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1.
Bt cotton (Cry1Ac) has been commercially grown in China since 1997, saving China's cotton production from attack by Bt‐target pests and also tremendously reducing pesticide usage. In recent years, however, Bt cotton, with 4.2 million ha of cultivation, has suffered from a secondary target pest, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae). In China, growers have even had to re‐adopt conventional pesticides to control the pest, and this practice has already caused serious pesticide residue. In order to clarify the sublethal effects of chemical pesticide, the responses of a Bt‐susceptible and a Bt‐tolerant (Bt10) S. exigua strain to three treatment combinations were examined, including Bt toxin, sublethal chlorpyrifos, and Bt + sublethal chlorpyrifos. The susceptible and the Bt10 strain responded differently to dual pressure. Bt toxin + sublethal chlorpyrifos treatment lowered larval mortality and stimulated population increase of the susceptible S. exigua, whereas it delayed growth and development of the Bt10 strain. Under dual pressure, although larvae of the Bt10 strain developed faster than larvae of the susceptible strain, the Bt10 population experienced higher larval mortality, prolonged pupal duration, decreased pupal weight, decreased emergence rate, and shortened adult longevity. Compared with the susceptible strain, the Bt10 strain was deleteriously affected by sublethal chlorpyrifos. The Bt‐tolerant/resistant S. exigua population was more vulnerable to chemical pesticides like chlorpyrifos regardless of whether it was exposed to Bt toxin or not. Our study provides a reference for increasing the efficacy of control of S. exigua in Bt‐cotton planting areas.  相似文献   

2.
Polytrophic ovarioles of Spodoptera exigua, a lepidopteran insect, begins with the development of oocytes and differentiation of nurse cells followed by vitellogenesis and choriogenesis. Compared with previtellogenic and vitellogenic developments, choriogenesis has not been clearly understood yet in endocrine control. This study investigated the expression and function of a mucin‐like structural protein of S. exigua called Se‐Mucin1 in choriogenesis. It was highly expressed in ovarioles containing chorionated oocytes. The expression level of Se‐Mucin1 was increased during adult stage as early as 18 h after adult emergence, reaching the maximal level at 24 h and later. Interestingly, DNA amount of Se‐Mucin1 was increased by almost four folds during early adult stage while other genes (hexokinase and glyceraldehyde‐3‐phosphate dehydrogenase) not directly associated with chorion formation did not show genomic DNA increase, suggesting specific gene amplification of Se‐Mucin1. RNA interference (RNAi) suppressed Se‐Mucin1 expression by injecting 1 μg of double‐strand RNA to teneral females (<5 h after emergence), which exhibited significantly impaired fecundity and egg hatching rate. Eggs laid by RNAi‐treated females were malformed in eggshell structures with loss of mesh‐like fibers. Treatment with aspirin, a prostaglandin (PG) biosynthesis inhibitor, suppressed the induction of Se‐Mucin1 expression during early adult stage and impaired egg development. An addition of PGE2 significantly rescued such impairment in Se‐Mucin1 expression and subsequent egg development. These results suggest that PGs mediate choriogenesis of S. exigua by activating the expression of chorion‐associated genes including Se‐Mucin1.  相似文献   

3.
Insect pathogenic viruses and parasitoids represent distinct biological entities that exploit a shared host resource and have similar effects in suppressing host populations. This study explores the interactions between the ectoparasitoid Euplectrus plathypenae (Hymenoptera: Eulophidae) and the Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV) in larvae of S. exigua (Lepidoptera: Noctuidae). Parasitoid progeny failed to complete development in hosts that had been infected prior to parasitism. However, infection of S. exigua fourth instars at 48 h post‐parasitism had no significant effects on the survival of parasitoid progeny. Larval and pupal development times of E. plathypenae that survived on virus‐infected S. exigua did not differ significantly from that of parasitoids on healthy hosts. Virus‐induced mortality and the production of occlusion bodies were very similar in parasitized and non‐parasitized S. exigua. The virus was genetically stable over three passages in parasitized and unparasitized hosts. These results suggest that applications of SeMNPV‐based insecticides are unlikely to disrupt pest control exerted by the parasitoid E. plathypenae in biological pest control programs as long as virus applications are timed not to coincide with parasitoid releases.  相似文献   

