Activity of the enzymes of the antioxidative system in cadmium-treated Oxya chinensis (Orthoptera Acridoidae)

Blue Light Exposure Caused Large-Scale Transcriptional Changes in the Abdomen and Reduced the Reproductive Fitness of the Fall Armyworm Spodoptera frugiperda

In the present study, we found that blue light stress negatively affected the development periods, body weight, survival and reproduction of Spodoptera frugiperda, and it showed a dose-dependent reaction, as longer irradiation caused severer effects. Further transcriptome analysis found blue light stress induced fast and large-scale transcriptional changes in the head, thorax and, particularly, the abdomen of female S. frugiperda adults. A functional enrichment analysis indicated that shorter durations of blue light irradiation induced the upregulation of more stress response- and defense-related genes or pathways, such as abiotic stimuli detection and response, oxidative stress, ion channels and protein-kinase-based signal pathways. In the abdomen, however, different durations of blue-light-exposure treatments all induced the downregulation of a large number genes and pathways related to cellular processes, metabolism, catalysis and reproduction, which may be a trade-off between antistress defense and other processes or a strategy to escape stressful conditions. These results indicate irradiation duration- and tissue-specific blue light stress responses and consequences, as well as suggest that the stress that results in transcriptional alterations is associated with the stress that causes a fitness reduction in S. frugiperda females.

Frankliniella occidentalis pathogenic fungus Lecanicillium interacts with internal microbes and produces sublethal effects

Frankliniella occidentalis (Thysanoptera: Thripidae) is a pest that feeds on various crops worldwide. A prior study identified Lecanicillium attenuatum and L. cauligalbarum as pathogens of F. occidentalis. Unfortunately, the potential of these two entomopathogenic fungi for the biocontrol of F. occidentalis has not been effectively evaluated. The internal microbes (endosymbionts and the gut microbiota) of insects, especially gut bacteria, are crucial in regulating the interactions between the host and intestinal pathogens. The role of thrips internal microbes in the infection of these two entomopathogenic fungi is also unknown. Therefore, biological control of thrips is immediately needed, and to accomplish that, an improved understanding of the internal microbes of thrips against Lecanicillium infection is essential. The virulence of the two pathogenic fungi against F. occidentalis increased with the conidia concentration. Overall, the LC50 of L. cauligalbarum was lower than that of L. attenuatum, and the pathogenicity degree was adult > pupa > nymphs. The activities of protective enzymes include superoxide dismutase (SOD), catalase (CAT), peroxidase (POD); detoxification enzymes include polyphenol oxidase (PPO), glutathione s-transferase (GSTs), and carboxylesterase (CarE); hormones include ecdysone and juvenile hormone; and the composition and proportion of microorganisms (fungi and bacteria) in F. occidentalis infected by L. cauligalbarum and L. attenuatum have changed significantly. According to the network correlation results, there was a considerable correlation among the internal microbes (including bacteria and fungi), enzyme activities, and hormones, which indicates that in addition to bacteria, internal fungi of F. occidentalis are also involved in the L. cauligalbarum and L. attenuatum infection process. In addition, the development time of the surviving F. occidentalis exposed to L. cauligalbarum or L. attenuatum was significantly shorter than that of the control group. Furthermore, the intrinsic rate of increase (rm), finite rate of increase (λ), net reproductive rate (R0), mean generation time (T), and gross reproductive rate (GRR) were significantly lower in the treatment groups than in the control group. L. attenuatum and L. cauligalbarum have biocontrol potential against F. occidentalis. In addition to bacteria, internal fungi of F. occidentalis are also involved in the infection process of insect pathogenic fungi. Disruption of the internal microbial balance results in discernible sublethal effects. Such prevention and control potential should not be ignored. These findings provide an improved understanding of physiological responses in thrips with altered immunity against entomopathogenic fungal infections, which can guide us toward the development of novel biocontrol strategies against thrips.

Effects of the Entomopathogenic Fungus Mucor hiemalis BO-1 on the Physical Functions and Transcriptional Signatures of Bradysia odoriphaga Larvae

Mucor hiemalis BO-1 is an entomopathogenic fungus that infects Bradysia odoriphaga, a destructive root maggot. M. hiemalis BO-1 possesses stronger pathogenicity to the larvae than to other stages of B. odoriphaga, and provides satisfactory field control. However, the physiological response of B. odoriphaga larvae to infection and the infection mechanism of M. hiemalis are unknown. We detected some physiological indicators of diseased B. odoriphaga larvae infected by M. hiemalis BO-1. These included changes in consumption, nutrient contents, and digestive and antioxidant enzymes. We performed transcriptome analysis of diseased B. odoriphaga larvae, and found that M. hiemalis BO-1 showed acute toxicity to B. odoriphaga larvae and was as toxic as some chemical pesticides. The food consumption of diseased B. odoriphaga after inoculation with M. hiemalis spores decreased significantly, and there was a significant decrease in total protein, lipid, and carbohydrates in diseased larvae. Key digestive enzymes (protease, α-amylase, lipase, and cellulase) were significantly inhibited during infection. Peroxidase maintained high activity, and the activity of other antioxidant enzymes (catalase, superoxide dismutase, and glutathione S-transferases) first increased and then decreased. Combined with the transcriptional signatures of diseased B. odoriphaga larvae, M. hiemalis BO-1 infection resulted in decreased food consumption, reduced digestive enzyme activity, and altered energy metabolism and material accumulation. Infection was also accompanied by fluctuations in immune function, such as cytochrome P450 and the Toll pathway. Therefore, our results laid a basis for the further study of the interactions between M. hiemalis BO-1 and B. odoriphaga and promoted the genetic improvement of entomopathogenic fungi.

Effects of Cu, Zn and their mixtures on bioaccumulation and antioxidant enzyme activities in Galleria mellonella L. (Lepidoptera: Pyralidae)

The effects of Cu, Zn and their mixture on bioaccumulation and antioxidant enzyme activities of midgut and fat body of Galleria mellonella larvae were investigated. Exposure to mixtures of both metals showed a synergistic effect and the accumulation levels were increased in both tissues. When the metals were exposed separately the concentration of Zn increased in both tissues, whereas the concentration of Cu increased in midgut and decreased in fat body. Also, it was determined that, oxidative stress occurred in the midgut and fat body when G. mellonella larvae were fed singly and in a mixture with different concentrations of Cu and Zn. In addition, significant changes were observed in antioxidant and detoxification enzyme activities, which are an indicator of oxidative stress. Larvae of G. mellonella showed immune responses similar to vertebrates, and could be used as bioindicator species due to being grown easily in the laboratory and reduced research costs Understanding the detoxification mechanism in insects is an important parameter for future ecotoxicological studies on the genotoxic, cytotoxic and physiological effects that different environmental pollutants such as heavy metals can cause.

Four alternative splicing transcripts of intracellular copper/zinc superoxide dismutase 1 in Oxya chinensis

In this study, we obtained four alternative splicing transcripts of intracellular copper/zinc superoxide dismutase 1 (icCuZnSOD1) in Oxya chinensis. OcicCuZnSOD1a has all common characteristics of CuZnSOD family and is a canonical CuZnSOD. OcicCuZnSOD1b is missing a Zn binding site. OcicCuZnSOD1c lacks Zn ion and is a Cu-only SOD. OcicCuZnSOD1d is missing a CuZnSOD conserved sequence and lacks the E-loop, a conserved disulfide bond, and an active site arginine. OcicCuZnSOD1a was the most heat-resistant and OcicCuZnSOD1c was the most unstable at high temperatures above 55 °C. They were stable at a wide pH range, especially in alkaline conditions. The four variants expressed at the throughout developmental stages and had various tissue expression patterns. OcicCuZnSOD1a and OcicCuZnSOD1d were significantly induced by 8.79 mM CuCl₂ and OcicCuZnSOD1b was significantly up-regulated by 14.67 mM CuCl₂. OcicCuZnSOD1a was significantly inhibited by 19.13 mM ZnSO₄ while OcicCuZnSOD1d were significantly induced by 22.61 mM ZnSO₄. Disc diffusion assay showed that the four isoforms of OcicCuZnSOD1 made the killing zones smaller surrounding the CdCl₂-soaked filter discs. However, the reduction ratios of OcicCuZnSOD1a were the highest. These results implied that the four transcripts played roles in defense against CdCl₂-induced oxidative stress while OcicCuZnSOD1a had stronger antioxidant capacity.

