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Time course of cooxidation between chlorogenic acid (CHA) and rutin, catalyzed by tomato PPO, assayed separately or in mixture. The percent of the substrate that was oxidized at each time point was calculated by subtracting the initial amount of substrate (20 nmol) minus the amount that remained at the end of the reaction time. Aliquots of 1-ml of each reaction mixture were stopped and processed at each time point. A constant volume from each treatment was chromatographed on TLC plates at each time point and developed in 2% formic acid. The amount of unoxidized substrate remaining was semiquantified by comparison to known standards chromatographed under the same conditions. Values shown are the mean of three replicates. Rf: CHA, 0.46; rutin, 0.24.
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The susceptibility of noctuid larvae to baculoviral infection is markedly affected by phytochemicals ingested during the acquisition of viral inoculum on foliage. We hypothesized that a major process causing phytochemical inhibition of viral disease is phenolic oxidation by phenolases, particularly peroxidase (POD), which subsequently generates fre...
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... The early onset of apoptosis in infected insect cells can dramatically reduce virus concentrations, with reductions up to 50 fold 37,38 . Oxidative stress in the midgut of lepidopterans due to plant-mediated peroxidase activity has been shown to reduce baculovirus activity and insect death 39 . The rapid sloughing of infected midgut epithelial cells before the establishment of a systemic infection reduces viral susceptibility, and reactive oxygen species may promote sloughing by damaging midgut cells 40 . ...
Four crop plants known to be hosts for the lepidopteran Trichoplusia ni (soybean, green bean, cotton, and cabbage) were treated with the biopesticide AfMNPV baculovirus in a dosage response assay. Treated soybean had, on average, a 6-fold increase in virus activity compared with the other crops. Leaf trichomes on soybeans were not found to be responsible for the observed increase of insecticidal activity. Three flavonoid compounds (daidzein, genistein, and kaempferol) were uniquely found only in the soybean crop, and were not detected in cotton, cabbage, or green bean plant matter. The individual flavonoid compounds did not cause T ni. mortality in no-virus assays when incorporated into artificial insect diet. The combination of the three flavonoid compounds at leaf level concentrations significantly increased baculovirus activity in diet incorporation assays. When the daidzein, genistein, and kaempferol were added to artificial diet, at 3.5–6.5 × leaf level concentrations, virus activity increased 1.5, 2.3, and 4.2-fold for each respective flavonoid. The soybean flavonoid compounds were found to synergistically improve baculovirus activity against T. ni.
... Insects inoculated with AcMNPV (Autographa californica MNPV) on cotton were less susceptible and this was positively correlated with levels of foliar peroxidase. Previous studies suggested that reactive oxygen species associated with peroxidase activity damage the lining of the midgut and cells are sloughed off at early infection (Hoover et al., 1998c). By administering an optical brightener (thought to enhance the retention of gut cells) the effect of feeding on cotton was reversed (Hoover et al., 2000). ...
The susceptibility of Spodoptera litura to SlMNPV infection was markedly affected by phyto-chemicals ingested during the acquisition of viral inoculum on foliage of tomato and cauliflower. The LD50 values computed for second, third and fourth instar larvae assayed on tomato leaves were 254, 819 and 23395 PIBs/larva, respectively whereas, it was 326, 1719 and 43843 PIBs/larva for respective instars when assayed on cauliflower leaves. Thus LD50 values for second, third and fourth instar larvae were 1.28-, 2.09- and 1.87- fold lower, respectively in tomato leaves. Similarly, LT50 values for second, third and fourth instar larvae assayed on tomato leaves were 7.1 and 7.5 days, respectively at inoculum dose of 2.7×104 PIBs/larva whereas, it was 7.7 and 8.0 days for respective instars when assayed on cauliflower leaves at same inoculum. This result also showed that the S. litura were more susceptible on tomato leaves in comparison to cauliflower leaves as the time required for mortality was lower in tomato leaves. The possible biochemical bases for differential level of mortality of S. litura larvae on tomato and cauliflower crops needs to be investigated.
... Thus, pH is a feasible control variable affecting the conversion of antioxidant to ES "catalysts" in bioenergy applications. As revealed by the Nernst equation, the pH-dependent reduction potentials of some polyphenolic compounds (e.g., caffeic acid, catechin, and chlorogenic acid) are slightly decreased as the pH increases from 7.0 to 10.0 [140]. Moreover, as observed in their CV profiles, the E pa and E pc values of catechin, chlorogenic acid, epicatechin, epigallocatechin gallate, and gallic acid can shift toward lower values as the pH increases from 5.0 to 6.0 [141] according to Le Chatelier's principle and the Nernst equation. ...