4.
5.
Following the consumption of baculovirus occlusion bodies (OBs), insects may succumb to lethal disease, but the survivors can harbour sublethal covert infections and may develop, reproduce and transmit the infection to their offspring. The use of different chemical and biological stressors was examined to determine whether they could be used to activate covert infections in populations of Spodoptera exigua larvae infected by the homologous nucleopolyhedrovirus (SeMNPV). Treatment of covertly infected S. exigua second instars with Tinopal UNPA‐GX, hydroxylamine, paraquat, Bacillus thuringiensis var. kurstaki crystals, spores or mixtures of crystals + spores, or a heterologous nucleopolyhedrovirus (Chrysodeixis chalcites SNPV) did not result in the activation of SeMNPV covert infections. Similarly, virus treatments involving permissive NPVs did not result in greater mortality in covertly infected insects compared with the virus‐free controls. In contrast, 0.1% copper sulphate, 1% iron (II) sulphate and 1 mg/l sodium selenite treatments resulted in 12–41% lethal polyhedrosis disease in covertly infected larvae. A greenhouse trial using copper sulphate and sodium selenite as activation factors applied to covertly infected S. exigua larvae on sweet pepper plants resulted in very low levels of SeMNPV activation (<3%). These results highlight the important roles of copper, iron and selenium in insect immunity and baculovirus‐induced disease. However, these substances seem unlikely to prove useful for the activation of covert SeMNPV infections in S. exigua larvae under greenhouse conditions.  相似文献   

6.
Many parasites alter host behaviour to enhance their chance of transmission. Recently, the ecdysteroid UDP‐glucosyl transferase (egt) gene from the baculovirus Lymantria dispar multiple nucleopolyhedrovirus (LdMNPV) was identified to induce tree‐top disease in L. dispar larvae. Infected gypsy moth larvae died at elevated positions (hence the term tree‐top disease), which is thought to promote dissemination of the virus to lower foliage. It is, however, unknown whether egt has a conserved role among baculoviruses in inducing tree‐top disease. Here, we studied tree‐top disease induced by the baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV) in two different host insects, Trichoplusia ni and Spodoptera exigua, and we investigated the role of the viral egt gene therein. AcMNPV induced tree‐top disease in both T. ni and S. exigua larvae, although in S. exigua a moulting‐dependent effect was seen. Those S. exigua larvae undergoing a larval moult during the infection process died at elevated positions, while larvae that did not moult after infection died at low positions. For both T. ni and S. exigua, infection with a mutant AcMNPV lacking egt did not change the position where the larvae died. We conclude that egt has no highly conserved role in inducing tree‐top disease in lepidopteran larvae. The conclusion that egt is a ‘gene for an extended phenotype’ is therefore not generally applicable for all baculovirus–host interactions. We hypothesize that in some baculovirus–host systems (including LdMNPV in L. dispar), an effect of egt on tree‐top disease can be observed through indirect effects of egt on moulting‐related climbing behaviour.  相似文献   

7.
Beet armyworm, Spodoptera exigua (Hübner), is an economic pest of chickpea, Cicer arietinum L., in Mexico and the Indian subcontinent. Larvae feed on the vegetative and reproductive stages of chickpea and the development of plant resistance is a priority in the management of this pest. Forty‐two recombinant inbred lines (RILs) from a chickpea recombinant inbred line population (CRIL‐7) developed from a cross between FLIP 84‐92C (susceptible C. arietinum) and PI 599072 (resistant C. reticulatum Lad. accession) were rated resistant (nine lines with post‐trial larval weights 0.42–0.59 mg), moderately resistant/susceptible (25 lines, larval weights 0.61–0.99 mg) and susceptible (eight lines, larval weights 1.01–2.17 mg) to beet armyworm larvae in a general glasshouse screening. Resistance and susceptibility of entries (RILs in the CRIL‐7 population, parents, checks) was based on the average weight gain and fate of early‐stage larvae on pre‐flowering plants. In a growth chamber trial, early‐instar larval weight gain differed significantly (P < 0.0001) among entries (12 RILs, parents, checks), with mean weights from 0.80 mg (resistant RIL) to 4.03 mg (susceptible kabuli cultivar). There were no significant differences (P = 0.0836) in larval mortality among the entries in the growth chamber trial, although mortality rates were 28.2–61.9%. Flavonoid and isoflavonoid extractions and analyses did not clarify the role played by these phytochemicals in chickpea resistance to S. exigua. The requisite high levels of resistance to S. exigua and other pests for breeding resistant culivars may reside in the CRIL‐7 population.  相似文献   

8.