Biochemical and histological alterations induced by nickel oxide nanoparticles in the ground beetle Blaps polychresta (Forskl, 1775) (Coleoptera: Tenebrionidae)

The present study evaluates the effect of nickel oxide nanoparticles on some biochemical parameters and midgut tissues in the ground beetle Blaps polychresta as an indicator organism for nanotoxicity. Serial doses of the NiO-NPs colloid (0.01, 0.02, 0.03, 0.04, 0.05, and 0.06 mg/g) were prepared for injecting into the adult beetles. Insect survival was reported daily for 30 days, and the sublethal dose of 0.02 mg/g NiO-NPs was selected for the tested parameters. After the treatment, nickel was detected in the midgut tissues by X-ray microanalysis. The treated group demonstrated a significant increase in aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities when compared to the untreated group. However, the treated group demonstrated a significant decrease in ascorbate peroxidase (APOX) activity when compared to the untreated group. Histological and ultrastructural changes in the midgut tissues of treated and untreated beetles were also observed. The current findings provide a precedent for describing the physiological and histological changes caused by NiO-NPs in the ground beetle B. polychresta.

Phototoxicity of Ultraviolet-A against the Whitefly Bemisia tabaci and Its Compatibility with an Entomopathogenic Fungus and Whitefly Parasitoid

Ultraviolet (UV) radiation significantly affects insect life and, as a result, has been widely used to control different invertebrate pests. The current results demonstrate that when Bemisia tabaci first instar nymphs are exposed to UV-A light for 12, 24, 48, and 72 h, their developmental and biological parameters are negatively affected by UV-A exposure; the effect increased with an increase in exposure time. We hypothesized that UV-A light is compatible with other biological control agents. Results showed that when the entomopathogenic fungus Cordyceps fumosorosea was applied to third instar nymphs of B. tabaci previously exposed to UV-A light, the LC50 was 3.4% lower after 72 h of exposure to UV-A light compared to the control. However, when the fungus was exposed to UV-A light, its virulence decreased with an increase in UV-A exposure time. The parasitism rate of Encarsia formosa against 24 h UV-A-exposed third instar nymphs of B. tabaci increased while the adult emergence from parasitized nymphs was not affected after UV-A light exposure. Parasitism rate was significantly reduced however following E. formosa exposure to UV-A light; but again, adult emergence was not affected from parasitized nymphs. The percentage mortality of E. formosa increased with increasing exposure time to UV-A light. The enzyme activity of SOD, CAT, GST, and AChE and the energy reserve contents were negatively affected due to UV-A exposure. Collectively, this study has demonstrated that UV-A light significantly suppresses the immune system of B. tabaci and that UV-A light is compatible with other biological control agents if it is applied separately from the biological agent.

Effects of Selenium and Vitamin E on Enzymatic, Biochemical, and Immunological Biomarkers in Galleria mellonella L

To understand the effects of micronutrients have particular biological functions that are involved mainly in the antioxidant system, which has essential implications for the development of diseases, this study investigated how vitamin E, selenium, and their combination affect lipid, protein, carbohydrate, and malondialdehyde (MDA) content; antioxidant enzyme (catalase [CAT], superoxide dismutase [SOD], glutathione-S-transferase [GST]) activity; and the total hemocyte count (THC) in larvae of Galleria mellonella L. fed different diets. Diet 1 (100 µg of selenium) significantly decreased carbohydrate and lipid content. Diets 2 (100 µg of vitamin E), 3 (100 µg of selenium and vitamin E each), and 5 (Tween 80) did not significantly affect protein and carbohydrate content. Diet 2 significantly increased the lipid content compared to diet 4 (control). Diet 1 increased CAT, SOD, and GST activity and MDA content (highest at 27.64 nmol/mg protein). Diet 2 significantly decreased SOD activity and MDA content compared to other diets. Diet 1 significantly decreased the THC compared to other diets. These results suggested that selenium changes oxidative stress parameters, energy reserves, and THC in G. mellonella. These changes could be a physiological adaptation against selenium-induced oxidative stress. Vitamin E could play a protective role in selenium toxicity.

A second intracellular copper/zinc superoxide dismutase and a manganese superoxide dismutase in Oxya chinensis: Molecular and biochemical characteristics and roles in chlorpyrifos stress

A second intracellular copper/zinc superoxide dismutase (icCuZnSOD2) and manganese SOD (MnSOD) were cloned and characterized in Oxya chinensis. The open reading frame (ORF) of OcicCuZnSOD2 and OcMnSOD are 462 and 672 bp encoding 153 and 223 amino acids, respectively. OcicCuZnSOD2 contains two signature sequences, one potential N-glycosylation site, and seven copper/zinc binding sites. OcMnSOD includes a mitochondria targeting sequence of 7 amino acids at N-terminal, one signature sequence, two N-glycosylation sites, and four manganese binding sites. The secondary structure and homology model of OcicCuZnSOD2 include nine β sheets, two Greek-key motifs, and one electrostatic loop. OcMnSOD contains nine α-helices and three β-sheets. Phylogenetic analysis shows that OcMnSOD is evolutionarily conserved while OcicCuZnSOD2 may be gene duplication and is paralogous to OcicCuZnSOD1. OcMnSOD expressed widely in all tissues and developmental stages. OcicCuZnSOD2 showed testis-specific expression and expressed highest in the 5th-instar nymph and the adult. The optimum temperatures and pH values of the recombinant OcicCuZnSOD2 and OcMnSOD were 40 °C and 8.0. They were stable at 25-55 °C and at pH 5.0-12.0 and pH 6.0-12.0, respectively. The activity and mRNA expression of each OcSOD were assayed after chlorpyrifos treatments. Total SOD and CuZnSOD activities first increased then declined under chlorpyrifos stress. Chlorpyrifos induced the mRNA expression and activity of OcMnSOD as a dose-dependent manner and inhibited OcicCuZnSOD2 transcription. The role of each OcSOD gene in chlorpyrifos stress was investigated using RNAi and disc diffusion assay with Escherichia coli overexpressing OcSOD proteins. Silencing of OcMnSOD significantly increased ROS content in chlorpyrifos-exposed grasshoppers. Disc diffusion assay showed that the plates with E. coli overexpressing OcMnSOD had the smaller inhibition zones around the chlorpyrifos-soaked filter discs. These results implied that OcMnSOD played a significant role in defense chlorpyrifos-induced oxidative stress.

Comparative efficacy of two mycotoxins against Spodoptera litura Fab. And their non-target activity against Eudrilus eugeniae Kinb

Entomopathogenic fungi are feasible and effective against the agricultural pest. In the current research we investigated the bioactive comparison of two widely accepted entmopathogens (Beauveria bassiana (Bals.) Vuill. and Metarhizium anisopliae, (basionym)) against the Spodoptera litura (Fab.) through the assessment of larval tolerance and regulation of antioxidants and non-target impact on the earth worm, E. eugeniae, along with commercial pesticides. The entomopathogenic fungus exposure resulted in the modification of the levels of detoxification enzymes as well as significant increases in catalase and superoxide dismutase activity after exposure to the entomopathogenic fungus. Bioassay results showed that B. bassiana and M. anisopliae displayed larval mortality against third and fourth instars. Correspondingly, sub-lethal concentrations of B. bassiana showed development impairment as compared to M. anisopliae. Gut-histology revealed that mycotoxins dosage (4 × 10⁵) showed significant changes in the midgut tissues as compared to control larvae. The non-target screening through artificial soil assay on the earth worm E. eugeniae, with mycotoxins B. bassiana (5 × 10⁸ conidia/ml/kg) and M. anisopliae (5 × 10⁸ conidia/ml/kg) showed less toxicity as compared to Monocrotophos (10 ppm/kg). Current results suggest that the fungal mycotoxins of M. anisopliae and B. bassiana significantly reduce the development of lepidopteran pests, while having only lesser impact on beneficial earthworms.