Abstract For renewable and sustainable bioenergy utilization with cost-effectiveness, electron-shuttles (ESs) (or redox mediators (RMs)) act as electrochemical “catalysts” to enhance rates of redox reactions, catalytically accelerating electron transport efficiency for abiotic and biotic electrochemical reactions. ESs are popularly used in cellular respiratory systems, metabolisms in organisms, and widely applied to support global lives. Apparently, they are applicable to increase power-generating capabilities for energy utilization and/or fuel storage (i.e., dye-sensitized solar cell, batteries, and microbial fuel cells (MFCs)). This first-attempt review specifically deciphers the chemical structure association with characteristics of ESs, and discloses redox-mediating potentials of polyphenolics-abundant ESs via MFC modules. Moreover, to effectively convert electron-shuttling capabilities from non-sustainable antioxidant activities, environmental conditions to induce electrochemical mediation apparently play critical roles of great significance for bioenergy stimulation. For example, pH levels would significantly affect electrochemical potentials to be exhibited (e.g., alkaline pHs are electrochemically favorable for expression of such electron-shuttling characteristics). Regarding chemical structure effect, chemicals with ortho- and para-dihydroxyl substituents-bearing aromatics own convertible characteristics of non-renewable antioxidants and electrochemically catalytic ESs; however, ES capabilities of meta-dihydroxyl substituents can be evidently repressed due to lack of resonance effect in the structure for intermediate radical(s) during redox reaction. Moreover, this review provides conclusive remarks to elucidate the promising feasibility to identify whether such characteristics are non-renewable antioxidants or reversible ESs from natural polyphenols via cyclic voltammetry and MFC evaluation. Evidently, considering sustainable development, such electrochemically convertible polyphenolic species in plant extracts can be reversibly expressed for bioenergy-stimulating capabilities in MFCs under electrochemically favorable conditions.
... Both these entomopathogens can be altered by the phytochemistry of plants and such tritrophic interactions have been observed on a wide variety of plants and insect herbivores (Keating & Yendol, 1987;Keating et al., 1990a;Forschler et al., 1992;Appel & Schultz, 1994;Hwang et al., 1995;Farrar & Ridgway, 2000;Beveridge & Elek, 2001;Kouassi et al., 2001;reviewed in Cory & Hoover, 2006) including tree-feeding Lepidoptera (Farrar et al., 1996;Kouassi et al., 2001). Phytochemical properties such as foliar pH, concentrations of tannins and other phenolics (e.g., Lüthy et al., 1985;Keating, et al., 1990a;Ludlum et al., 1991;Appel & Schultz, 1994;Hwang et al., 1995;Hoover et al., 1998a), serine protease inhibitors (MacIntosh et al., 1990), oxidizing enzymes (Ludlum et al., 1991;Appel & Schultz, 1994;Hoover et al., 1998a;Hoover et al., 1998b), and allelochemicals (Felton & Dahlman, 1984;Krischik et al., 1988) have been linked to altered susceptibility of insects to entomopathogens. ...
... Both these entomopathogens can be altered by the phytochemistry of plants and such tritrophic interactions have been observed on a wide variety of plants and insect herbivores (Keating & Yendol, 1987;Keating et al., 1990a;Forschler et al., 1992;Appel & Schultz, 1994;Hwang et al., 1995;Farrar & Ridgway, 2000;Beveridge & Elek, 2001;Kouassi et al., 2001;reviewed in Cory & Hoover, 2006) including tree-feeding Lepidoptera (Farrar et al., 1996;Kouassi et al., 2001). Phytochemical properties such as foliar pH, concentrations of tannins and other phenolics (e.g., Lüthy et al., 1985;Keating, et al., 1990a;Ludlum et al., 1991;Appel & Schultz, 1994;Hwang et al., 1995;Hoover et al., 1998a), serine protease inhibitors (MacIntosh et al., 1990), oxidizing enzymes (Ludlum et al., 1991;Appel & Schultz, 1994;Hoover et al., 1998a;Hoover et al., 1998b), and allelochemicals (Felton & Dahlman, 1984;Krischik et al., 1988) have been linked to altered susceptibility of insects to entomopathogens. ...