Background

The aims of this study were to develop and validate a multiplex real‐time polymerase chain reaction (q‐PCR) assay of Helicobacter pylori in stool samples of healthy children. Additionally, we determined the prevalence of clarithromycin resistance and cagA gene in H. pylori‐positive samples.

Materials and methods

Archived stool samples from 188 children aged 6‐9 years and 272 samples of 92 infants aged 2‐18 months were tested for H. pylori antigens using enzyme immunoassay (EIA). A multiplex q‐PCR assay was designed to detect H. pylori 16S rRNA and urease and the human RNase P gene as an internal control. Kappa coefficient was calculated to assess the agreement between q‐PCR and EIA.

Results

Laboratory validation of the q‐PCR assay using quantitated H. pylori ATCC 43504 extracted DNA showed S‐shaped amplification curves for all genes; the limit of detection was 1 CFU/reaction. No cross‐reactivity with other bacterial pathogens was noted. Applying the multiplex q‐PCR to DNA extracted from fecal samples showed clear amplification curves for urease gene, but not for 16S rRNA. The prevalence of H. pylori infection was 50% (95% CI 43%‐57%) by q‐PCR (urease cycle threshold <44) vs 59% (95% CI 52%‐66%) by EIA. Kappa coefficient was .80 (P < .001) and .44 (P < .001) for children aged 6‐9 years and 2‐18 months, respectively. Sixteen samples were positive for cagA and three were positive for clarithromycin resistance mutation (A2143G) as confirmed by sequencing.

Conclusions

The developed q‐PCR can be used as a cotechnique to enhance the accuracy of H. pylori detection in epidemiological studies and in clinical settings.  相似文献   

9.
Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV) and Microplitis pallidipes are both used as biocontrol agents of the beet armyworm (Spodoptera exigua). However, it has not been determined how beet armyworms respond when these agents interact. Here, we studied the effects of M. pallidipes on virus multiplication and transmission using quantitative detection of SeMNPV. Our results indicated that parasitoids promoted virus multiplication in caterpillars (105 copies per caterpillar) and that it was more advantageous when the M. pallidipes oviposited one day prior to infection with NPV. Interestingly, SeMNPV was transmitted by M. pallidipes in four ways. Transmission efficiency was higher for parasitoids whose body surfaces were contaminated with NPV, and for parasitoids ovipositing on NPV-infected caterpillars, than for those emerging from NPV-infected caterpillars, or feeding on mixtures of honey, water and NPV. Our study reveals that parasitoids do affect the proliferation and transmission of NPV in caterpillars and suggests that M. pallidipes could be used to strengthen the effectiveness of SeMNPV as a biocontrol agent.  相似文献   

10.
Chitin synthase (CHS) is an important enzymatic component, which is required for chitin formation in the cuticles and cuticular linings of other tissues in insects. CHSs have been divided into two classes, classes A and B, based on their amino acid sequence similarities and functions. Class A CHS (CHS‐A) is specifically expressed in the epidermis and related ectodermal cells such as tracheal cells, while class B CHS (CHS‐B) is expressed in gut epithelial cells that produce peritrophic matrices. In this study, we cloned the CHS‐A gene from the beet armyworm, Spodoptera exigua (SeCHS‐A). The SeCHS‐A contains an open reading frame of 4,698 nucleotides, encoding a protein of 1,565 amino acids with a predicted molecular mass of approximately 177.8 kDa. The SeCHS‐A mRNA was expressed in all developmental stages and specifically in the epidermis and tracheae tissue by quantitative real‐time‐PCR analysis. Expression of SeCHS‐A gene was suppressed by feeding double‐stranded RNA (dsCHS‐A, 400 ng/larva) in the third instar larvae of S. exigua. Suppression of the SeCHS‐A gene expression significantly increased 35% of mortality on pupation of S. exigua. Also, the third instar larvae fed with dsCHS‐A significantly increased susceptibility to entomopathogenic fungi, Beauveria bassiana ANU1 at 3 days after treatment. These results suggest that the SeCHS‐A gene plays an important role in development of S. exigua and RNA interference may apply to effective pest control with B. bassiana.  相似文献   

