einzige festgestellte Verbindung entsprach dem Rf‐Wert von Malathion‐Monoacid. Die Anreicherung desselben entsprach dem Verlust an Malathion und war bei dem resistenten Stamm durchgehend größer. 7. Die symmetrischen, dreifach substituierten Phosphor‐Verbindungen, welche sich in früheren Untersuchungen vorzugsweise in resistenten Stämmen als Synergisten von Malathion erwiesen hatten, wurden auf ihre Wirkung beim in vitro ‐Abbau von Malathion geprüft. Der Abbau wurde in beiden Stämmen bis auf einen Rest verhindert, der geringer war als der des nichtverhinderten empfindlichen Stammes. Andere Synergisten wurden ebenfalls, aber mit unterschiedlichen Ergebnissen erprobt; jedoch war keiner ebenso wirksam wie die der ursprünglichen Serien, die für Carboxyesterase‐Hemmer gehalten werden. 8. Larvale Fettkörper wurden homogenisiert und durch Zentrifugieren in verschiedene Fraktionen getrennt. Maximaler Malathion‐Abbau war nachweislich mit der Mikrosomen‐Fraktion verbunden. 9. Eindringen und Abbau des Malathion wurden in vivo an erwachsenen Schmeißfliegen untersucht. Das Eindringen verlief beim resistenten Stamm etwas schneller, während dann im Inneren Malathion‐Monoacid immer doppelt so hoch war wie Malathion. Das Umgekehrte galt für den empfindlichen Stamm. 10. Gewebe adulter Schmeißfliegen wurden homogenisiert und zentrifugiert (wie die larvalen Fettkörper) und wieder fand sich die maximale Aktivität in der Mikrosomen‐Fraktion. 11. Die Eigenschaften der Esterasen beider Stämme wurden untersucht. Die Cholinesterase‐Niveaus waren etwa gleich, aber die Ali‐Esterase‐Aktivität betrug in dem resistenten Stamm nur 10–20% der im empfindlichen gefundenen. 12. Homogenisierung und Zentrifugierung der Gewebe zeigten, daß die Ali‐Esterase‐Aktivität in der Mikrosomen‐Fraktion lokalisiert ist. 13. Beide Stämme wurden gekreuzt. Die auf Resistenz ausgelesene Hybridnachkommenschaft hatte niedrigere Ali‐Esterase‐Spiegel. Paarungen innerhalb eines auf niedrigen Ali‐Esterase‐Gehalt ausgelesenen Hybridstammes ergaben eine hochresistente Nachkommenschaft.
Entomologia Experimentalis et Applicata - Tập 12 Số 3 - Trang 243-267 - 1969
RELATION BETWEEN ELECTROPHORETIC ESTERASE PATTERNS AND ORGANOPHOSPHATE RESISTANCE IN MUSCA DOMESTICAAn Italian OP‐resistant strain C turned out to be heterogeneous for a gene on the 5th chromosome causing a difference in the mobility of an esterase in electrophoresis. Individuals containing only band 1 or 2 are homozygous for either allele, individuals containing esterase 1 and 2 are heterozygous. Two substrains were derived, E1 and E2 , homozygous for the allele for 1 and 2 respectively. These strains were found to be remarkably different in OP‐resistance. E1 is approximately equally resistant as strain C, and contains the breakdown enzyme degrading paraoxon and diazoxon. E2 has a lower resistance and does not contain the breakdown enzyme. The presence of the breakdown enzyme and the 1 esterase are controlled by the same gene allele, but they are certainly not identical. For instance the 1 band is quite stable, and is in solution in normal homogenates, whereas the breakdown enzyme is very labile and particulate. Therefore one allele, a C1 , controls both band 1 and the breakdown enzyme, the other, a C2 , seems to control only band 2. A similar situation was found in a susceptible strain, bwb; ocra , which had previously been shown to be heterogeneous for the ali‐esterase a . Two alleles of the a gene are