Transcriptome-Wide Identification of Differentially Expressed Genes in Chinese Oak Silkworm Antheraea pernyi in Response to Lead Challenge

Transcriptome Profiling Unveils the Mechanisms of Inflammation, Apoptosis, and Fibrosis in the Liver of Juvenile Largemouth Bass Micropterus salmoides Fed High-Starch Diets

The aim of this study was to explain the mechanism underlying the liver injury of juvenile largemouth bass Micropterus salmoides in response to high-starch diet intake. Three diets were formulated with different starch levels, being abbreviated as treatment LS (low starch, 8.13% starch), MS (medium starch, 14.1% starch), and HS (high starch, 20.1% starch), respectively. Fish were fed with their respective diets to apparent satiation for 56 days. The results showed that growth retardation of the HS fish was associated with the reduction in feed intake rather than feed utilization. Histological evaluation of the livers showed that vacuolization was the most prevalent characteristic in the MS fish, while ballooning degeneration, apoptosis, fibrosis, and inflammation were observed in the HS fish. Transcriptome profiling suggested that liver inflammation was mediated by Tlr signal transduction, which activated the Pi3k/Akt/Nfκb signaling axis to promote the release of proinflammatory factors including Il-8 and Ip-10. Hepatocyte apoptosis was mediated by the extrinsic pathway through death receptors including Fas and Tnfr, which coordinately activated the Fadd/caspase-8 death signaling axis. An autonomous inhibition program was identified to counteract the apoptosis signal, and the PI3K/Akt signaling pathway might play an important role in this process through regulating the expression of iap and diablo. Liver fibrosis was mediated through the Tgf-β and Hh signaling pathways. Upon secretion, Tgf-β1/3 bound to TgfβrI/II complex on the liver cell membrane, which induced the phosphorylation of downstream Smad2/3. When Hh interacted with the membrane receptor Ptc, Smo was activated to initiate signaling, driving the activation of Gli. The activation of both Smad2/3 and Gli promoted their nuclear translocation thereby regulating the transcription of target genes, which resulted in the activation and proliferation of HSCs. The activated HSCs constantly expressed colla1 and ctgf, which facilitated substantial accumulation of ECM. It should be noted that the molecular mechanism of liver injury in this study was speculated from the transcriptome data thus further experimental verification is warranted for this speculation.

Walnut protein isolate-epigallocatechin gallate nanoparticles: A functional carrier enhanced stability and antioxidant activity of lycopene

Walnut isolate protein (WPI)-epigallocatechin gallate (EGCG) conjugates can be employed to creat food-grade delivery systems for preserving bioactive compounds. In this study, WPI-EGCG nanoparticles (WENPs) were developed for encapsulating lycopene (LYC) using the ultrasound-assisted method. The results indicated successful loading of LYC into these WENPs, forming the WENPs/LYC (cylinder with 200-300 nm in length and 14.81-30.05 nm in diameter). Encapsulating LYC in WENPs led to a notable decrease in release rate and improved stability in terms of thermal, ultraviolet (UV), and storage conditions compared to free LYC. Simultaneously, WENPs/LYC exhibited a synergistic and significantly higher antioxidant activity with an EC50 value of 23.98 μg/mL in HepG2 cells compared to free LYC's 31.54 μg/mL. Treatment with WENPs/LYC led to a dose-dependent restoration of intracellular antioxidant enzyme activities (SOD, CAT, and GSH-Px) and inhibition of intracellular malondialdehyde (MDA) formation. Furthermore, transcriptome analysis indicated that enrichment in glutathione metabolism and peroxisome processes following WENPs/LYC addition. Quantitative real-time reverse transcription PCR (qRT-PCR) verified the expression levels of related genes involved in the antioxidant resistance pathway of WENPs/LYC on AAPH-induced oxidative stress. This study offers novel perspectives into the antioxidant resistance pathway of WENPs/LYC, holding significant potential in food industry.

