Most arthropod guts harbor diverse microbiota for symbiotic digestion. The European corn borer (ECB),
(Hübner), is a devastating pest that feeds the lignocellulose-rich tissues of maize plants. ...However, the potential role of ECB gut microbes in degrading maize cellulose remains largely unexplored. Here, we investigated the gut microbiota of ECB fed with different diets and their potential function in maize lignocellulose degradation. The diversity and composition of gut bacterial communities varied dramatically between the ECB larva fed with artificial diets (ECB-D) and maize plants (ECB-M). Draft genomes of the microbial consortia from ECB-D and ECB-M showed that the principal degraders of cellulose mainly belonged to Firmicutes or Proteobacteria and they were primarily found in the midgut. The cellulolytic microbial consortia contained genes encoding various carbohydrate-active enzymes (CAZyme). Furthermore, scanning electron microscopy revealed significant breakdown of lignocellulose in maize treated by the two microbial consortia for 9 days
. Metabolomic analyses show that maize particles treated by two microbial consortia generate distinctive metabolomic profiles, with enrichment for different monosaccharides (i.e., Glucose, Rhamnofuranose, Isomaltose, and Cellobiose) and amino acids (i.e., Threonine, Histidine, and Lysine). The results indicated that the diet of the host impacted the composition and function of its gut microbiota and ECB exploited specific gut microbes to digest maize lignocellulose with distinctive products. Our study provides valuable microbiota resources for lignocellulose bioconversion.
This work aimed to evaluate changes in phytic phosphorus content as the response of three maize hybrids (ZP 457, ZP 5601, and ZP 606) to different pesticide treatments for European Corn Borer (ECB) ...attacks and, as well as the correlation between damage caused by ECB attack and Pphy content. In the experimental field, maize ears were sampled and dried at a moisture content of 14% for the determination of changes in phytic phosphorus content in the grain. The content of phytic phosphorus was determined using UV / VIS spectrophotometry. Observed results showed the highest content of phytic phosphorus for untreated control for all tested hybrids, compared to pesticide treatments. The content of Pphy in the tested maize kernel samples ranged from 2.12 to 3.40 mg g-1. A significant positive correlation between attacks of larvae and Pphy content could indicate activation of its antioxidative function as a response to damage caused by ECB attack.
Maize with enhanced beta-carotene production was engineered to counteract pervasive vitamin A deficiency in developing countries. Second-generation biofortified crops are being developed with ...additional traits that confer pest resistance. These include crops that can produce Bacillus thuringiensis Berliner (Bt) insecticidal proteins. Currently, it is unknown whether beta-carotene can confer fitness benefits through to insect pests, specifically through altering Ostrinia nubilalis foraging behaviour or development in the presence of Bt insecticidal toxin. Therefore the effects of dietary beta-carotene plus Bt insecticidal protein on feeding behaviour, mortality, and physiology in early and late instars of O. nubilalis larvae were investigated. The results of two-choice experiments showed that irrespective of beta-carotene presence, at day five 68%-90% of neonates and 69%-77% of fifth-instar larvae avoided diets with Cry1A protein. Over 65% of neonate larvae preferred to feed on diets with beta-carotene alone compared to 39% of fifth-instar larvae. Higher mortality (65%-97%) in neonates fed diets supplemented with beta-carotene alone and in combination with Bt protein was found, whereas 36% mortality was observed when fed diets without supplemented beta-carotene or Bt protein. Diets with both beta-carotene and Bt protein extended 25 days the larval developmental duration from neonate to fifth instar (compared to Bt diets) but did not impair larval or pupal weight. Juvenile hormone and 20-hydroxyecdysone regulate insect development and their levels were at least 3-fold higher in larvae fed diets with beta-carotene for 3 days. Overall, these results suggest that the effects of beta-carotene and Bt protein on O. nubilalis is dependent on larval developmental stage. This study is one of the first that provides insight on how the interaction of novel traits may modulate crop susceptibility to insect pests. This understanding will in turn inform the development of crop protection strategies with greater efficacy.
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•The O. nubilalis orthologs of Ago2, Dcr2, and R2D2 were sequenced and characterized.•Transcripts of all three genes were detected in all stages and tissues.•Comparison of ...evolutionary distances for domains revealed significant variations.•Injection of dsGFP had no effect on Ago2, Dcr2, or R2D2 expression.•Ingestion of dsGFP could induce up/down-regulation of some transcripts.