present here: the a + allele controls the presence of band 1 and ali‐esterase a ; the a 2 allele seems to control band 2 only. The electrophoretic speed of the breakdown enzyme was found to be approximately equal to that of esterase 2. Zusammenfassung BEZIEHUNGEN ZWISCHEN ELEKTROPHORETISCHEM VERHALTEN VON ESTERASEN UND DER RESISTENZ VON STUBENFLIEGEN GEGEN ORGANISCHE PHOSPHORVERBINDUNGEN (OP) Ein italienischer OP‐resistenter Musca domestica ‐Stamm erwies sich als heterogen für ein Gen im 5. Chromosom, das einen Unterschied in der Beweglichkeit einer Esterase bei der Elektrophorese bedingt. Individuen, die nur die Bande 1 oder 2 enthalten, sind homozygot für jeweils das eine der beiden Allele. Individuen, welche die Esterase 1 und 2 enthalten, sind heterozygot. Es wurden zwei Unterstämme E1 und E2 abgezweigt, die jeweils für das Allel 1 und 2 homozygot sind. Diese Stämme erwiesen sich als bemerkenswert verschieden hinsichtlich der OP‐Resistenz. E1 ist annähernd so resistent wie Stamm C und enthält das Abbau‐Enzym, welches Paraoxon und Diazoxon zerstört. E2 hat eine geringere Resistenz und enthält kein Abbau‐Enzym. Die Gegenwart des Abbau‐Enzyms und der 1‐Esterase werden von dem gleichen Genallel kontrolliert, sind aber sicher nicht identisch. Z.B. ist Bande 1 ganz stabil und in normalen Homogenisaten in Lösung, während das Abbau‐Enzym sehr labil und ungelöst ist. Deshalb kontrolliert das eine Allel, a C1 , sowohl Bande 1 und das Abbau‐Enzym, das andere, a C2 , anscheinend nur Bande 2. Eine ähnliche Situation wurde in dem anfälligen Stamm, bwb; ocra , gefunden, der sich bereits früher als heterozygot für die Ali‐Esterase a erwiesen hatte. Dabei sind 2 Allele des a ‐Gens vorhanden: das a + ‐Allel kontrolliert die Anwesenheit von Bande 1 und Ali‐Esterase a ; das a 2 ‐Allel scheint nur Bande 2 zu kontrollieren. Die Elektrophorese‐Geschwindigkeit des Abbau‐Enzyms erwies sich als annähernd so groß wie die der Esterase 2.
Entomologia Experimentalis et Applicata - Tập 8 Số 3 - Trang 163-174 - 1965
THE DETOXICATION ENZYMES CAUSING ORGANOPHOSPHATE RESISTANCE IN THE HOUSEFLY; PROPERTIES, INHIBITION, AND THE ACTION OF INHIBITORS AS SYNERGISTSA comparison of the breakdown enzymes in OP‐resistant houseflies and the ali‐esterase of susceptible flies shows differences as well as similarities. In general both are rapidly phosphorylated by the OP‐compounds, but only in the case of the breakdown enzymes dephosphorylation can take place. The rate of phosphorylation of the breakdown enzymes by the toxicants is sometimes higher, sometimes lower than that of the ali‐esterase with the same compound. Studies of the breakdown reaction showed the Km to be in the order of 10−6 –10−8 M, the turnover numbers to range from 0.05–0.7 per minute. Whether dephosphorylation takes place depends on the type of breakdown enzyme and the nature of the phosphoryl group. For instance, in the malathion‐resistant strains only the dimethyl phosphorylated enzymes are dephosphorylated, but the dimethyl and dipropyl phosphorylated enzymes are not. Dephosphorylation of the enzymes of diazinon‐resistant strains occurs with both dimethyl and diethyl, but not with dipropyl compounds. Consequently hydrolysis of some OP‐compounds can be blocked by the addition of others that irreversibly phosphorylate the enzymes. Substances that can block the reaction have a marked synergistic action when sublethal doses are applied simultaneously with the OP‐compound to which