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Dynamics of mortality (a, c, e) and body weight (b, d, f) of the second, third and fourth instar Colorado potato beetle larvae after inoculation with B. bassiana (1 × 106 conidia ml-1) and treatment of foliage with FUA (0.03%). The control insects were inoculated with a water-Tween 20 solution (0.03%) and were allowed to eat potato leaves treated with a water-acetone (5%) solution. The vertical bars represent the standard errors. The asterisks (*) show the estimated synergistic effect (χ2 > 4.0; df = 1; P < 0.05; Table S1) as in Robertson and Preisler.46 The dagger (†) represents the significant effect of FUA on the weight of larvae (two-way ANOVA, F1.8 > 10.2; P < 0.02).
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Background:
The search for compounds that interact synergistically with entomopathogenic fungi is aimed at enhancing the efficacy and stability of biological products against pest insects e.g., against the Colorado potato beetle (CPB). We hypothesized that fluorine-containing derivatives of usnic acid (FUA) could be candidates for development of m...
Citations
... The (+)-UA enantiomer is prevalent in nature and is commercially available [5]. Chemical modification of UA results in highly active derivatives against mycobacteria [6], viruses [7,8], and insects [9]; practically all the derivatives are less generally toxic than their parent [10,11]. ...
Usnic acid (UA) is a secondary metabolite of lichens that exhibits a wide range of biological activities. Previously, we found that UA derivatives are effective inhibitors of tyrosyl-DNA phosphodiesterase 1 (TDP1). It can remove covalent complex DNA-topoisomerase 1 (TOP1) stabilized by the TOP1 inhibitor topotecan, neutralizing the effect of the drugs. TDP1 removes damage at the 3′ end of DNA caused by other anticancer agents. Thus, TDP1 is a promising therapeutic target for the development of drug combinations with topotecan, as well as other drugs for cancer treatment. Ten new UA enamino derivatives with variation in the terpene fragment and substituent of the UA backbone were synthesized and tested as TDP1 inhibitors. Four compounds, 11a-d, had IC50 values in the 0.23-0.40 μM range. Molecular modelling showed that 11a-d, with relatively short aliphatic chains, fit to the important binding domains. The intrinsic cytotoxicity of 11a-d was tested on two human cell lines. The compounds had low cytotoxicity with CC50 ≥ 60 μM for both cell lines. 11a and 11c had high inhibition efficacy and low cytotoxicity, and they enhanced topotecan's cyto-toxicity in cancerous HeLa cells but reduced it in the non-cancerous HEK293A cells. This "protec-tive" effect from topotecan on non-cancerous cells requires further investigation.
... The ability of Lasius fuliginosus milkers to detect and remove aphids covered with conidia was investigated according to Novgorodova and Kryukov [34]. One half of experimental aphids were treated with Beauveria bassiana (hereafter referred to as fungus or conidia-contaminated) using a standard method of dipping insect in a suspension of fungus [52,53], which was preliminary adapted for aphids. Each of these individuals was submerged for 2-3 s in the conidia suspension in distilled water (2 × 10 7 conidia ml −1 ). ...
The ability of ants to detect and remove conidia-contaminated aphids, aimed at limiting contacts with potentially dangerous entities, is an effective antifungal mechanism to prevent the spread of infection among both their nestmates and aphids, their main suppliers of carbohydrates. However, the spread and the scale of this quarantining behaviour among ants are still scarcely studied. Among seven ant species studied, active usage of quarantining behaviour was found only in Formica ants. The behaviour of Lasius fuliginosus (Latreille) aphid milkers towards Chaitophorus populeti (Panzer) aphids covered with conidia of Beauveria bassiana (Balsamo-Crivelli) Vuillemin was studied in the field. Most aggressive milkers quickly detected and removed conidia-contaminated aphids from the plant, carrying them down and placing them some distance away from the experimental aspen trees. In general, active usage of quarantining behaviour towards conidia-contaminated aphids was found to be not limited to the genus Formica, but typical of L. fuliginosus as well. The response of milkers of L. fuliginosus and Formica s. str. ants to living aphids covered with conidia is quite similar. Removal of most fungus-contaminated aphids from the plant enables these ants to reduce the risk of infection transmission among both their nestmates and aphids.