Effect of acute exposure of Hg on physiological parameters and transcriptome expression in silkworms (Bombyx mori)

Mercury (Hg) contamination poses a global threat to the environment, given its elevated ecotoxicity. Herein, we employed the lepidopteran model insect, silkworm (Bombyx mori), to systematically investigate the toxic effects of Hg-stress across its growth and development, histomorphology, antioxidant enzyme activities, and transcriptome responses. High doses of Hg exposure induced evident poisoning symptoms, markedly impeding the growth of silkworm larvae and escalating mortality in a dose-dependent manner. Under Hg exposure, the histomorphology of both the midgut and fat body exhibited impairments. Carboxylesterase (CarE) activity was increased in both midgut and fat body tissues responding to Hg treatment. Conversely, glutathione S-transferase (GST) levels increased in the fat body but decreased in the midgut. The transcriptomic analysis revealed that the response induced by Hg stress involved multiple metabolism processes. Significantly differently expressed genes (DEGs) exhibited strong associations with oxidative phosphorylation, nutrient metabolisms, insect hormone biosynthesis, lysosome, ribosome biogenesis in eukaryotes, and ribosome pathways in the midgut or the fat body. The findings implied that exposure to Hg might induce the oxidative stress response, attempting to compensate for impaired metabolism. Concurrently, disruptions in nutrient metabolism and insect hormone activity might hinder growth and development, leading to immune dysfunction in silkworms. These insights significantly advance our theoretical understanding of the potential mechanisms underlying Hg toxicity in invertebrate organisms.

Effects of Chromium Exposure on the Gene Expression of the Midgut in Silkworms, Bombyx mori

Chromium is a severe heavy metal pollutant with significant environmental risks. The effects of Chromium on the digestion of Bombyx mori (silkworms) are of particular importance due to their ecological and economic significance. Herein, RNA sequencing was conducted on nine midgut samples from silkworms exposed to control, 12 g/kg and 24 g/kg Chromium chemical diets. Comparative transcriptomics revealed that under moderate Chromium exposure, there was a significant increase in up-regulated genes (1268 up-regulated to 857 down-regulated), indicating a stimulation response. At higher stress levels, a weakened survival response was observed, with a decrease in up-regulated genes and an increase in down-regulated genes (374 up-regulated to 399 down-regulated). A notable shift in cellular responses under medium chromium exposure was exposed, signifying the activation of crucial metabolic and transport systems and an elevation in cellular stress and toxicity mechanisms. The observation of up-regulated gene expression within xenobiotic metabolism pathways suggests a heightened defense against Chromium-induced oxidative stress, which was primarily through the involvement of antioxidant enzymes. Conversely, high-dose Chromium exposure down-regulates the folate biosynthesis pathway, indicating biological toxicity. Two novel genes responsive to pressure were identified, which could facilitate future stress adaptation understanding. The findings provide insights into the molecular mechanisms underlying silkworms' digestion response to Chromium exposure and could inform its biological toxicity.

Genome-Wide Identification of Detoxification Genes in Wild Silkworm Antheraea pernyi and Transcriptional Response to Coumaphos

For a half-century, the commercial wild silkworm, Antheraea pernyi, has been protected by coumaphos, which is an internal organophosphorus insecticide used to kill the potential parasitic fly larvae inside. Knowledge about the detoxification genes of A. pernyi as well as the detoxification mechanism for this species remains severely limited. In this study, we identified 281 detoxification genes (32 GSTs, 48 ABCs, 104 CYPs, and 97 COEs) in the genome of this insect, which are unevenly distributed over 46 chromosomes. When compared to the domesticated silkworm, Bombyx mori, a lepidopteran model species, A. pernyi has a similar number of ABCs, but a greater number of GSTs, CYPs, and COEs. By transcriptome-based expression analysis, we found that coumaphos at a safe concentration level significantly changed the pathways related to ATPase complex function and the transporter complex in A. pernyi. KEGG functional enrichment analysis indicated that protein processing in the endoplasmic reticulum was the most affected pathway after coumaphos treatment. Finally, we identified four significantly up-regulated detoxification genes (ABCB1, ABCB3, ABCG11, and ae43) and one significantly down-regulated detoxification gene (CYP6AE9) in response to coumaphos treatment, suggesting that these five genes may contribute to detoxification of coumaphos in A. pernyi. Our study provides the first set of detoxification genes for wild silkworms from Saturniidae and highlights the importance of detoxification gene repertoire in insect pesticide tolerance.