a strain is resistant. There is evidence that the breakdown enzymes can still hydrolyse methyl butyrate and some other esters although at a rate which is only a few percents of that of the ali‐esterase. The problem as to how enzymes with a rather low breakdown capacity could confer high resistance is discussed. ZUSAMMENFASSUNG ABBAUENZYME ALS URSACHE DER PHOSPHORSÄURE ESTER‐RESISTENZ BEI DER STUBENFLIEGE; EIGENSCHAFTEN, HEMMUNG UND DIE SYNERGISTISCHE WIRKUNG VON HEMMENDEN SUBSTANZEN In phosphorsäureester‐resistenten Stubenfliegen sind Abbaufermente vorhanden, die die Fähigkeit zur Hydrolyse von Sauerstoffderivaten derjenigen Verbindungen besitzen, gegen die Resistenz aufgetreten ist. Diese Enzyme entstehen an Stelle einer in anfälligen Fliegen vorkommenden Ali‐Esterase. Das Auftreten der Ali‐Esterase und der Abbaufermente unterliegt dem Einfluß verschiedener Allele eines Gens. Durch eine Kombination biochemischer, genetischer und toxikologischer Arbeitsmethoden wurden Bedeutung und Eigenschaften dieser Enzyme untersucht. Die Hemmung der Ali‐Esterase durch organische Phosphorverbindungen wird durch eine irreversible Reaktion hervorgerufen, bei der eine Dialkylphosphorylierung des Enzyms stattfindet. Die modifizierten Ali‐Esterasen oder Abbaufermente unterscheiden sich von der Ali‐Esterase dadurch, daß der Reaktion mit den Produkten, gegen die Resistenz besteht, eine langsam fortschreitende Dephosphorylierung folgt. Diese Fähigkeit zur Hydrolyse bestimmter Verbindungen muß die Selektion der Allele hervorgerufen haben, die für die Bildung dieser Enzyme verantwortlich sind. Darüber hinaus wurden aber noch andere Veränderungen herbeigeführt: ein Verlust der Ali‐Esterase‐Aktivität, eine Änderung in der Affinität einer Anzahl Phosphorverbindungen gegenüber und eine Verminderung der Stabilität. Vier verschiedene Abbaufermente sind in verschiedenen resistenten Stämmen vorhanden. Zwei von ihnen können Diäthylverbindungen mit einer Umsatzzahl von 0.05 und 0.25 pro Minute hydrolysieren. Das Enzym mit der höheren Umsatzzahl spaltet auch Dimethyl‐Derivate; die Affinität für diese Verbindungen erscheint aber zur Ausbildung eines hohen Resistenzgrades zu niedrig. Zwei andere Fermente finden sich in Malathion‐resistenten Stämmen, von denen eines wegen seiner wahrscheinlichen Instabilität in vitro nicht untersucht werden konnte. Das andere Enzym spaltet Malaoxon und einige weitere Methylverbindungen, wobei die Affinität Malaoxon gegenüber höher ist, was möglicherweise die Ursache der ziemlich hohen Spezifizität bildet. Obwohl die Umsatzzahlen sehr niedrig sind und die Enzyme wohl nur einen geringen Teil des in vivo applizierten Giftes zu hydrolysieren vermögen, gestattet aber anscheinend ihre hohe Affinität für Phosphorverbindungen die für die Cholinesterasehemmung notwendige Inhibitormenge zu reduzieren und verursacht so die Resistenz. Die Abbaufermente können bestimmte Typen von Phosphorsäureestern hydrolysieren; sie werden aber noch durch andere Verbindungen dieser Stoffklasse irreversibel gehemmt. Solche Präparate sind zur Blockierung der in vitro stattfindenden Hydrolyse befàhigt und besitzen einen stark synergistischen Effekt, wenn sie mit den Thioverbindungen, gegen die Resistenz besteht, gleichzeitig appliziert werden. So werden die Abbaufermente der Malathion‐ und Parathion‐resistenten Stämme durch Propylparaoxon irreversibel phosphoryliert. Sublethal Mengen dieser Substanz reduzieren die Resistenz beträchtlich.