RNA interference (RNAi) is commonly used in the laboratory to analyze gene function, and RNAi-based pest management strategies are now being employed. Unfortunately, RNAi is hindered by inefficient and highly-variable results when different insects are targeted, especially lepidopterans, such as the European corn borer (ECB), Ostrinia nubilalis (Lepidoptera: Crambidae). Previous efforts to achieve RNAi-mediated gene suppression in ECB revealed low RNAi efficiency with both double-stranded RNA (dsRNA) injection and ingestion. One mechanism that can affect RNAi efficiency in insects is the expression and function of core RNAi pathway genes, such as those encoding Argonaut 2 (Ago2), Dicer 2 (Dcr2), and a dsRNA binding protein (R2D2). To determine if deficiencies in these core RNAi pathway genes contribute to low RNAi efficiency in ECB, full-length complementary DNAs encoding OnAgo2, OnDcr2, and OnR2D2 were cloned, sequenced, and characterized. A comparison of domain architecture suggested that all three predicted proteins contained the necessary domains to function. However, a comparison of evolutionary distances revealed potentially important variations in the first RNase III domain of OnDcr2, the double-stranded RNA binding domains of OnR2D2, and both the PAZ and PIWI domains of OnAgo2, which may indicate functional differences in enzymatic activity between species. Expression analysis indicated that transcripts for all three genes were expressed in all developmental stages and tissues investigated. Interestingly, the introduction of non-target dsRNA into ECB second-instar larvae via microinjection did not affect OnAgo2, OnDcr2, or OnR2D2 expression. In contrast, ingestion of the same dsRNAs resulted in upregulation of OnDcr2 but downregulation of OnR2D2. The unexpected transcriptional responses of the core machinery and the divergence in amino-acid sequence between specific domains in each core RNAi protein may possibly contribute to low RNAi efficiency in ECB. Understanding the contributions of different RNAi pathway components is critical to adapting this technology for use in controlling lepidopteran pests that exhibit low RNAi efficiency.
RNA interference (RNAi) is a revolutionary technique for silencing gene expression, but the success of this technique is dependent upon the stability of double-stranded RNA (dsRNA) molecules. In many ...insects, especially lepidopteran species, RNAi efficiency is limited by high instability of dsRNA in the gut and/or hemolymph, preventing the development of RNAi-based strategies for many serious pests. Previous attempts to perform RNAi on Ostrinia nubilalis (ECB, Lepidoptera: Crambidae) indicate low RNAi efficiency with both dsRNA injection and feeding. To investigate the contribution of dsRNA instability to low RNAi efficiency in ECB, a serious of ex vivo incubation experiments were performed where dsRNA integrity was assessed following incubation in larval gut continents and hemolymph using gel electrophoresis or RT-qPCR. DsRNA was less stable in the gut contents from ECB than in gut contents from Diabrotica virgifera virgifera, a coleopteran exhibiting high RNAi efficiency. Furthermore, characterization of dsRNA stability in ECB gut contents and hemolymph revealed that dsRNA was rapidly degraded under physiologically relevant conditions as a result of enzymatic activity that was neither size- nor sequence-dependent. These findings suggest that instability of dsRNA in ECB tissues is a contributing factor to the poor efficiency of RNAi in this pest. This work advances our understanding of mechanisms impacting RNAi efficiency in ECB and related lepidopteran insects for which novel pest management strategies are needed, and may facilitate the development of strategies for enhancing dsRNA stability in ECB tissues.
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•DsRNA was highly unstable when incubated in gut contents of Ostrinia nubilalis larvae.•DsRNA was degraded under physiologically relevant pH conditions.•Degradation in gut contents and hemolymph was due to enzymatic activity.•Degradation of dsRNA was not size or sequence-dependent.
Na pojavu i štete od kukuruznog moljca kao jednog od najvažnijih štetnika kukuruza mogu utjecati različiti čimbenici. Istraživanje utjecaja sustava obrade tla i gnojidbe kukuruza na napad i štete od ...kukuruznog moljca provedeno je 2021. godine na pokusnim površinama Veleučilišta u Križevcima. Tretmani u pokusu bili su: standardna obrada tla (ST), konzervacijski sustav plitki (KSP) i konzervacijski sustav duboki (KSD), gnojidba prema preporuci (GPP), GPP s dodatkom biofoziološkog aktivatora (GPPGEO) te gnojidba umanjena za 50% (GU) i GU s dodatkom biofoziološkog aktivatora (GUGEO). Rezultati istraživanja su pokazali da sustav obrade tla, gnojidba kukuruza i njihove interakcije imaju značajan utjecaj na većinu, ali ne na sve mjerene parametre oštećenja od kukuruznog moljca (postotak zaraze stabljike, drške klipa i klipa, broj rupa i ukupna dužina oštećenja, broj gusjenica po biljci). Varijante ST, GPPGEO i GPP te njihove interakcije rezultirale su najvećim intenzitetom zaraze u većini parametara. Sustav obrade tla nije imao značajan učinak na postotak zaraze drške klipa, a gnojidba nije imala utjecaja na postotak zaraženih stabljika i broj gusjenica po biljci. Najveća masa klipa po biljci utvrđena je kod tretmana obrade tla KSP i ST, kod gnojidbe GPPGEO i GPP te u interakcijama KSP i GPP te ST i GPPGEO.
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•Several fungal metabolites co-occurring in maize for human consumption.•Overall, 25 Fusarium mycotoxins and metabolites were detected in NW-Italy maize.•The insecticide reduced FBs ...and other Fusarium spp. (Liseola section) mycotoxins.•The insecticide could increase DON and other Fusarium section Discolor metabolites.