Transcriptome analysis provides insights into the molecular mechanism of liver inflammation and apoptosis in juvenile largemouth bass Micropterus salmoides fed low protein high starch diets

The present study was conducted to investigate the regulatory mechanism of liver injury in largemouth bass Micropterus salmoides (LMB) fed low protein high starch diets. Two isolipidic and isoenergetic diets were formulated with different protein and starch ratios, being named as diets P49S9 (48.8 % protein and 9.06 % starch) and P42S18 (42.4 % protein and 18.2 % starch). Each diet was fed to triplicate replicates of LMB (initial body weight, 4.65 ± 0.01 g) juveniles. Fish were fed to visual satiation for 8 weeks. The results indicated that though the P42S18 fish up-regulated the feeding ratio to meet their protein requirements, feeding efficiency ratio and growth performance were impaired in treatment P42S18 as compared to treatment P49S9. Periodic acid-Schiff (PAS) staining showed glycogen accumulated in the liver of LMB fed low protein high starch diets, and the reason should be attributed to down-regulated expression of the glycogenolytic glycogen debranching enzyme. Lower liver lipid level was associated with feeding low protein high starch diets in LMB, which should be resulted from the changes in hepatic glycerolipid metabolism regulated by lipoprotein lipase (representative of triglyceride synthesis, up-regulated) and diacylglycerol acyltransferase (representative of triglyceride breakdown, down-regulated). Though fasting plasma glucose level was comparable, treatment P42S18 performed inferior glucose tolerance to treatment P49S9. Hematoxylin-eosin (HE) and TdT-mediated dUTP Nick-End Labeling (TUNEL) staining suggested that feeding low protein high starch diets induced disruption of structural integrity, inflammation and apoptosis in the hepatocytes of LMB. As expected, KEGG pathways analysis indicated that many of the up-regulated differentially expressed genes were enriched in AGE (advanced glycation end product)/RAGE (receptor for AGE), Toll-like receptor and apoptosis signaling pathways. Our transcriptome data revealed that feeding low protein high starch diets might promote the accumulation of AGEs in LMB, which bound to RAGE and subsequently induced PI3K/Akt signal pathway. The activation of Akt induced NF-κB translocation into the nucleus thus releasing proinflammatory factors including tumor necrosis factor-α (TNF-α) and interleukin-8. The release of these inflammatory factors concomitantly induced T cell stimulation and natural killer cells chemotactic effects through Toll-like receptor signaling pathway. Besides mediating inflammation and immune response, TNF-α signal transduction participated in mediating apoptosis through the receptor of TNF (TNF-R1) pathway by up-regulating the expression of caspase 8 and cytochrome c. In conclusion, our results demonstrated that feeding low protein and high starch diets induced hepatocytes inflammation and apoptosis in LMB through the PI3K/Akt/NF-κB signaling pathway.

Cadmium/lead tolerance of six Dianthus species and detoxification mechanism in Dianthus spiculifolius

Toxic heavy metal contaminants seriously affect plant growth and human health. Reducing the accumulation of toxic metals by phytoremediation is an effective way to solve this environmental problem. Dianthus spiculifolius Schur is an ornamental plant with strong cold and drought tolerance. Because of its fast growth, well-developed root system, and large accumulation of biomass, D. spiculifolius has potential applications as a heavy metal hyperaccumulator. Therefore, the aim of this study was evaluate the ability of D. spiculifolius and other Dianthus species to remediate heavy metals, with an ultimate goal to identify available genetic resources for toxic metal removal. The cadmium (Cd) and lead (Pb) tolerance and accumulation of six Dianthus species were analyzed comparatively in physiological and biochemical experiments. Compared with the other Dianthus species, D. spiculifolius showed higher tolerance to, and greater accumulation of, Cd and Pb. Second-generation transcriptome analysis indicated that glutathione transferase activity was increased and the glutathione metabolism pathway was enriched with genes encoding antioxidant enzymes (DsGST, DsGST3, DsGSTU10, DsGGCT2-1, and DsIDH-2) that were up-regulated under Cd/Pb treatment by RT-qPCR in D. spiculifolius. When expressed in yeast, DsGST, DsGST3, DsGSTU10 and DsIDH-2 enhanced Cd or Pb tolerance. These results indicate that D. spiculifolius has potential applications as a new ornamental hyperaccumulator plant, and that antioxidant enzymes might be involved in regulating Cd/Pb accumulation and detoxification. The findings of this study reveal some novel genetic resources that can be used to breed new plant varieties that tolerate and accumulate heavy metals.