... It is well-known that these toxicants may significantly modulate the susceptibility of hosts to fungal pathogens 10,11 . Various approaches for integrated pest control have been developed on this basis [12][13][14][15][16][17][18] . Researchers usually explain synergy between pathogenic fungi and insecticides by altering the immune response to fungal infections, as well as developmental and behavioral disorders. ...
... The rapid development of resistance to various chemical insecticides requires the development of integrated approaches to the control of L. decemlineata populations 38 . One of these approaches may be employing a combination of insecticides and entomopathogens 13,17,39,40 . Previously, we studied the immunophysiological mechanisms of the synergy between the fungus Metarhizium robertsii and the macrocyclic lactones avermectins after a combined treatment to control the Colorado potato beetle 39,40 . ...
Fungal infections and toxicoses caused by insecticides may alter microbial communities and immune responses in the insect gut. We investigated the effects of Metarhizium robertsii fungus and avermectins on the midgut physiology of Colorado potato beetle larvae. We analyzed changes in the bacterial community, immunity-and stress-related gene expression, reactive oxygen species (ROS) production, and detoxification enzyme activity in response to topical infection with the M. robertsii fungus, oral administration of avermectins, and a combination of the two treatments. Avermectin treatment led to a reduction in microbiota diversity and an enhancement in the abundance of enterobacteria, and these changes were followed by the downregulation of Stat and Hsp90, upregulation of transcription factors for the Toll and IMD pathways and activation of detoxification enzymes. Fungal infection also led to a decrease in microbiota diversity, although the changes in community structure were not significant, except for the enhancement of Serratia. Fungal infection decreased the production of ROS but did not affect the gene expression of the immune pathways. In the combined treatment, fungal infection inhibited the activation of detoxification enzymes and prevented the downregulation of the JAK-STAT pathway caused by avermectins. The results of this study suggest that fungal infection modulates physiological responses to avermectins and that fungal infection may increase avermectin toxicosis by blocking detoxification enzymes in the gut.
... For example, the use of natural compounds with immunosuppressive effects may enhance the efficacy of microbial agents toward insect pests. We studied the effects of different microbial and plant metabolites (e.g., Streptomyces toxins, usnic acid derivatives, and Cordyceps extracts) as well as mixed infections on the defense systems and development of pathogeneses in different insects such as wax moth, CPB and four-eyed fir bark beetle Polygraphus proximus, and mosquito Aedes aegypti [35][36][37][38][39][40]. The synergy between pathogenic fungi (Metarhizium, Beauveria) and bacteria (B. ...
Stable and dynamic interactions among plants, herbivorous insects, parasites and associated microbes are formed in natural habitats. The study of these interactions in multicomponent models is required to develop integrated methods for the management of insect pest populations. In this work, we summarize our studies on the influence of different factors, such as hygrothermal conditions, host development, host microbiota, plant quality, and concomitant infections, on interactions between insects and their parasites, such as fungi, bacteria, viruses and parasitoids. Some approaches for developing complex products for biocontrol are also discussed. For example, the use of natural compounds with immunosuppressive effects may enhance the efficacy of microbial agents toward pest insects.
... Moreover, the additional load of cultivable bacteria in the gut promotes the development of fungal infection. Previously, many researchers considered mechanisms of synergy between entomopathogenic fungi and various intestinal or systemic toxicants (including parasitoid venoms) based on different changes in humoral and cellular immune reactions 35,[65][66][67][68][69][70] . However, the impact of the toxicants on microbial communities was insufficiently understood. ...