11.
Plants in nature have inducible defences that sometimes lead to targeted resistance against particular herbivores, but susceptibility to others. The metabolic diversity and genetic resources available for maize (Zea mays) make this a suitable system for a mechanistic study of within‐species variation in such plant‐mediated interactions between herbivores. Beet armyworms (Spodoptera exigua) and corn leaf aphids (Rhopalosiphum maidis) are two naturally occurring maize herbivores with different feeding habits. Whereas chewing herbivore‐induced methylation of 2,4‐dihydroxy‐7‐methoxy‐1,4‐benzoxazin‐3‐one glucoside (DIMBOA‐Glc) to form 2‐hydroxy‐4,7‐dimethoxy‐1,4‐benzoxazin‐3‐one glucoside (HDMBOA‐Glc) promotes caterpillar resistance, lower DIMBOA‐Glc levels favour aphid reproduction. Thus, caterpillar‐induced DIMBOA‐Glc methyltransferase activity in maize is predicted to promote aphid growth. To test this hypothesis, the impact of S. exigua feeding on R. maidis progeny production was assessed using seventeen genetically diverse maize inbred lines. Whereas aphid progeny production was increased by prior caterpillar feeding on lines B73, Ki11, Ki3 and Tx303, it decreased on lines Ky21, CML103, Mo18W and W22. Genetic mapping of this trait in a population of B73 × Ky21 recombinant inbred lines identified significant quantitative trait loci on maize chromosomes 1, 7 and 10. There is a transgressive segregation for aphid resistance, with the Ky21 alleles on chromosomes 1 and 7 and the B73 allele on chromosome 10 increasing aphid progeny production. The chromosome 1 QTL coincides with a cluster of three maize genes encoding benzoxazinoid O‐methyltransferases that convert DIMBOA‐Glc to HDMBOA‐Glc. Gene expression studies and benzoxazinoid measurements indicate that S. exigua ‐induced responses in this pathway differentially affect R. maidis resistance in B73 and Ky21.  相似文献   

12.
This study examined the physiological effects of joint and separate parasitism and infection by the endoparasitoid Microplitis pallidipes Szépligeti and the nucleopolyhedrovirus (NPV), respectively, on haemolymph 20‐hydroxyecdysone (20‐E) titre in Spodoptera exigua (Hübner) larvae. The results indicated that in parasitized larvae, virus‐infected larvae (5.7 × 103 and 5.7 × 105 OB/ml) and parasitized larvae infected with virus at 5.7 × 105 OB/ml, compared to healthy larvae, the 20‐E all declined during the first 3 days but began to increase from day 4 after treatment, while in jointly parasitized and infected larvae (5.7 × 103 OB/ml), the 20‐E declined during the first 4 days but began to increase on day 5 after treatment. Meanwhile, compared to parasitized larvae, the 20‐E declined during the first 4 days but significantly increased on day 5 in jointly parasitized and infected larvae (5.7 × 103 OB/ml), while significantly increased during the first 2 days but began to decrease from day 3 after treatment in jointly parasitized and infected larvae (5.7 × 105 OB/ml). Finally, in larvae that were both parasitized and virus infected (5.7 × 103 OB/ml), compared to just virus‐infected larvae (5.7 × 103 OB/ml), the 20‐E was lower on days 3 and 4 but higher on other days after treatment; in larvae that were both parasitized and virus infected (5.7 × 105 OB/ml), compared to just virus‐infected larvae (5.7 × 105 OB/ml), the 20‐E was significantly higher at the first 2 days but lower from day 3 after treatment. Our results revealed that 2nd instar larval M. pallidipes in host bodies may release 20‐E into the haemolymph of S. exigua larvae and that NPV infection may stimulate S. exigua to release more 20‐E during its third to fourth instar larval moulting. We found that this stimulatory effect was greater with higher virus concentrations.  相似文献   