Entomologia Experimentalis et Applicata - Tập 4 Số 4 - Trang 311-333 - 1961
Further comments on analysis of covariance in insect dietary studiesAbstract Raubenheimer & Simpson (1992) recently discussed the advantages of using analysis of covariance in insect dietary studies as an alternative to the more conventional ratio‐based nutritional indices. We expand on some interpretations of Raubenheimer & Simpson and illustrate our points with examples from published and unpublished data sets. Specifically, we show that an ANCOVA on biomass gain incorporating initial biomass as a covariate provides information not immediately available using the analysis suggested by Raubenheimer & Simpson (ANCOVA on final biomass incorporating initial biomass as a covariate). Second, we show that dietary studies in which the covariate (food consumption) is affected by diet can provide information about the relative importance of preingestive effects (e.g., deterrence) and postingestive effects (e.g., antibiosis) on performance. Cautions about this latter use of ANCOVA are discussed.
Entomologia Experimentalis et Applicata - Tập 69 Số 3 - Trang 263-275 - 1993
Analysis of covariance: an alternative to nutritional indicesAbstract Some statistical problems are added to the growing list of cautionary tales regarding the use of the conventional, ratio‐based nutritional indices (RCR, RGR, ECI, AD and ECD). Analysis of ratios is based on the, probably unrealistic, assumption of an isometric relationship between denominator and numerator variables. Analysis of covariance (ANCOVA) makes less restrictive assumptions, and additionally provides important information about the data which is lost by using ratio variables. We demonstrate, using computer‐generated data sets, some of the pitfalls of statistical analysis of ratios and illustrate how these may be avoided using ANCOVA. Some possible consequences of such statistical iniquities for biological interpretations are discussed.
Entomologia Experimentalis et Applicata - Tập 62 Số 3 - Trang 221-231 - 1992
Methyl jasmonate‐induced nicotine production in Nicotiana attenuata: inducing defenses in the field without woundingAbstract The functional significance of herbivore‐induced plant traits known to directly or indirectly influence herbivore performance remains largely untested under field conditions due to the difficulty of uncoupling the response to herbivory from the act of herbivory. The signals that activate many of the induced responses in plants are endogenously produced in response to wounding, unlike many of the predator‐induced responses found in aquatic invertebrates (which are activated by exogenous cues derived from predators). Jasmonates, endogenously‐produced damage signals, activate diverse wound‐induced responses in plants including induced nicotine production in Nicotiana sylvestris. The results presented here are from two experiments which illustrate the use of jasmonates to uncouple induced nicotine production in Nicotiana attenuata (Torrey ex. Watson) from wounding. The exogenous addition of methyl jasmonate (MJ) in small quantities (11 μg for a 1.4 g dry mass plant) to roots of hydroponically‐grown plants induces de novo nicotine synthesis and increases whole‐plant nicotine concentrations just as wounding does. The MJ‐induced changes were proportional to the quantity of MJ given. Moreover, the effects of MJ were additive to the effects of damage. Applications of MJ to shoots were less effective. Root treatments also worked with plants growing in a field plot. The application of MJ represents a promising tool for examining the functional significance of induced nicotine responses in plants growing in their native environments.
Entomologia Experimentalis et Applicata - Tập 80 Số 1 - Trang 213-220 - 1996
Multitrophic effects of herbivore‐induced plant volatiles in an evolutionary contextAbstract Herbivorous and carnivorous arthropods use plant volatiles when foraging for food. In response to herbivory, plants emit a blend that may be quantitatively and qualitatively different from the blend emitted when intact. This induced volatile blend alters the interactions of the plant with its environment. We review recent developments regarding the induction mechanism as well as the ecological consequences in a multitrophic and evolutionary context. It has been well established that carnivores (predators and parasitoids) are attracted by the volatiles induced by their herbivorous victims. This concerns an active plant response. In the case of attraction of predators, this is likely to result in a fitness benefit to the plant, because through consumption a predator removes the herbivores from the plant. However, the benefit to the plant is less clear when parasitoids are attracted, because parasitisation does usually not result in an instantaneous or in a complete termination of consumption by the herbivore. Recently, empirical evidence has been obtained that shows that the plant's response can increase plant fitness, in terms of seed production, due to a reduced consumption rate of parasitized herbivores. However, apart from a benefit from attracting carnivores, the induced volatiles can have a serious cost because there is an increasing number of studies that show that herbivores can be attracted. However, this does not necessarily result in settlement of the herbivores on the emitting plant. The presence of cues from herbivores and/or carnivores that indicate that the plant is a competitor‐ and/or enemy‐dense space, may lead to an avoidance response. Thus, the benefit of emission of induced volatiles is likely to depend on the prevailing faunal composition. Whether plants can adjust their response and influence the emission of the induced volatiles, taking the prevalent environmental conditions into account, is an interesting question that needs to be addressed. The induced volatiles may also affect interactions of the emitting plant with its neighbours, e.g., through altered competitive ability or by the neighbour exploiting the emitted information. Major questions to be addressed in this research field comprise mechanistic aspects, such as the identification of the minimally effective blend of volatiles that explains the attraction of carnivores to herbivore‐infested plants, and evolutionary aspects such as the fitness consequences of induced volatiles. The elucidation of mechanistic aspects is important for addressing ecological and evolutionary questions. For instance, an important tool to address ecological and evolutionary aspects would be to have plant pairs that differ in only a single trait. Such plants are likely to become available in the near future as a result of mechanistic studies on signal‐transduction pathways and an increased interest in molecular genetics.