Gut bacteria influence the development of different pathologies caused by bacteria, fungi and parasitoids in insects. Wax moth larvae became more susceptible to fungal infections after envenomation by the ectoparasitoid Habrobracon hebetor. In addition, spontaneous bacterioses occurred more often in envenomated larvae. We analyzed alterations in the midgut microbiota and immunity of the wax moth in response to H. hebetor envenomation and topical fungal infection (Beauveria bassiana) alone or in combination using 16S rRNA sequencing, an analysis of cultivable bacteria and a qPCR analysis of immunity- and stress-related genes. Envenomation led to a predominance shift from enterococci to enterobacteria, an increase in CFUs and the upregulation of AMPs in wax moth midguts. Furthermore, mycosis nonsignificantly increased the abundance of enterobacteria and the expression of AMPs in the midgut. Combined treatment led to a significant increase in the abundance of Serratia and a greater upregulation of gloverin. The oral administration of predominant bacteria (Enterococcus faecalis, Enterobacter sp. and Serratia marcescens) to wax moth larvae synergistically increased fungal susceptibility. Thus, the activation of midgut immunity might prevent the bacterial decomposition of envenomated larvae, thus permitting the development of fungal infections. Moreover, changes in the midgut bacterial community may promote fungal killing.
This study evaluated the efficacy of the commercially available insecticide Lepidocide based on Bacillus thuringiensis var. kurstaki and Lymantria dispar multiple nucleopolyhedrovirus (LdMNPV) and their combination with an optical brightener to control L. dispar L. Efficacy against both second- and fourth-instar L. dispar larvae was evaluated, and the type of interaction between the tested components was determined using second-instar L. dispar larvae. Most combinations of Lepidocide and LdMNPV containing a 5 mg ml-1 optical brightener had synergistic effects, and their mixtures were most effective in reducing the number of second-instar larvae. In contrast, mixtures containing Lepidocide and LdMNPV with an optical brightener caused significantly lower mortality of fourth-instar L. dispar larvae than mixtures without Lepidocide. This result suggests that an increased concentration of Lepidocide in a mixture containing LdMNPV and an optical brightener leads to an antagonistic effect on insect mortality. The possible reasons for the differences in the observed effects of the components on the second- and fourth-instar L. dispar larvae may be associated with the resistance of fourth-instar larvae to the antifeedant effect of B. thuringiensis.
This review briefly summarizes the data on the virulence mechanisms of entomopathogenic ascomycetes and the defense reactions of insect hosts. Special attention is paid to the influence of environmental factors (temperature, toxicants, concomitant infections, symbiotic microorganisms and parasitoids) on the physiological aspects of
the relationship between insect hosts and entomopathogenic fungi. Based on our analysis, it may be supposed that prolonged influence of stress factors (low temperatures, natural and synthetic toxicants, bacterial infections) suppresses the set of cellular and humoral defense reactions and may also induce ontogenetic disorders in insects, thereby increasing their susceptibility to fungal infections. Understanding these mechanisms is important for the development of new approaches to biological control of economically important insect species.
Lichen, a distinct organism in plant kingdom, arises as a result of a symbiotic relationship between cyanobacteria and fungus. The medicinal use of lichen has been known in traditional systems including herbal, Chinese, and homeopathic medicines. The wide range of pharmacological activities and imaginable applications in medicinal and pharmaceutical chemistry in lichen are attributed to the presence of secondary metabolites like atranorin and usnic acid. They have been used for treating varied kidney diseases, arthritis, infections, leprosy, digestive and respiratory problems, and infestation and gynaecological issues. Several investigations on animals also proved lichens to possess antitumor, antibacterial, antiviral, analgesic, antipyretic, antiproliferative, antioxidant, and immunodilator activities. This review emphasizes the progress and development of lichens derived products in various biological activities with an update of current research findings.
p>The interaction between the entomopathogenic fungus Metarhizium robertsii and the pyrethroid insecticide esfenvalerate on Daphnia magna Straus was investigated. A synergy in the mortality of daphnids was detected after simultaneous treatment with sub-lethal doses of the fungus (1×10<sup>5</sup> conidia/ml) and esfenvalerate (0.1 mkg/l). The defense strategies of daphnids infected by fungus and treated with esfenvalerate and untreated insects were compared to investigate the mechanisms of this synergy. Activity of enzymes of the detoxification system and concentration of dopamine were measured. We have shown changes in the activities of the enzymes and dopamine concentration of daphnids under combined treatment of esfenvalerate and fungus. Fungus enhanced activity of glutathione-S-transferase and non-specific esterase but did not affect the dopamine level. Esfenvalerate inhibited the activity of enzymes in the detoxification system and cause a rise in dopamine level. We assume that the suppression of the detoxification system may be one of the reasons of synergy between M. robertsii and esfenvalerate.</p