13.
Allogeneic mesenchymal stem cell (MSC) transplantation improves cardiac function, but cellular differentiation results in loss of immunoprivilege and rejection. To explore the mechanism involved in this immune rejection, we investigated the influence of interleukin‐6 (IL‐6), a factor secreted by MSCs, on immune privilege after myogenic, endothelial and smooth muscle cell differentiation induced by 5‐azacytidine, VEGF, and transforming growth factor‐β (TGF‐β), respectively. Both RT‐PCR and ELISA showed that myogenic differentiation of MSCs was associated with significant downregulation of IL‐6 expression (P < 0.01), which was also observed following endothelial (P < 0.01) and smooth muscle cell differentiation (P < 0.05), indicating that IL‐6 downregulation was dependent on differentiation but not cell phenotype. Flow cytometry demonstrated that IL‐6 downregulation as a result of myogenic differentiation was associated with increased leucocyte‐mediated cell death in an allogeneic leucocyte co‐culture study (P < 0.01). The allogeneic reactivity associated with IL‐6 downregulation was also observed following MSC differentiation to endothelial and smooth muscle cells (P < 0.01), demonstrating that leucocyte‐mediated cytotoxicity was also dependent on differentiation but not cell phenotype. Restoration of IL‐6 partially rescued the differentiated cells from leucocyte‐mediated cell death. These findings suggest that rejection of allogeneic MSCs after implantation may be because of a reduction in cellular IL‐6 levels, and restoration of IL‐6 may be a new target to retain MSC immunoprivilege.  相似文献   

14.
Marek's disease (MD) is a neoplastic disease in chickens, caused by the Marek's disease virus (MDV). To investigate host genetic resistance to MD, we conducted a genome‐wide association study (GWAS) on 67 MDV‐infected chickens based on a case and control design, including 57 susceptible chickens in the case group and 10 resistant chickens as controls. After searching 38 655 valid genomic markers, two SNPs were found to be associated with host resistance to MD. One SNP, rs14527240, reaching chromosome‐wide significance level (< 0.01) was located in the SPARC‐related modular calcium‐binding 1 (SMOC1) gene on GGA5. The other one, GGaluGA156129, reaching genome‐wide significance (< 0.05), was located in the protein tyrosine phosphatase, non‐receptor type 3 (PTPN3) gene on GGA2. In addition, expression patterns of these two genes in spleens were detected by qPCR. The expression of SMOC1 was significantly up‐regulated (< 0.05), whereas the expression of PTNP3 did not show significance when the case group was compared with the control group. Up‐regulation of SMOC1 in susceptible spleens suggests its important roles in MD tumorigenesis. This is the first study to investigate MD‐resistant loci, and it demonstrates the power of GWASs for mapping genes associated with MD resistance.  相似文献   

15.
The beet armyworm Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) is a polyphagous insect that is distributed worldwide and was recently reported as an important pest on African indigenous vegetables. Cotesia icipe Fernandez‐Triana & Fiaboe (Hymenoptera: Braconidae) is a recently described parasitoid, reported from various Afrotropical countries. This work investigated the performance of C. icipe on S. exigua infesting Amaranthus dubius Mart. ex Thell. under laboratory conditions. Cotesia icipe was aggressive on the host and successfully oviposited on S. exigua with 70% of parasitoid females ovipositing after 2 hr of exposure. Parasitoid densities significantly affected the parasitism rate and the nonreproductive larval mortality. Parasitism rate was 9.7 ± 0.8% and 59.5 ± 3.1% for a single and cohort of five females released, respectively, when offered 50 host larvae. The cohort female release resulted in significantly higher larval nonreproductive mortality than the single release. However, there was no significant difference between parasitoid release densities in regard to pupal nonreproductive mortality. The larval and pupal mortalities in the presence of C. icipe were significantly higher than the natural mortalities at both parasitoid release densities. The parasitoid sex ratio was female‐biased for the cohort females but balanced when a single female was released. The hind tibia and forewing lengths were not affected by the density of female parasitoids but there were variations according to sex. The implication of these findings on the potential use of C. icipe for biological control of S. exigua in amaranth production systems is discussed.  相似文献   