Antioxidant enzyme activity in responses to environmentally induced oxidative stress in the 5th instar nymphs of Aiolopus thalassinus (Orthoptera: Acrididae)

The response of antioxidant enzymes to oxidative environmental stress was determined in 5th instar nymphs of Aiolopus thalassinus (Orthoptera: Acrididae) collected from sites with different level of pollution with heavy metals, PO₄^3-, and SO₄^2-. The high polluted site induced higher DNA damage to individuals compared to the control site. The highest values of tail length (TL), tail moment (TM), and percent of DNA in tail (TDNA) were found in the gut of 5th instar nymphs from a high polluted site. Also, protein carbonyls and lipid peroxide levels were significantly higher in insects collected from polluted sites compared to those from the control site. A strong positive correlation between both protein carbonyl and lipid peroxide concentration and the pollution level of the sites was found in all tissues of the insects. The activity of superoxide dismutase (SOD) in the brain of insects collected from the high polluted site was significantly higher than that in the thoracic muscles and gut. We observed strong inhibition of catalase (CAT) activity. This effect was apparently caused by pollutants present at the high polluted site. The level of pollution significantly influenced polyphenol oxidase (PPO) activity in A. thalassinus nymphs in all examined tissues. The highest values were observed in the brain. The relationship between pollution and ascorbate peroxidase (APOX) activity in the examined tissues had no clear tendency. However, the lowest APOX activity was observed in individuals from the low polluted site. Level of pollution of sampling sites, oxidative stress biomarkers, and enzymatic response in A. thalanthsis 5th instar were negatively or positively correlated. Oxidative damage parameters, especially the percent of severed cells, lipid peroxides, and the activity of APOX, can be perceived as good markers of environmental multistress.

Antioxidant defenses at enzymatic and transcriptional levels in response to acute lead administration in Oxya chinensis

Lead (Pb) is known to be toxic to many organisms. Oxidative stress is a major mechanism of its toxicity. This research aims to investigate the effects of Pb on hydrogen peroxide (H₂O₂) and malonedialdehyde (MDA) contents, activities and mRNA levels of antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx)) after Oxya chinensis were acutely treated with lead acetate for 24 h. The results showed that the LD₅₀-24 h value of lead acetate to O. chinensis was 1541.89 (1431.19-1655.77) μg g^-1 body H₂O₂ and MDA contents were elevated after Pb administration, which suggested that Pb induced the overproduction of ROS and caused oxidative stress. SOD activities were significantly inhibited 40.42% of the control by 280 μg μL^-1 Pb. CAT activities were increased while GPx activities had no significant changes. Different types of antioxidant-related genes had various responses to Pb stress. The transcriptions of icCuZnSOD2 and ecCuZnSOD2 were significantly inhibited by different concentrations of Pb. MnSOD mRNA levels showed the concentration-dependent rise with the Pb concentrations increase. The expressions of ecCuZnSOD1, CAT1, and GPx were significantly up-regulated while the transcriptions of icCuZnSOD1 and CAT2 had no significant changes. Alteration of activities and mRNA expressions of antioxidant enzymes implied that Pb-induced antioxidant defenses were related to modifications at enzymatic and transcriptional levels. The profiles of antioxidant enzymes and H₂O₂ and MDA contents and relationships among the parameters indicated that the cooperation of multiple antioxidants rather than a single factor might be responsible for the antioxidant defenses against Pb stress.

Aspergillus flavus (Link) toxins reduces the fitness of dengue vector Aedes aegypti (Linn.) and their non-target toxicity against aquatic predator

Mosquito that accountable for dispersal of dengue fever is Aedes aegypti Linn. and considered to be a chief vector for dengue especially in South Asian countries. Aspergillus flavus is considered to be wild growing green yellow colonies and synthesis highly regulating aflatoxins (B1, B2, G1 and G2) as a secondary metabolite. Mycotoxins of A. flavus showed its efficacy against III and IV instars of Ae. aegypti with more than 90% mortality at the prominent dosage of 2 × 10⁸ conidia/ml. The proximate lethal concentrations (LC₅₀ and LC₉₀) of mycotoxins against third and fourth instars was 2 × 10⁵ and 2 × 10⁷ respectively. Correspondingly, sub-lethal dosage of mycotoxin A. flavus significantly inhibited the level of α- β-carboxylesterase and SOD activity and upregulated the level of major detoxifying enzymes GST and CYP450. Moreover, sub-lethal dosage also showed higher deterrent and fecundity effects. Gut-histological examination reveals that the A. flavus considerably affected the gut epithelial cells along with the inner gut lumen as compared to the control. The non-target screening of A. flavus against two aquatic predators (A. bouvieri and Tx. splendens) display more than 80% of mortality rate against both the species at the dosage of 2 × 10¹⁶ (two-fold-higher dosage used in larval assays). Thus the biosafety assessment suggests that A. flavus display higher toxicity against the non-targets and it is not-recommended to apply it directly to the aquatic habitat of dengue mosquito which shares their living space with other beneficial insects.

Role of a serine protease gene (AccSp1) from Apis cerana cerana in abiotic stress responses and innate immunity

Clip-domain serine proteases (Clip-SPs) mediate innate immunity and embryonic development in insects. However, the function of Clip-SPs in Apis cerana cerana is little known. Here, a Clip-SP gene, AccSp1, was identified. AccSp1 was mainly detected in third and sixth day instar larvae, dark-eyed pupae, and adults (1and 30 days post-emergence). In addition, AccSp1 was expressed at its highest level in the venom gland and epidermis than tentacle, abdomen, muscle, honey sac, head, leg, chest, hemolymph, rectum, and midgut. AccSp1 was induced by 4, 24, and 44 °C; H2O2; CdCl2; HgCl2; and pesticides (paraquat, pyridaben, and methomyl) and was inhibited by UV light and cyhalothrin treatments. When adults that had been pretreated with dsRNA 6 h prior (knocking AccSp1 down) were challenged with Bacillus bombysepticus for 18 h, the survival rate of bees greatly decreased, the activity of PO (phenoloxidase) was reduced, revealing that AccSp1 may play a critical role in assisting bees to survive the microbial infection and participate in regulating PO activity. The antioxidant enzymatic activities of catalase, peroxidase, and superoxide dismutase; the contents of hydrogen peroxide and malondialdehyde; and the ratio of NADP+/NADPH were all lower in samples containing dsRNA-AccSp1 interference than in control groups, but the content of carbonyl was not significantly different. These findings suggest the knockdown of AccSp1 may influence melanization so that the antioxidant enzyme activities and the harmful metabolites decreased. These results collectively suggest that AccSp1 plays critical roles in abiotic stresses responses and resistance to pathogens.