... Efficacies of Btk and LdMNPV were strongly affected by chestnut genotype in agreement with several other studies that have found host plant dependent variation in performance of these entomopathogens (Keating & Yendol, 1987;Keating et al., 1990a;Hwang et al., 1995;Kouassi et al., 2001). Without an analysis of the foliar chemistry among chestnut genotypes, the mechanism(s) underlying the differential pathogenicity of these entomopathogens is largely speculative, but mechanisms in other systems have involved leaf pH (Ignoffo & Garcia, 1966;Keating et al., 1990b), oxidizing enzymes (Felton & Duffey, 1990;Hwang et al., 1995;Hoover et al., 1998a), and phenolics such as tannins (Keating et al., 1988(Keating et al., , 1989(Keating et al., , 1990aHwang et al., 1995). ...
American chestnut (Castanea dentata [Marsh.] Borkh.) was once the dominant hardwood species in Eastern North America before an exotic fungal pathogen, Cryphonectria parasitica (Murrill) Barr, functionally eliminated it across its range. One promising approach toward restoring American chestnut to natural forests is development of blight‐tolerant trees using genetic transformation. However, transformation and related processes can result in unexpected and unintended phenotypic changes, potentially altering ecological interactions. To assess unintended tritrophic impacts of transgenic American chestnut on plant–herbivore interactions, gypsy moth (Lymantria dispar L.) caterpillars were fed leaf disks excised from two transgenic events, Darling 54 and Darling 58, and four control American chestnut lines. Leaf disks were previously treated with an LD50 dose of either the species‐specific Lymantria dispar multiple nucleopolyhedrovirus (LdMNPV) or the generalist pathogen Bacillus thuringiensis subsp. kurstaki (Btk). Mortality was quantified and compared to water blank controls. Tree genotype had a strong effect on the efficacies of both pathogens. Larval mortality from Btk‐treated foliage from only one transgenic event, Darling 54, differed from its isogenic progenitor, Ellis 1, but was similar to an unrelated wild‐type American chestnut control. LdMNPV efficacy was unaffected by genetic transformation. Results suggest that although genetic modification of trees may affect interactions with other non‐target organisms, this may be due to insertion effects, and variation among different genotypes (whether transgenic or wildtype) imparts a greater change in response than transgene presence. This article is protected by copyright. All rights reserved
... These compounds affect insects directly, by altering feeding behavior, damaging midgut tissues, and interfering with digestive processes. These chemical compounds also affect insects indirectly by interacting with baculoviruses in the insect midgut (Hoover et al 1998). Soybeans produce these chemical defenses either constitutively or via induction due to herbivores feeding on the plant. ...
... The larvae were then removed from their diet and starved overnight. This ensured that all larvae were at the same development stage since larval age affects the susceptibility of the larvae to the virus (Hoover et al 1998). We chose to examine time to death using fourth instars since the fourth instars not only cause a great deal of defoliation but also play an important part in the disease transmission process (Elkinton and Liebhold 1990;Elderd and Reilly 2014). ...
The standard approach to modeling survival times, or more generally, time to event data, is often based on parametric assumptions that may not fit the data collected well. One of the goals of this article is to discuss and compare several commonly used parametric and non-parametric, as well as a Bayesian semi-parametric method for survival data. We do so in the context of the data from an experimental system where insect herbivores become infected when consuming a lethal virus along with the plant on which the virus resides. We used data collected on individual insects that were fed known doses of virus along with varying genotypes of a single plant species (soybean), to compare how the insect’s diet affects its time to death. Through hazard characterization and model selection, we found that the flexible semi-parametric analysis is better at describing the time-to-death data while maintaining a relatively parsimonious form. Unlike the standard parametric and non-parametric approaches, the Bayesian semi-parametric approach better captured the rapid decline in the hazard function after a window of time where the host was most vulnerable to the virus. For our study system, being able to accurately model time to death and quantify how plant genetics affects within-insect disease processes allows us to gain a better understanding of the host-pathogen interaction at an individual level. While we show the appropriateness of the Bayesian semi-parametric approach for infection data, this method readily applies to data sets concerned with characterizing a time until any event.
... Overall, these induced changes affect insects directly by altering feeding behavior, damaging midgut tissues, and interfering with digestive processes (Shikano 2017). These changes may also affect insects indirectly by interacting with baculoviruses in insect midguts (Hoover et al. 1998. ...