16.
Trehalose is a major blood sugar in insects with a range of physiological functions, including an energy source and a cryoprotectant. Hemolymph trehalose concentrations are tightly regulated according to physiological conditions. An insulin‐like peptide, SeILP1, downregulates hemolymph trehalose concentrations in Spodoptera exigua. Here, we identified a factor that upregulates hemolymph trehalose concentration in S. exigua. Hemolymph trehalose concentrations were significantly increased after immune challenge or under starvation in a time‐dependent manner. To determine endocrine factors responsible for the upregulation, stress‐associated mediators, such as octopamine, serotonin, or eicosanoids were injected, but they did not upregulate hemolymph trehalose. On the other hand, injection with Schistocerca gregaria adipokinetic hormone (AKH) significantly increased hemolymph trehalose concentration in S. exigua. During upregulation of hemolymph trehalose by AKH injection, trehalose degradation appeared to be inhibited because expression of trehalase and SeILP1 were significantly suppressed while that of trehalose phosphate synthase was not significantly changed. Interrogation of a Spodoptera genome database identified an S. exigua AKH‐like gene and its expression was confirmed. During starvation, its expression concentrations were increased, although RNA interference specific to the AKH‐like hypertrehalosemic factor (SeHTF) gene significantly prevented the upregulation of hemolymph trehalose concentrations during starvation. A synthetic peptide of SeHTF was prepared and injected into S. exigua larvae. At nanomolar concentration, the synthetic SeHTF peptide effectively upregulated hemolymph trehalose concentrations. Here we report a novel hypertrehalosemic factor in S. exigua (SeHTF).  相似文献   

17.
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19.
We aimed to assess the feasibility of enhancing the intestinal development of weaned rats using glucagon‐like peptide‐2 (GLP‐2)‐expressing Saccharomyces cerevisiae (S. cerevisiae). GLP‐2‐expressing S. cerevisiae (GLP2‐SC) was generated using a recombinant approach. The diet of weaned rats was supplemented with the GLP2‐SC strain. The average daily gain (ADG), the intestinal morphology and the activities of the digestive enzymes in the jejunum were tested to assess the influence of the GLP2‐SC strain on intestinal development. The proliferation of rat enterocytes was also assessed in vitro. The study revealed that the ADG of the weaned rats that received GLP2‐SC was significantly greater than that of the controls fed a basal diet (Control) and S. cerevisiae harbouring an empty vector (EV‐SC) (P < 0.05) but was equivalent to that of positive control rats fed recombinant human GLP‐2 (rh‐GLP2) (P > 0.05). Furthermore, GLP2‐SC significantly increased villous height (P < 0.01) and digestive enzyme activity (P < 0.05) in the jejunum. Immunohistochemistry analysis further affirmed that enterocyte proliferation was stimulated in rats fed the GLP2‐SC strain, as indicated by the greater number of enterocytes stained with proliferative cell nuclear antigen (P < 0.05). In vitro, the proliferation of rat enterocytes was also stimulated by GLP‐2 expressed by the GLP2‐SC strain (P < 0.01). Herein, the combination of the GLP‐2 approach and probiotic delivery constitute a possible dietary supplement for animals after weaning.  相似文献   

20.
New anti‐infective approaches are much needed to control multi‐drug‐resistant (MDR) pathogens, such as methicillin‐resistant Staphylococcus aureus (MRSA). Here, we found for the first time that a recombinant protein derived from the cell wall binding domain (CBD) of the bacteriophage lysin PlyV12, designated as V12CBD, could attenuate S. aureus virulence and enhance host immune defenses via multiple manners. After binding with V12CBD, S. aureus became less invasive to epithelial cells and more susceptible to macrophage killing. The expressions of multiple important virulence genes of S. aureus were reduced 2.4‐ to 23.4‐fold as response to V12CBD. More significantly, V12CBD could activate macrophages through NF‐κB pathway and enhance phagocytosis against S. aureus. As a result, good protections of the mice from MRSA infections were achieved in therapeutic and prophylactic models. These unique functions of V12CBD would render it a novel alternative molecule to control MDRS. aureus infections.  相似文献   

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