Evaluation of oxidative stress biomarkers in the freshwater gammarid Gammarus dulensis exposed to trout farm outputs

The current study reports a combined seasonal monitoring of the Crnica River watercourse using physico-chemical parameters and biomarkers measured in Gammarus dulensis with the aim of correlating the effects of pollution with the level of oxidative stress biomarkers in this amphipod. The pollution source is identified as a trout farm in the upper part of the Crnica River (Eastern Serbia). Physico-chemical water parameters and sediment trace element concentrations were measured in the Crnica River during three seasons. Three localities downstream [CR2, CR3, and CR4 (20 m, 400 m, and 1.3 km from the trout farm discharge, respectively)] were assessed in comparison with a reference location (CR1), 250 m upstream from the trout aquaculture in the Crnica River. Antioxidant biomarkers including the enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathione reductase (GR), and glutathione-S-transferase (GST) were determined in pooled samples of G. dulensis. Our findings showed statistically different antioxidant enzyme levels in gammarids from the first downstream locality (CR2) compared to those from other three localities. The results indicate that oxidative stress occurred to some extent despite the assumed antioxidant induction as a result of exposure to elevated levels of some elements and changed water parameters, the effects seeming in part to be mediated by suppression of SOD and CAT (during summer and autumn); and by suppression of GPX and GR (during autumn) at the CR2 locality. The activity of GST in all seasons was higher at the CR2 locality than at the other localities, suggesting the presence of some permanent xenobiotic next to the aquaculture output. Seasonal difference in the physical and chemical water parameters and sediment trace element concentrations were observed. Overall, our results indicate a locality- and season-dependent antioxidant enzymes response in G. dulensis, pointing at progressively reduced deleterious effect of trout farm outputs with movement further downstream.

Influence of metal-contamination on distribution in subcellular fractions of the earthworm (Metaphire californica) from Hunan Province, China

Earthworms have the ability to accumulate of heavy metals, however, there was few studies that addressed the metals in earthworm at subcellular levels in fields. The distributions of metals (Cd, Cu, Zn, and Pb) in subcellular fractions (cytosol, debris, and granules) of earthworm Metaphire californica were investigated. The relationship between soil metals and earthworms were analyzed to explain its high plasticity to inhabit in situ contaminated soil of Hunan Province, south China. The concentration of Cd in subcellular compartments showed the same pattern as Cu in the order of cytosol > debris > granules. The distribution of Zn and Pb in earthworms indicated a similar propensity for different subcellular fractions that ranked as granules > debris > cytosol for Zn, and granules > cytosol > debris for Pb. The internal metal concentrations in earthworms increased with the soil metals (p<0.05). Significant positive correlations were found between soil Cd and Cd concentrations in cytosol and debris (p<0.01). Moreover, the soil Pb concentration significantly influenced the Pb concentrations in cytosol and debris (p<0.01), similar to that of Cd. The soil Cu concentrations was only associated with the Cu in granules (p<0.05). Soil Zn concentrations correlated with the Zn concentrations in each subcellular fraction (p<0.05). Our results provide insights into the variations of metals partitioning in earthworms at subcellular levels and the relationships of soil metals, which could be one of the detoxification strategies to adapt the long-term contaminated environment.

Effect of Aspergillus flavus on the mortality and activity of antioxidant enzymes of Spodoptera litura Fab. (Lepidoptera: Noctuidae) larvae

Insects have developed tolerance against mycoses caused by entomopathogenic fungi through several humoral and cellular mechanisms. Antioxidant enzymes such as superoxide dismutase, lipid peroxidase, and peroxidase can play a role in defense against mycosis, but the physiological interactions between the fungus and the insect are not well characterized. In this study, the effects of infection by entomopathogenic fungus, Aspergillus flavus on the antioxidant defense system of Spodoptera litura, were investigated. The fungi, A. flavus exposure resulted in modification of the levels of antioxidant enzymes, as well as significant decline in phenoloxidase titers and the total hemocyte count 48 h post exposure. A significant increase was observed in detoxifying enzymes. All these results suggest that A. flavus infects S. litura by directly acting on the immune system, resulting in decreased immune function. Bioassay results showed that A. flavus affects third and fourth instar larvae of S. litura. This report supports the importance of A. flavus as a candidate for biological control of S. litura.

Effects of Cd accumulation on cutworm Spodoptera litura larvae via Cd treated Chinese flowering cabbage Brassica campestris and artificial diets

By exposing herbivorous cutworm Spodoptera litura (Lepidoptera: Noctuidae) larvae to Cadmium (Cd) stress via Cd treated cabbages Brassica campestris and artificial diets, we investigated effects of Cd accumulation in larvae on their survival and food utilization. The results showed that Cd transferred from soils contaminated with different Cd concentrations through cabbages-larvae, and be mainly accumulated in larvae guts. There was a dose-response relationship between Cd accumulations in larvae cuticle, head, guts and Cd concentrations in artificial diets, and the highest one was found in the guts, regardless of generations. High Cd stress (10 mg kg^-1 Cd in soil, 40.6, 81.2 mg kg^-1 Cd in artificial diets) had inhibited effects on larvae growth and food utilization, whereas low Cd stress (Lvbao 701 planted in 2.5 mg kg^-1 Cd soil, 4.06 mg kg^-1 Cd in artificial diets) showed stimulated effect. Cd accumulations in the guts were significantly negative correlated with efficiency of conversion of ingested food (ECI) and relative growth rate (RGR) of larvae feeding on Cd treated diets or cabbages while were significantly positive correlated with relative consumption rate (RCR). Therefore, after S. litura larvae feed on Cd treated natural food or artificial diets, Cd could be transferred to different tissues, and mainly accumulated in the guts, which significantly affected growth and food utilization. Additionally, Cd stress via Cd treated artificial diets presented less detrimental effects on S. litura larvae than via Cd treated cabbages.

The initial analysis of a serine proteinase gene (AccSp10) from Apis cerana cerana: possible involvement in pupal development, innate immunity and abiotic stress responses

Serine proteinases play important roles in innate immunity and insect development. We isolated a serine proteinase gene, designated AccSp10, from the Chinese honeybees (Apis cerana cerana). RT-qPCR and a Western blot analysis at different pupal development stages indicated that AccSp10 might be involved in melanin formation in pupae and promote pupal development. In adult workers, the expression of AccSp10 was upregulated by treatments mimicking harmful environments such as the presence of Bacillus bombysepticus, different temperatures (4, 24 and 42 °C), HgCl2, H2O2 and paraquat; the exception was treatment with VC (vitamin C), which did not upregulate AccSp10 expression. Western blot confirmed the results. A disc diffusion assay indicated that recombinant AccSp10 accelerated E. coli cell death during stimulation with harmful substances (HgCl2, paraquat and cumene hydroperoxide). These findings suggest that AccSp10 may be involved in the pupal development of Chinese honeybees and protection against microorganisms and abiotic harms.

Overexpression of Mn-superoxide dismutase in Oxya chinensis mediates increased malathion tolerance

Superoxide dismutase (SOD) is the first line of defense against oxidative damage. Malathion is an organophosphate insecticide and can induce the production of reactive oxygen species (ROS) and cause the intracellular oxidative stress. The present study was undertaken to examine the effects of malathion on SODs activity and their transcriptional levels in Oxya chinensis (Thunberg) (Orthoptera: Acrididae). The results showed that total SOD and MnSOD activities increased as a dose-dependent manner while CuZnSOD activity has no significant changes after malathion treatments. Total SOD and MnSOD activities were the highest at the concentration of 0.8 μg μL^-1 malathion treatment and increased significantly about 1.81- and 2.48-fold compared with the control, respectively. Increased mRNA expression of MnSOD, ecCuZnSOD1, and ecCuZnSOD2 were observed after malathion treatments. Moreover, the alteration of MnSOD transcript was similar to the profiles of MnSOD activity. These results suggested that the up-regulation expression of MnSOD transcript led to the increase of MnSOD activity in order to eliminate the excessive ROS caused by malathion. In addition, we evaluated the role of individual SOD gene in malathion stress by using RNAi and recombinant SOD proteins. The results showed that ROS contents increased significantly after the silencing of MnSOD and ecCuZnSOD1 genes. The OD values of the E. coli cells transformed with pET-28a-OcMnSOD plasmid were 1.13-1.31-fold and 1.08-1.33-fold higher than those of cells with pET-28a plasmids under 0.4 and 0.8 μg μL^-1 malathion treatments, respectively. These findings indicated that MnSOD exerted an important role in defense oxidative stress caused by malathion.