Wound-Healing Effect of Antheraea pernyi Epidermal Growth Factor

To evaluate the wound-healing effect of Antheraea pernyi epidermal growth factor (ApEGF), we performed the sequence analysis, cloning, and prokaryotic expression of cDNA from the ApEGF gene, examined the transcriptional changes, and investigated the wound-healing effect of this protein in cells and rat epidermis. Primers were designed based on available sequence information related to the ApEGF gene in a public database, and part of the ApEGF sequence was obtained. The full-length cDNA sequence of ApEGF was obtained using inverse PCR. The gene sequence fragment of ApEGF was 666 bp in length, encoding 221 amino acids, with a predicted protein mass of 24.19 kD, an isoelectric point of 5.15, and no signal peptide sequence. Sequence homology analysis revealed 86.1% sequence homology with Bombyx mori, 92.7% with Manducal sexta, 92.6% with Trichoplusia ni, and 91.8% with Helicoverpa armigera. ApEGF was truncated and then subjected to prokaryotic expression, isolation, and purification. Truncated ApEGF was used for wound-healing experiments in vitro and in vivo. The results showed that after 48 h, transforming growth factor (TGF)-β1 had 187.32% cell growth effects, and the ApEGF group had 211.15% cell growth compared to the control group in vitro. In rat epidermis, truncated ApEGF showed a significantly better healing effect than the control. This result indicated that ApEGF, which exerted a direct wound-healing effect, could be used in wound-healing therapy.

Larval crowding effects during early development in the Chinese oak silkmoth Antheraea pernyi (Lepidoptera: Saturniidae)

Chinese sericulture relies in part on the rearing of the Chinese oak silkmoth Antheraea pernyi, an insect with key cultural and ecological roles. While feeding primarily on oak, Antheraea species are known to accept alternative hosts such as birch Betula sp with little to no apparent negative fitness consequences. This opens up the range of hostplants that could be used for large-scale rearing of A. pernyi for silk production and food, or used by this species in possible invasions. To date, however, the natural history and ecology of A. pernyi remain subject of investigation. For instance, we still do not know how individuals respond to crowding developmental environments, which is an important factor to consider for the ecology of the species as well as for commercial rearing. Here, I describe the implications of larval crowding to the survival and growth of A. pernyi larvae during early development. I show that higher crowding is associated with stronger negative effects on growth and survival, corroborating findings from other holometabolous insects. I then discuss the implications of this findings for our understanding of optimum larval crowding. Overall, the findings reveal important ecological information for an insect species key for provisioning and cultural ecosystem services.

The gut commensal bacterium Enterococcus faecalis LX10 contributes to defending against Nosema bombycis infection in Bombyx mori

BACKGROUND

Microsporidia, a group of obligate intracellular fungal-related parasites, have been used as efficient biocontrol agents for agriculture and forestry pests due to their host specificity and transovarial transmission. They mainly infect insect pests through the intestinal tract, but the interactions between microsporidia and the gut microbiota of the host have not been well demonstrated.

RESULTS

Based on the microsporidia-Bombyx mori model, we report that the susceptibility of silkworms to exposure to the microsporidium Nosema bombycis was both dose and time dependent. Comparative analyses of the silkworm gut microbiome revealed substantially increased abundance of Enterococcus belonging to Firmicutes after N. bombycis infection. Furthermore, a bacterial strain (LX10) was obtained from the gut of B. mori and identified as Enterococcus faecalis based on 16S rRNA sequence analysis. E. faecalis LX10 reduced the N. bombycis spore germination rate and the infection efficiency in vitro and in vivo, as confirmed by bioassay tests and histopathological analyses. In addition, after simultaneous oral feeding with E. faecalis LX10 and N. bombycis, gene (Akirin, Cecropin A, Mesh, Ssk, DUOX and NOS) expression, hydrogen peroxide and nitric oxide levels, and glutathione S-transferase (GST) activity showed different degrees of recovery and correction compared with those under N. bombycis infection alone. Finally, the enterococcin LX protein was identified from sterile LX10 fermentation liquid based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis.

CONCLUSION

Altogether, the results revealed that E. faecalis LX10 with anti-N. bombycis activity might play an important role in protecting silkworms from microsporidia. Removal of these specific commensal bacteria with antibiotics and utilization of transgenic symbiotic systems may effectively improve the biocontrol value of microsporidia. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Transcriptome Sequencing Highlights the Regulatory Role of DNA Methylation in Immune-Related Genes' Expression of Chinese Oak Silkworm, Antheraea pernyi