A plant's induction of secondary defenses helps to decrease herbivore damage by changing resource quality. While these chemical or physical defenses may directly decrease herbivory, they can also have indirect consequences. In a tritrophic system consisting of a plant, an insect herbivore, and an insect pathogen, plant based trait‐mediated indirect effects (TMIEs) can alter host–pathogen interactions and, thereby, indirectly affect disease transmission. In a series of field experiments, individual soybean plants (Glycine max) were sprayed with either a jasmonic acid (JA) solution to trigger induction of plant defenses or a similar control compound. Fall armyworm (Spodoptera frugiperda) larvae along with varying amounts of a lethal baculovirus were placed on the plants to measure transmission. Induction of plant defenses decreased viral transmission due to increased population heterogeneity arising from changes in individual susceptibility. The change in susceptibility via TMIEs was driven by a decrease in feeding rates and an increase viral dose needed to infect larvae. While the induction against herbivore attack may decrease herbivory, it can also decrease the efficacy of the herbivore's pathogen potentially to the plant's detriment. While TMIEs have been well‐recognized for being driven by top‐down forces, bottom‐up interactions can dictate community dynamics and, here, epizootic severity.
... Moreover, feeding by virus-infected fall armyworms on induced foliage significantly reduced the numbers of virus OBs produced compared to infected fall armyworms feeding on non-induced foliage (Shikano et al., 2017a), which is likely to influence levels of secondary cycling of virus. Lastly, mixing of virus OBs with induced phytochemicals in the midgut can significantly inhibit virus-induced mortality (Hoover et al., 1998a(Hoover et al., , 1998b(Hoover et al., , 1998cShikano et al., 2017b). Though not observed in the present study, this inhibitory effect of induced foliage on virus efficacy was evident when we previously allowed fall armyworms to ingest SfMNPV OBs on induced soybean leaf disks (Shikano et al., 2017b). ...
... It can prevent the apoptosis and sloughing of infected midgut cells (Dougherty et al., 2006;Hoover et al., 2000;Washburn et al., 1998) and prevent the formation of the peritrophic matrix by inhibiting chitin synthetase in vitro (Bartnicki-Garcia et al., 1994;Wang and Granados, 2000). M2R is also suggested to inhibit plant oxidative enzymes assayed in vitro (Hoover, unpublished data), such as peroxidases and polyphenol oxidases which can influence baculovirus efficacy (Felton and Duffey, 1990;Hoover et al., 1998aHoover et al., , 1998bHoover et al., , 1998cShikano et al., 2017b). In insect-baculovirus systems where the host has effective systemic resistance mechanisms, plant-mediated variation in the strength of insect cellular and humoral immune responses may have some influence on developmental resistance, especially since immunocompetence tends to increase with insect body weight (Vogelweith et al., 2013). ...
Plants damaged by herbivore feeding can induce defensive responses that reduce herbivore growth. The slow-growth, high-mortality hypothesis postulates that these non-lethal plant defenses prolong the herbivore's period of susceptibility to natural enemies, such as predators and parasitoids. While many juvenile animals increase their disease resistance as they grow, direct tests of the slow-growth, high-mortality hypothesis in the context of plant-herbivore-pathogen interactions are lacking. Caterpillars increase their resistance to lethal baculoviruses as they develop within and across instars, a phenomenon termed developmental resistance. Progression of developmental resistance can occur through age-related increases in systemic immune functioning and/or midgut-based resistance. Here, we examined the slow-growth, high-mortality hypothesis in the context of developmental resistance of caterpillars to baculoviruses. Intra-stadial (within-instar) developmental resistance of the fall armyworm, Spodoptera frugiperda, to an oral inoculum of the baculovirus SfMNPV increased more rapidly with age when larvae were fed on non-induced foliage than foliage that was induced by jasmonic acid (a phytohormone that up-regulates plant anti-herbivore defenses). The degree of developmental resistance observed was attributable to larval weight at the time of virus inoculation. Thus, slower growth on induced plants prolonged the window of larval susceptibility to the baculovirus. Developmental resistance on induced and non-induced plants was absent when budded virus was injected intrahemocoelically bypassing the midgut, suggesting that developmental resistance was gut-based. Addition of fluorescent brightener, which weakens midgut-based resistance mechanisms to oral virus challenge, abolished developmental resistance. These results highlight the impact of plant defenses on herbivore growth rate and consequences for disease risk.
... Among phytochemicals, foliar peroxidase (POD) is particularly important. The higher the POD activity, the more free radicals were generated in crushed foliage, and the more free radicals generated, the lower the incidence of viral disease (Hoover et al., 1998). For instance, larvae of Heliothis virescens fed on baculovirus-treated cotton leaves showed lower virus-induced mortality at higher POD levels in cotton leaves (Hoover et al., 2000). ...