Maize can be competitively colonized by several fungi that are capable of producing a variety of mycotoxins, mainly fumonisins B (FBs), with a negative impact on maize safety and quality.
The aim of this study was to investigate the impact of the insecticide application against European Corn Borer on the contamination of “emerging” mycotoxins and other fungal metabolites co-occurring with the legislated ones in maize for human consumption in North-West Italy from 2009 to 2015.
The insecticide application on average significantly increased the yield by 5%, and significantly reduced the ECB incidence and severity and the fungal ear rot incidence and severity compared to the untreated control.
Overall, 25 Fusarium mycotoxins and metabolites were detected. The results underline that the use of the insecticide, the most common FBs control practice in temperate areas on food maize, also resulted in significant reductions of other mycotoxins produced by Fusarium spp. of the Liseola section. However, this practice was not generally able to reduce the contents of Fusarium spp. section Discolor and Roseum mycotoxins. In environmental and agronomic conditions that favor deoxynivalenol and other metabolites produced by the previous mentioned Fusarium spp., the insecticide treatment could even increase their contamination.
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•The European Born Borer promote Fusarium infection and moniliformin contamination.•F. proliferatum is the main moniliformin producer in Italian maize temperate areas.•F. proliferatum ...shows a high toxigenic capacity related to moniliformin production.
The European Corn Borer (ECB), Ostrinia nubilalis (Hübner), plays an important role in promoting Fusarium infection and fumonisin production in maize kernels. Moniliformin (MON) is a mycotoxin that is usually found in association with fumonisins (FB), and as a consequence ECB is also expected to play a role in MON contamination.
The aim of the current study was to investigate the influence of ECB activity on MON contamination and on the fungi responsible for its contamination.
A comparison has been made between maize infected naturally by insect larvae and protected maize, from 2008 to 2010 in North–West Italy; the latter was obtained by positioning an entomological net at the end of maize flowering.
The Fusarium proliferatum infection of the maize grain was higher in each growing season than that caused by Fusarium subglutinans, although both species were significantly increased due to the ECB damage to the maize ears. The ECB activity significantly increased the MON content 26-fold in 2008 from 43 to 1137μgkg−1, 25-fold in 2009 from <LOQ to 77μgkg−1 and 94-fold in 2010 from 6 to 564μgkg−1. The relationship between the MON content and the Fusarium species producers of MON was closer for F. proliferatum (r=0.96, P<0.001) than for F. subglutinans (r=0.83, P<0.001). An in vitro assay was carried on in order to assess the toxigenic capacity of different F. proliferatum and F. subglutinans strains isolated from a field experiment and artificially inoculated on a maize substrate. On average, the F. proliferatum isolated strains showed a significantly higher (P<0.001) toxigenic capacity than the F. subglutinans strains.
In conclusion, the combination of the high toxigenic capacity of F. proliferatum, and its more frequent occurrence and greater intensity in the field make it possible to state that the production of MON in maize temperate areas, such as North Italy, is mainly due to F. proliferatum infections and is closely linked to the injury caused by ECB larvae.
Nanotechnology is a promising way to enhance the stability of
Bacillus thuringiensis
(Bt) insecticidal proteins under environmental conditions. In this work, two emulsions were prepared through the ...Pickering emulsion technique, stabilized by Cu
2+
-SQDs/S-CN nanocomposites and by GO nanosheets. In addition, a pH-sensitive polymer was incorporated into these emulsions, allowing the Bt protein, Cry1Ab, to be released in an alkaline pH environment, as it occurs in the lepidopteran pests’ gut. The effectiveness of these two nanomaterials in protecting Cry1Ab from degradation, and therefore enhancing its pesticidal activity, was assessed by exposing samples of the purified unprotected protein and encapsulated protein to high-intensity UV light and 40°C temperature treatments. The UV treatment results were evaluated using SDS-PAGE analysis and pointed out that Cry1Ab could be structurally protected by the emulsions. The bioassays with first instar larvae of the lepidopteran pest
Ostrinia nubilalis
confirm the nanomaterial protection to UV and temperature treatments, i.e., decreasing about half the degradation rate and increasing up to 12-fold the residual activity after UV treatment. Our results indicate that encapsulation could be an effective strategy to improve the effectiveness of Cry1Ab under environmental conditions.
Key points
•
Pickering emulsions are effective for solubilized Cry1Ab encapsulation.
•
Structural and toxicity Cry1Ab properties are enhanced by pH-sensitive encapsulation.
•
Cu
2+−
SQDs/S-CN and GO nanomaterials improve the efficacy of Bt insecticides.
![[beta]-carotene and Bacillu...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/1932-6203/small "[beta]-carotene and Bacillus thuringiensis insecticidal protein differentially modulate feeding behaviour, mortality and physiology of European corn borer (Ostrinia nubilalis).(Research Article)")
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