Evaluation of oxidative stress biomarkers in Aiolopus thalassinus (Orthoptera: Acrididae) collected from areas polluted by the fertilizer industry

The waste products of the fertilizer industry such as heavy metals, but especially phosphates and sulphates, are a serious problem that influences the structure and functioning of ecosystems. The levels of Cd, Pb, Zn, Cu, sulphates and phosphates were measured in soil samples from four sites: a control and sites that were 1, 3 and 6 km (sites A-C) away from the Abu-Zaabal Fertilizer Company. Oxidative stress markers (protein carbonyls, lipid peroxides), antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), polyphenoloxidase (PPO) and ascorbate peroxidase (APOX)) were evaluated in the tissues of Aiolopus thalassinus, collected from the corresponding sites. The highest concentrations of Cu and Zn were found in the soil from site A. The level of protein carbonyls in the brain, thoracic muscles and gut of the males and females from sites A, B and C were 11.82, 4.38, 5.97 (males) and 19.04, 16.65, 7.79 (females) times higher, respectively, compared to the individuals from the control site. Lipid peroxides levels in both sexes were significantly correlated with the distance from the source of the contamination. In the brain, thoracic muscles and gut of the males and females collected from site A, the level of lipid peroxides were 15.41, 23.49, 11.50 (males) and 25.36, 11.34, 15.37 (females) times higher compared to the values of the control animals. The activities of SOD, PPO, CAT and APOX were significantly affected by the environmental pollutants. The enzymatic and non-enzymatic oxidative markers in the Aiolopus thalassinus, a common insect species that inhabits various ecosystems, can also be used as a relevant biomarker of the pollution that is caused by the fertilizer industry.

Assessment of the effects of orally administered ferrous sulfate on Oncopeltus fasciatus (Heteroptera: Lygaeidae)

Iron is an essential nutrient needed for multiple biological processes, but it is also an effective pro-oxidant in its reduced form. Environmental sources of iron toxic species include reduced soils from rice plantations, polluted natural areas from metal industry waste, or iron oxides used in soil bioremediation. Few studies have been conducted to assess the toxicity of iron species in insects. The present work aims to assess the oxidative stress effects of ferrous sulfate administered in drinking water after acute exposure (96 h) to adults of the insect model Oncopeltus fasciatus (Dallas). Mortality was higher in exposed groups and significantly associated with iron treatment (OR [95% CI]; 11.8 [6.1-22.7]). Higher levels of body iron content were found in insects exposed to ferrous sulfate, with an increase of 5-6 times with respect to controls. Catalase activity and lipid peroxidation (TBARS content), but not glutathione S-transferase activity, were significantly higher in exposed insects and significantly correlated with body iron content (Pearson coefficient of 0.68 and 0.74, respectively) and between them (0.78). The present work demonstrates that, despite the disruption in water and food intake caused by iron administration, this metal is accumulated by insect causing lipid peroxidation and eliciting an antioxidant response mediated by catalase.

Influence of UV-A radiation on oxidative stress and antioxidant enzymes in Mythimna separata (Lepidoptera: Noctuidae)

Abiotic stress factors, including ultraviolet (UV) radiation, significantly affect insect life. UV-A radiation (320-400 nm) has been widely used for insect control since it increases the production of ROS and causes oxidative cell damage. In the present study, we evaluated the effects of UV-A irradiation on an important pest in China, the ear-cutting caterpillar, Mythimna separata (Lepidoptera: Noctuidae). We exposed 3-day-old M. separata adults to UV-A radiation for different periods of time (0, 30, 60, 90, and 120 min) and evaluated the resulting total antioxidant capacity and the activity of the antioxidant enzymes superoxide dismutase, catalase, peroxidase, and glutathione-S-transferase. The total antioxidant capacity significantly increased after exposure to UV-A radiation for 60 min but decreased after 90 and 120 min of exposure, compared with the control. The antioxidant activity of glutathione-S-transferase, superoxide dismutase, catalase, and peroxidase increased after 60-min exposure, and it was decreased at the longest exposure period 120 min. The longest exposure time period relatively activates the xenobiotic detoxifying enzymes like glutathione-S-transferase, superoxide dismutase, catalase, and peroxidase enzymes. The longest duration of UV-A radiation may cooperate with pesticide detoxification mechanism in insects, making them more susceptible to insecticides. Our results demonstrated that UV irradiation causes oxidative stress, affects the activity of antioxidant enzymes, and disturbs the physiology of M. separata adults.

Insecticidal potency of RNAi-based catalase knockdown in Rhynchophorus ferrugineus (Oliver) (Coleoptera: Curculionidae)

BACKGROUND

Palm trees around the world are prone to notorious Rhynchophorus ferrugineus, which causes heavy losses of palm plantations. In Middle Eastern countries, this pest is a major threat to date palm orchards. Conventional pest control measures with the major share of synthetic insecticides have resulted in insect resistance and environmental issues. Therefore, in order to explore better alternatives, the RNAi approach was employed to knock down the catalase gene in fifth and tenth larval instars with different dsRNA application methods, and their insecticidal potency was studied.

RESULTS

dsRNA of 444 bp was prepared to knock down catalase in R. ferrugineus. Out of the three dsRNA application methods, dsRNA injection into larvae was the most effective, followed by dsRNA application by artificial feeding. Both methods resulted in significant catalase knockdown in various tissues, especially the midgut. As a result, the highest growth inhibition of 123.49 and 103.47% and larval mortality of 80 and 40% were observed in fifth-instar larvae, whereas larval growth inhibition remained at 86.83 and 69.08% with larval mortality at 30 and 10% in tenth-instar larvae after dsRNA injection and artificial diet treatment. The topical application method was the least efficient, with the lowest larval growth inhibition of 57.23 and 45.61% and 0% mortality in fifth- and tenth-instar larvae. Generally, better results were noted at the high dsRNA dose of 5 µL.

CONCLUSION

Catalase enzyme is found in most insect body tissues, and thus its dsRNA can cause broad-scale gene knockdown within the insect body, depending upon the application method. Significant larval mortality and growth inhibition after catalase knockdown in R. ferrugineus confirms its insecticidal potency and suggests a bright future for RNAi-based bioinsecticides in pest control. © 2016 Society of Chemical Industry.

Effects of nickel exposure on testicular function, oxidative stress, and male reproductive dysfunction in Spodoptera litura Fabricius

Nickel is an environmental pollutant that adversely affects the male reproductive system. In the present study, the effects of nickel exposure on Spodoptera litura Fabricius were investigated by feeding larvae artificial diets containing different doses of nickel for three generations. Damage to testes and effects on male reproduction were examined. The amount of nickel that accumulated in the testes of newly emerged males increased as the nickel dose in the diet increased during a single generation. Nickel exposure increased the amount of thiobarbituric acid reactive substances and decreased the amount of glutathione in treatment groups compared with the control. The activity levels of the antioxidant response indices superoxide dismutases, catalase, and glutathione peroxidase in the testes showed variable dose-dependent relationships with nickel doses and duration of exposure. Nickel doses also disrupted the development of the testes by decreasing the weight and volume of testes and the number of eupyrene and apyrene sperm bundles in treatment groups compared with the control. When the nickel-treated males mated with normal females, fecundity was inhibited by the higher nickel doses in all three generations, but fecundity significantly increased during the second generation, which received 5 mg kg(-1) nickel. Hatching rates in all treatments significantly decreased in a dose-dependent manner in the three successive generations. The effects of nickel on these parameters correlated with the duration of nickel exposure. Results indicate assays of testes may be a novel and efficient means of evaluating the effects of heavy metals on phytophagous insects in an agricultural environment.