Entomologia Experimentalis et Applicata - Tập 97 Số 3 - Trang 237-249 - 2000
Absence of odour‐mediated avoidance of heterospecific competitors by the predatory mite Phytoseiulus persimilisAbstract Arthropods use odours associated with the presence of their food, enemies and competitors when searching for patches. Responses to these odours therefore determine the spatial distribution of animals, and are decisive for the occurrence and strength of interactions among species. Therefore, a logical first step in studying food web interactions is the analysis of behaviour of individuals that are searching for patches of food. We followed this approach when studying interactions in an artificial food web occurring on greenhouse cucumber in the Netherlands. In an earlier paper we found that one of the predators of the food web, the predatory mite Phytoseiulus persimilis Athias‐Henriot, used to control spider mites, discriminates between odours from plants with spider mites, Tetranychus urticae Koch, and plants with spider mites plus conspecific predators. The odours used for discrimination are produced by adult prey in response to the presence of predators, and probably serve as an alarm pheromone to warn related spider mites. Other predator species may also trigger production of this alarm pheromone, which P. persimilis could use in turn to avoid plants with heterospecific predators. We therefore studied the response of the latter to odours from plants with spider mites and 3 other predator species, i.e. the generalist predatory bug Orius laevigatus (Fieber), the polyphagous thrips Frankliniella occidentalis and the spider‐mite predator Neoseiulus californicus (McGregor). Both olfactometer and greenhouse release experiments yielded no evidence that P. persimilis avoids plants with any of the 3 heterospecific predators. This suggests that these predators do not elicit production of alarm pheromones in spider mites, and we argue that this is caused by a lack of coevolutionary history. The consequences of the lack of avoidance of heterospecific predators for interactions in food webs and biological control are discussed.
Entomologia Experimentalis et Applicata - Tập 92 Số 1 - Trang 73-82 - 1999
Test for predation effects of single versus multiple species of generalist predators: spiders and their insect preyAbstract The prediction that single spider species (as exemplary generalist predators) limit associated prey populations to the same extent that species assemblages do was tested in a well controlled and replicated old field experiment involving the following treatments: (1) the natural spider assemblage (2) a numerically prominent web building spider, (3) a numerically prominent wandering spider, (4) a biomass prominent web‐builder, and (5) a biomass prominent wandering spider. Pest insect numbers were significantly higher in spider removal controls than in any spider treament over the four month period of the study, both in terms of total numbers and per spider effects. The individual spider species, in general, showed reduced prey limitation effects relative to that of the spider assemblage, though the magnitudes of these differences were small when compared to those exhibited between the various treatments and the spider removal control. When insect numbers were partitioned according to taxa, no treatment was found to have limited the predaceous insects nor the phytophagous hemipterans. All treatments, however, showed significant limiting effects on the phytophagous homopterans, coleopterans, and dipterans in the old field system, and other taxa were significantly reduced in at least one treatment in addition to the spider assemblage as a whole.
Entomologia Experimentalis et Applicata - Tập 84 Số 2 - Trang 147-155 - 1997
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