It has been reported that the susceptibility of insect herbivores to entomoviruses is affected by phytochemicals ingested during the acquisition of viral inoculum on the foliage of host plants. However, the relationship between this susceptibility and phytochemicals is poorly understood. To test this hypothesis of plant‐mediated effects on this susceptibility, we measured the effects of foliage from three plants, soybeans (Glycine max), collards (Brassica oleracea) and water convolvuluses (Ipomoea aquatica), on the susceptibility of larval beet armyworm (Spodoptera exigua) to nucleopolyhedrovirus (NPV), and analysed six foliar chemicals (total phenolics, peroxidase [POD], catalase [CAT], superoxide dismutase [SOD], endochitinase and exochitinase) in the three plants, respectively. The results of exponential modelling indicated that the LD50s (median lethal dose) of NPV to larvae increased with the increase in both phenolics and POD but declined with the increase in four other foliar chemicals, while the opposite trend was found between median lethal time (LT50) of NPV and the six foliar chemicals. This study reveals that phenolics and POD decrease host susceptibility to the entomoviruses and that CAT, SOD, endochitinase and exochitinase increase this susceptibility.
... For instance, the balance may shift towards the pyroxydizers (tannins, phenols, etc.). Consequently, the decrease in mortality will be mediated through the mechanisms that can either directly damage the viral particles with the oxygen radicals or damage the infected midgut cells by the radicals, which can result in the gut autopurification from the infection (Hoover et al., 1998). If the balance is shifted towards the antioxidants (alfa-tocopherol, ascorbic acid, glutathione, etc.), the protection of viral substances against the radical damage upon feeding with such a plant may be observed; it can increase the efficiency of the virus. ...
The effect of a number of plant extracts on the susceptibility of experimental insects to enthomopathogenic microorganisms has been studied. It is shown that the weight of the wax moth Galleria mellonella larvae tends to decrease by 30–50% under the treatments of polar and nonpolar extracts from the ledum sprouts and the reindeer lichen, while the crude hemlock extract had the opposite effect, contributing to the larva weight gain by approximately 30%. The treatment with the reindeer lichen extract causes synergistic effects on mortality from both the nuclear polyhedrosis virus and the fungal infection in the gypsy moth Lymantria dispar and the wax moth, respectively. It has been determined that the main components of this extract are perlatolic acid, usnic acid, and a third component whose exact chemical identity is still unknown. The usnic acid is the most prospective additive component to entomopathogenic microorganisms. The treatment with the usnic acid caused the increase in mortality from the entomopathogenic fungi Metarhizium robertsii and Beauveria bassiana in the Colorado potato beetle Leptinotarsa decemlineata and the wax moth. However, the maximum effect occurs only after the treatment with the crude extract, which can be explained by either the combined effects of all the extract components or the change in a range of the properties of the components in the presence of the other crude extract components.
... The majority of OBs produced in infected phytophagous insects is likely to arrive at the soil surface having been washed by rainfall or by OB-contaminated leaves that senesce and fall from the plant onto the soil. Those OBs that have not been previously inactivated by exposure to ultraviolet solar radiation (Jones et al., 1993), or chemically inactivated by plant secondary chemicals (Hoover et al., 1998), are likely to persist in the soil for extended periods (Jaques, 1974;Thompson et al., 1981). ...
The soil is the most important reservoir of baculovirus occlusion bodies (OBs) in the environment. The ability of the earthworm Eisenia fetida to transport OBs of Spodoptera frugiperda multiple nucleopolyhedrovirus was examined in laboratory terraria filled with an artificial soil. OBs were detected in soil samples using a soil - diet incorporation bioassay, for which the 50% lethal concentration was estimated at 2.7 x 106 OBs/g soil in S. frugiperda second instars. Incubation of earthworms in soil containing 109 OBs for 7 days did not result in a significant loss of OB virulence compared to soil without earthworms. The earthworm intestine was found to be slightly acidic, with acid-base indicators applied to lengths of dissected intestine suggesting a pH of 6.0 – 6.3. Despite their epigean habits, E. fetida individuals were observed to form burrows up to 22.5 cm deep in laboratory terraria. Soil-diet bioassays indicated the presence of OBs at depths of 6-8, 14-16 and 22-24 cm in samples taken at 1, 7 and 14 days following the application of 109 OBs to the surface of terraria containing earthworms. In contrast, OBs were only detected in samples from the soil surface in terraria without earthworms. We conclude that earthworms likely affect the distribution and dynamics of OB populations in soil habitats.