Effect of Copper on Growth, Digestive and Antioxidant Enzyme Activities of Juvenile Qihe Crucian Carp, Carassius carassius, During Exposure and Recovery

The toxicity of copper (Cu) on growth and activities of digestive and antioxidant enzymes in the hepatopancreas and intestine of juvenile Qihe crucian carp Carassius carassius was evaluated. The fish were exposed in different Cu solutions for 20 days, and the 0.60 mg/L group was then transferred to clean water to initiate a 20-day recovery period after Cu exposure. Results showed that all enzyme activities decreased significantly at high-concentration (0.30 and 0.60 mg/L) and long-time (20 days) Cu exposures and increased significantly at high-concentration (0.60 mg/L) and short-time Cu exposures (1 day). After the 20-day recovery period, all enzyme activities in the 0.60 mg/L group had recovered to control levels. High-concentration (0.60 mg/L) and long-time (20 days) Cu exposure markedly hindered the growth of fish, whereas the loss of fish growth can not be compensated for by a 20-day recovery period.

Effects of phenol on ovarian P450arom gene expression and aromatase activity in vivo and antioxidant metabolism in common carp Cyprinus carpio

Ovarian cyp19a mRNA expression and P450 aromatase activity were measured in vivo in common carp Cyprinus carpio exposed to phenol for 96 h. Production of reactive oxygen species (ROS) and parameters of antioxidant defense system in serum ovary and liver of this fish after long-term phenol exposure were also studied. In vivo exposure of fish to sublethal dose of phenol for 96 h caused marked attenuation of ovarian cyp19a1a gene expression and P450 aromatase activity. Production of ROS like hydrogen peroxide and hydroxyl radicals in serum, liver and ovary in fish exposed to phenol for 15 days elevated significantly from day 1 to day 7 with no further significant increase thereafter compared to their respective control values. Total superoxide dismutase (SOD) and catalase activities in serum and ovary decreased gradually and significantly from day 1 to day 4, which then increased significantly for the rest of the exposure days. Liver SOD activity seemed to be distinctly responsive to phenol. SOD activity in liver of phenol-exposed fish started to increase gradually from day 1 to 4 with no further increase thereafter. Catalase activities in all the tissues showed significant inhibition up to day 4 which then increased gradually and significantly up to day 15 of phenol exposure compared to their respective control values. From our results, it appears that sublethal dose of phenol has the endocrine disruptive potential and effect is mediated via inhibition of ovarian P450arom gene expression and aromatase activity in vivo. Sublethal dose of phenol also caused oxidative stress, and antioxidant systems are very much effective to prevent the damages caused by the generation of ROS.

Toxicological and biochemical analyses demonstrate no toxic effect of Cry1C and Cry2A to Folsomia candida

Collembolans are common soil arthropods that may be exposed to insecticidal proteins produced in genetically engineered (GE) plants by ingestion of crop residues or root exudates. In the present study, a dietary exposure assay was validated and used to assess the lethal and sublethal effects of two Bacillus thuringiensis (Bt) insecticidal proteins, Cry1C and Cry2A, on Folsomia candida. Using the insecticidal compounds potassium arsenate (PA), protease inhibitor (E-64), and Galanthus nivalis agglutinin (GNA) mixed into Baker's yeast, we show that the assay used can detect adverse effects on F. candida. Survival and development were significantly reduced when F. candida was fed a diet containing PA, E-64, and GNA at 9, 75, and 100 μg/g diet, respectively, but not when fed a diet containing 300 μg/g Cry1C or 600 μg/g Cry2A. The activities of test antioxidant-, detoxification-, and digestion-related enzymes in F. candida were unaltered by a diet containing 300 μg/g Cry1C or 600 μg/g Cry2A, but were significantly increased by a diet containing 75 μg/g E-64. The results confirm that Cry1C and Cry2A are not toxic to F. candida at concentrations that are much higher than those encountered under field conditions.

DNA damage in haemocytes and midgut gland cells of Steatoda grossa (Theridiidae) spiders exposed to food contaminated with cadmium

The aim of this study was to assess the genotoxic effects of Cd on haemocytes and midgut gland cells of web-building spiders, Steatoda grossa (Theridiidae), exposed to the metal under laboratory conditions. Analyzes were conducted on adult females and males, fed for four weeks with cadmium-contaminated Drosophila hydei flies, grown on a medium suplemented with 0.25 mM CdCl2. The comet assay, providing a quantitative measure of DNA strand breaks, was used to evaluate the DNA damage caused by the metal. Cadmium content was measured in whole spider bodies by the AAS method. Metal body burden was significantly lower in females (0.25 µgg(-1) dry weight) than in males (3.03 µgg(-1) dry weight), suggesting that females may have more effective mechanisms controlling the uptake of metal, via the digestive tract, or its elimination from the body. Irrespectively of sex, spiders fed prey contaminated with cadmium showed significantly higher values of comet parameters: tail DNA (TDNA), tail length (TL) and olive tail moment (OTM), in comparison with the control. In midgut gland cells, the level of DNA damage was higher for males than females, while in haemocytes the genotoxic effect of cadmium was greater in females. The obtained results indicate that in spiders cadmium displays strong genotoxic effects and may cause DNA damage even at low concentrations, however the severity of damage seems to be sex- and internal organ-dependent. The comet assay can be considered a sensitive tool for measuring the deleterious effect of cadmium on DNA integrity in spiders.

Influence of catalase gene silencing on the survivability of Sitobion avenae

Reactive oxygen species (ROS), such as superoxide anions and hydrogen peroxide produced in cell metabolism, result in the disruption of cellular function and structure. Catalase (CAT), an enzyme which exists in almost all organisms including plants, invertebrates and vertebrates, acts in scavenging ROS. In this study, a sequence fragment encoding a CAT-like protein from wheat aphids ( Sitobion avenae) was cloned. Amino acid sequence alignment showed this CAT shared relatively high conservation with CAT sequences from other insects. We detected cat mRNA levels at nymphs of different stages and adults and results showed that cat expression in adults was significantly higher compared to juvenile stages. At the third instar stage, ingestion of dsCAT significantly knocked down CAT expression. Continuous feeding of dsCAT mixed in an artificial diet led to reduced survival rate and ecdysis index. This study indicates that cat, a potential target gene for management of insect pests, is important for maintaining the survival of  S. avenae.

The effects of cadmium or zinc multigenerational exposure on metal tolerance of Spodoptera exigua (Lepidoptera: Noctuidae)

The effects of ten generational zinc or cadmium pre-exposure on metal tolerance among beet armyworm Spodoptera exigua individuals were compared. These effects were assessed in animals from the 11th generation, reared on a diet either uncontaminated or contaminated with metal (cadmium or zinc). The survival rate of larvae and the degree of metal accumulation (in larvae, pupae and moths; among larval organs: gut and fat body) were analysed. Catalase, superoxide dismutase and glutathione transferase activity in larval organs of individuals subjected to different metal treatments were also measured. Animals transferred from control rearing to metals (cadmium or zinc) in the 11th generation, as well as those from multigenerational zinc treatment, but not from multigenerational cadmium treatment, had a significantly lower survival rate than control animals. Insects from the groups with the high metal treatment had high bioaccumulation factors (above 3.7 and 2.3 following cadmium and zinc, respectively). Cadmium (but not zinc) pre-exposure had a significant effect on metal accumulation in larvae. Multigenerational metal pre-exposure seemed to have mainly a negative effect on glutathione transferase activity in the gut of larvae from the 11th generation, in the case of the individuals exposed to metal other than that used in pre-exposure treatment or kept in control conditions. However, in the case of zinc pre-exposure, such effect was only apparent when zinc was replaced by cadmium. The long-term effect of cadmium on catalase activity in larvae was found.

Copper resistance selection and activity changes of antioxidases in the flesh fly Boettcherisca peregrina

Natural populations of Boettcherisca (Sarcophaga) peregrina Robineau-Desvoidy (Diptera: Sarcophagidae) were maintained for 20 generations and reared either on unpolluted diet or on polluted diet containing copper at a median lethal concentration (LC50) determined every five generations. This resulted in two reliable strains: the relative susceptible strain (S) and the copperresistant strain (R). The metal accumulation, growth and development, reproduction, and antioxidant enzymes were analyzed in the two strains. The results showed that compared with the S strain, the R strain showed increased metal accumulation and fecundity of female adults. Regardless of whether larvae were fed on diet with or without Cu(2+), the R strain showed higher activity of superoxide dismutase and glutathione S-transferase than the S strain, although without statistical significance. Moreover, the activity of superoxide dismutase and glutathione S-transferase increased when B. peregrina larvae were exposed to Cu(2+) at 100 µg/g but decreased when they were exposed to Cu(2+) at 800 µg/g. Larval catalase activity in the R strain was higher than in the S strain when larvae were fed on diet with or without Cu(2+), although these differences were significant only at the 100 µg/g concentration. Moreover, the activity of catalase decreased when larvae were exposed to experimental Cu(2+). Beyond all expectations, larval glutathione reductase activity was not significantly different between the two strains but changed slightly when larvae were exposed to experimental Cu(2+). These results indicate that copper resistance in B. peregrina larvae is mediated by superoxide dismutase, catalase, and glutathione S-transferase. These results also help in establishing a physiological link between antioxidase activity and the resistance level of B. peregrina to copper.

Gain of long tonic immobility behavioral trait causes the red flour beetle to reduce anti-stress capacity

Tonic immobility (death-feigning) behavior of the red flour beetle, Tribolium castaneum, is a predator defense mechanism; it is a reflex elicited when a beetle is jarred with the substrate, often a result of the activities of a predator. We previously demonstrated that the frequency of predation by a jumping spider, Hasarius adansoni, was significantly lower among beetles with higher frequencies and longer durations of tonic immobility (L-type) than those with lower frequencies and shorter durations of tonic immobility (S-type). However, we found that the population of L-type beetles is much smaller than that of S-type beetles in their natural habitat. Here we demonstrated that L-type beetles are significantly more sensitive to environmental stressors such as mechanical vibration and high or low temperatures. We measured expression levels of stress-responsive genes such as heat shock proteins (Hsps) and antioxidant enzymes in both types of beetles. Among the genes we investigated, only catalase gene expression levels were significantly higher in S-type than in L-type beetles. Furthermore, a similar difference in the gene expression was observed in the T. castaneum ortholog of the insect cytokine growth-blocking peptide (GBP) gene. These results indicate the possibility that high expression of catalase and GBP in S-type beetles contributes to augmentation of their anti-stress capacity and expansion of their population in their natural habitat.

The negative effects of cadmium on Bermuda grass growth might be offset by submergence

Revegetation in the water-level-fluctuation zone (WLFZ) could stabilize riverbanks, maintain local biodiversity, and improve reservoir water quality in the Three Gorges Reservoir Region (TGRR). However, submergence and cadmium (Cd) may seriously affect the survival of transplantations. Bermuda grass (Cynodon dactylon) is a stoloniferous and rhizomatous prostrate weed displaying high growth rate. A previous study has demonstrated that Bermuda grass can tolerate deep submergence and Cd stress, respectively. In the present study, we further analyzed physiological responses of Bermuda grass induced by Cd-and-submergence stress. The ultimate goal was to explore the possibility of using Bermuda grass for revegetation in the WLFZ of China's TGRR and other riparian areas. The Cd-and-submergence-treated plants had higher malondialdehyde contents and peroxidase than control, and both increased with the Cd concentration increase. All treated plants catalase activity increased with the experimental duration increases, and their superoxide dismutase also gradually increased with the Cd concentration from 1 day to 15 days. Total biomass of the same Cd-and-submergence plants increased along the experimental duration as well. Plants exposed to Cd-and-submergence stress showed shoot elongation. The heights of all treated plants were taller than those of the control. Leaf chlorophyll contents, maximum leaf length, and soluble sugars contents of all the Cd-and-submergence-treated plants were more than those of the untreated control. Although Cd inhibits plants growth, decreases chlorophyll and biomass content, and with the submergence induced the leaf and shoot elongation, more part of the Cd-and-submergence stress plants appeared in the air, exhibited fast growth with maintenance of leaf color, which guaranteed the plants' photosynthesis, and ensured the total biomass and carbohydrate sustainability, further promoting Cd-and-submergence tolerance. The results imply that the negative effects of cadmium on Bermuda grass growth might be offset by submergence.

RNAi-mediated knockdown of catalase causes cell cycle arrest in SL-1 cells and results in low survival rate of Spodoptera litura (Fabricius)

Deregulated reactive oxygen species (ROS) production can lead to the disruption of structural and functional integrity of cells as a consequence of reactive interaction between ROS and various biological components. Catalase (CAT) is a common enzyme existing in nearly all organisms exposed to oxygen, which decomposes harmful hydrogen peroxide, into water and oxygen. In this study, the full length sequence that encodes CAT-like protein from Spodoptera litura named siltCAT (GenBank accession number: JQ_663444) was cloned and characterized. Amino acid sequence alignment showed siltCAT shared relatively high conservation with other insect, especially the conserved residues which defined heme and NADPH orientation. Expression pattern analysis showed that siltCAT mRNA was mainly expressed in the fat body, midgut, cuticle and malpighian tube, and as well as over last instar larvae, pupa and adult stages. RNA interference was used to silence CAT gene in SL-1 cells and the fourth-instar stage of S. litura larvae respectively. Our results provided evidence that CAT knockdown induced ROS generation, cell cycle arrest and apoptosis in SL-1 cells. It also confirmed the decrease in survival rate because of increased ROS production in experimental groups injected with double-stranded RNA of CAT (dsCAT). This study implied that ROS scavenging by CAT is important for S. litura survival.

The molecular characterization of antioxidant enzyme genes in Helicoverpa armigera adults and their involvement in response to ultraviolet-A stress

Ultraviolet (UV) radiation can cause oxidative stress in insects. To gain insight into the roles of different antioxidant enzymes of Helicoverpa armigera adults in response to oxidative stress caused by UV-A at a molecular level, three antioxidant enzyme genes [encoding copper zinc superoxide dismutase (Cu/ZnSOD), catalase (CAT) and glutathione peroxidase (GPX)] were cloned. The deduced amino acid sequences of these genes are similar to that of other insects. In addition, the expression profiles of genes from a classic antioxidant defense system, comprising Cu/ZnSOD, manganese superoxide dismutase (MnSOD), CAT, thioredoxin peroxidase, GPX and glutathione-S-transferase, were also determined. The results indicated that all antioxidant enzyme genes (except MnSOD in females) were significantly upregulated at certain time points (from 30 to 90min) in both male and female adults of H. armigera following UV-A radiation. We also found that longer periods of radiation exposure did not yield higher levels of mRNA expression. Furthermore, changes of determined physiological parameters (glutathione, Cu/ZnSOD and MnSOD activity) were basically consistent with the gene expression profiles. We therefore infer that the different antioxidant enzymes of H. armigera act in a coordinated manner at the transcriptional level against oxidative stress caused by UV-A radiation.

The localisation of HSP70 and oxidative stress indices in heads of Spodoptera exigua larvae in a cadmium-exposed population

The effects of cadmium toxicity may vary between animals with different history of metal exposure. The aim of our study was to examine HSP70, protein carbonyl levels, catalase activity and total antioxidant capacity in the heads of Spodoptera exigua (Hübner) larvae originated from undergoing 1- and 44-generational cadmium treatment and in control (those that were not exposed to cadmium). We also measured the cadmium concentration and DNA damage level in the larvae. We observed higher level of heat shock proteins (HSPs) in the heads of larvae derived from multi-generational metal treatment than in the heads of those from one-generational treatment (derived from the control rearing). Analysis of HSP localisation in the larval brain suggests that these changes could be important for protecting the neural function of larval mushroom bodies for animals selected during multigenerational metal exposure. Animals from one-generational treatment had, in turn, higher total antioxidant capacity than animals from multigenerational treatment. Anyway, animals from one- and 44-generational metal treatments did not differ in metal accumulation in the heads and the whole larval bodies, catalase activity or DNA damage level. All these measurements were higher than for control larvae and cadmium accumulation in the heads was much lower than in the whole bodies.

Cd and Pb contents in soil, plants, and grasshoppers along a pollution gradient in Huludao City, Northeast China

Cd and Pb contents in soil, plants, and two grasshopper species (Locusta migratoria manilensis and Acrida chinensis) were examined to quantify the influence ranges of zinc smelting on heavy metal contamination. Samples were collected simultaneously from Huludao City, a chemical and nonferrous smelting base in Northeast China. Cd and Pb contamination in soil and plants were serious. Cd and Pb contents were 13.32 and 8.83 mg/kg in L. migratoria manilensis and 16.67 and 15.00 mg/kg in A. chinensis, respectively. Correlation analysis indicated the same metal source for Cd and Pb in soil, plants, and grasshoppers. Cd and Pb contents in soil, plants, and grasshoppers were all significantly related to distances far from the zinc smelter in good negative logarithm model. The fitting curves indicated that the influence radius of the smelter on heavy metal contamination was about 4,000 m for soil and plants and about 2,000 m for grasshoppers.

Molecular toxicity of earthworms induced by cadmium contaminated soil and biomarkers screening

Earthworms (Eisenia fetida) were used to study the impact of low-dose cadmium in treated artificial soil (0, 0.6, 3, 6, 15, 30 mg/kg) and contaminated natural soil (1.46 mg/kg). The changes of earthworms' physiological related gene expressions of metallothionein (MT), annetocin, calreticulin and antimicrobial peptides were detected using real-time PCR after a 70-day incubation period. The results showed that low doses of cadmium could up regulate earthworms' MT and down regulate annetocin gene expression and show a significant positive and negative correlation respectively. The expression of two other genes, calreticulin and anti-microbial peptides, was induced at low doses of cadmium (highest gene expression at 0.6 mg/kg for calreticulin and 6 mg/kg for anti-microbial peptides) and inhibited at high doses. No significant correlation was found for these two genes. This study shows that MT and annetocin genes expression found in earthworms in contaminated soil have the potential to be developed as biomarkers of soil cadmium pollution.

Decrease in catalase activity of Folsomia candida fed a Bt rice diet

Here we report the effects of three Bt-rice varieties and their non-Bt conventional isolines on biological traits including survival, reproduction, and the activities of three antioxidant enzymes superoxide dismutase, catalase and peroxidase, in the Collembolan, Folsomia candida. The reproduction was significantly lower when fed Kemingdao and Huahui1 than those feeding on their non-GM near-isogenic varieties Xiushui and Minghui63 respectively, this can be explained by the differences of plant compositions depended on variety of rice. The catalase activity of F. candida was significantly lower when fed the Bt-rice variety Kemingdao compared to the near-isogenic non-Bt-rice variety Xiushui. This suggests that some Bt-rice varieties may impose environmental stress to collembolans. We emphasize that changes in activity of antioxidant enzymes of non-target organisms are important in understanding the ecological consequences for organisms inhabiting transgenic Bt-rice plantations.

Oxidative stress in newly-hatched Chorthippus brunneus--the effects of zinc treatment during diapause, depending on the female's age and its origins

The responses of glutathione, glutathione S-transferases (GSTs), and catalase (CAT) were determined in 1-day-old larvae of Chorthippus brunneus Thunberg, 1815, a grasshopper exposed to zinc during diapause, from unpolluted (Pilica) or polluted (Olkusz, Szopienice) sites. The aim of the work was to search for differences among populations of the insects as a result of various multistress pressures in their habitats. The question of zinc toxicity in the context of energy allocation was also considered. Zinc caused a decrease in glutathione concentration in the body of zinc-treated larvae. Significant differences between control and zinc-treated groups were confirmed for young females' progeny from Pilica and Olkusz as well as old females' progeny from Olkusz. GSTs activity was generally not influenced by zinc. It is possible that GSTs were not the most important target of zinc action. On the contrary, the influence of zinc on CAT activity was found. The increase in CAT activity after zinc treatment was similar for all studied populations. An increase in CAT activity after zinc exposure seems to be the most universal reaction. CAT activity in zinc-treated grasshoppers may explain the mechanism of zinc toxicity based on reactive oxygen forms generation.

Chronic accumulation of cadmium and its effects on antioxidant enzymes and malondialdehyde in Oxya chinensis (Orthoptera: Acridoidea)

The accumulation of cadmium (Cd) and its effects on antioxidant enzyme activities and malondialdehyde (MDA) levels of Chinese rice grasshopper (Oxya chinensis) were evaluated under the laboratory conditions. Our results showed that Cd accumulation in O. chinensis exhibited a concentration-dependent increase in both males and females under Cd pollution. Environmental Cd can lead to the absorption of large quantities of Cd, which induces oxidative damage in insects by altering antioxidant defense enzyme systems. Our results demonstrated that Cd stress caused a significant decrease in glutathione peroxidase (GPx) levels and a significant increase in superoxide (SOD) dismutase and catalase (CAT) activities. In the grasshoppers, the MDA content was also enhanced, with an increase in Cd concentrations and a positive correlation between them; for females from second instar nymphs to the adult stage, R(2) was 0.6467, 0.9136, 0.6516, 0.942 and 0.7182, whereas for males, it was 0.6467, 0.8239, 0.9302, 0.7861, 0.8632, respectively. We also observed differences in the effects of Cd between grasshoppers of different developmental stages and genders, which suggested that the insect's developmental stage and sex should be considered when studying enzyme activity.

Effects of cadmium exposure on lipid peroxidation and the antioxidant system in fourth-instar larvae of Propsilocerus akamusi (Diptera: Chironomidae) under laboratory conditions

Enzymatic antioxidants such as selenium-dependent glutathione peroxidase (GPx), glutathione transferase (GST), glutathione reductase (GR), and superoxide dismutases (SOD), as well as the concentration of hydrogen peroxide (H2O2) and malondialdehyde (MDA, an indicator of lipid peroxidation) were determined to identify which antioxidant enzymes participate in the efficient scavenging of ROS generated upon exposure to high doses of Cd2+ in fourth-instar Propsilocerus akamusi (Tokuna) (Diptera: Chironomidae) larvae after 72-h exposure. A significant increase in MDA levels and a change in GR and GPx activities in the Cd(2+)-treated P. akamusi were observed. The MDA in 25.0 and 50.0 mmol/liter treatments was significantly higher than that of the control dose after 72 h exposure. GPx activity was significantly induced by Cd2+ exposure only in the 50.0-mmol/liter treatment with a 0.59-fold increase in the control. All doses of Cd2+ significantly suppressed GR activity compared with the findings for the control dose, with an inhibited rate up to 0.55-fold in the 25.0 mmol/liter Cd2+ treatment. SOD and GST activities were not altered. The results indicate that Cd2+ can induce oxidative stress as indicated by the changes in lipid peroxidation and antioxidant status. For P. akamusi, an increase in the dose that the threshold needed for defense (namely, MDA level and GPx activity) activation was achieved. From this, organisms can be hypothesized to enable cells to avoid oxidant stress up to a certain extent where damage is again measurable (higher Cd2+ concentration).