Antheraea pernyi is an important lepidopteran used as a model insect species to investigate immune responses, development, and metabolism modulation. DNA methylation has recently been found to control various physiological processes throughout the life of animals; however, DNA methylation and its effect on the physiology of insects have been poorly investigated so far. In the present study, to better understand DNA methylation and its biological role in the immune system, we analyzed transcriptome profiles of A. pernyi pupae following DNA methylation inhibitor injection and Gram-positive bacteria stimulation. We then compared the profiles with a control group. We identified a total of 55,131 unigenes from the RNA sequence data. A comparison of unigene expression profiles showed that a total of 680 were up-regulated and 631 unigenes were down-regulated in the DNA-methylation-inhibition-bacteria-infected group compared to the control group (only bacteria-injected pupae), respectively. Here, we focused on the immune-related differentially expressed genes (DEGs) and screened 10 genes that contribute to immune responses with an up-regulation trend, suggesting that microbial pathogens evade host immunity by increasing DNA methylation of the host genome. Furthermore, several other unigenes related to other pathways were also changed, as shown in the KEGG analysis. Taken together, our data revealed that DNA methylation seems to play a crucial biological role in the regulation of gene expression in insects, and that infection may enhance the host genome DNA methylation by a yet-unknown mechanism.

Cd exposure-triggered metabolic disruption increases the susceptibility of Lymantria dispar (Lepidoptera: Erebidae) larvae to Mamestra brassicae nuclear polyhedrosis virus: A multi-omics study

Biological control is an environmentally friendly and effective pest control strategy, but it is often affected by a variety of abiotic factors in the pest control area. Here, the susceptibility of gypsy moth larvae to Mamestra brassicae nuclear polyhedrosis virus (MbNPV) under Cd treatment at the low and high dosages was investigated, and the mechanism of Cd stress affecting virus susceptibility of gypsy moth larvae was analyzed from a metabolic perspective by combining transcriptome and metabolome of the larval fat body. Our results showed that the mortality of MBNPV infection on gypsy moth larvae pre-exposed to Cd was significantly higher than that of larvae without Cd pre-exposure, and the joint effects of Cd exposure and virus infection on larval mortality were demonstrated to be synergistic. Transcriptome analysis revealed that amino acid and carbohydrate transport and metabolism accounted for most of the differently expressed genes in the low Cd and high Cd treatment groups. Consistent with the transcriptome results, metabolome analysis also showed that most metabolites affected by Cd exposure were involved in amino acid and carbohydrate metabolism. Function analysis showed that the contents of several amino acids (e.g. tryptophan and tyrosine) with antioxidant properties were significantly increased in Cd-treated gypsy moth larvae. Taken together, Cd exposure as an environmental factor, promotes the susceptibility of gypsy moth larvae to MbNPV, and metabolic disruption, especially amino acids and carbohydrates-related metabolism, is responsible for the increased susceptibility of gypsy moth larvae to virus under Cd stress.

Molecular response mechanisms of silkworm (Bombyx mori L.) to the toxicity of 1-octyl-3-methylimidazole chloride based on transcriptome analysis of midguts and silk glands

In a previous study, silkworm larvae were used as a novel model to assess the biotoxicity of ILs, which showed that ILs could cause significant physiological and biochemical changes in midguts and silk glands of the larvae, and result in the death of larvae. In order to investigate the toxicity of 1-octyl-3-methylimidazole chloride ([C₈mim]Cl) to the larvae at molecular level, RNA-sequencing technology was used to construct transcriptomic profiles of midguts and silk glands in this work. Results showed that a lot of differentially expressed genes (DEGs) were effectively screened out through bioinformatics software based on the transcriptome data and reference genome. To give more detail, 5118 and 2211 DEGs (926 and 822 DEGs) were obtained in the midguts (silk glands) when the larvae were exposed to [C₈mim]Cl for 6 and 12 h, respectively, relative to the controls. In addition, gene ontology (GO) analysis suggested that the DEGs could be divided into three categories (i.e., biological process, cellular component, and molecular function), and were involved in multiple organelle functions and complex biological processes. Kyoto encyclopedia of genes and genomes (KEGG) analysis showed that the DEGs were enriched in a variety of pathways, such as signal transduction, apoptosis, glycolysis, peroxisome, autophagy, hippo signaling pathway, arginine and proline metabolism. Results of quantitative real-time PCR and histopathological observation indicated that molecular mechanism of the larvae against [C₈mim]Cl toxicology may be attributed to cell apoptosis regulation via both the mitochondrial pathway and the death receptor-initiated pathway. Thus, these results provided useful data for exploring the toxicity of ILs to insects at molecular level.

Integration of transcriptome and proteome reveals molecular mechanisms underlying stress responses of the cutworm, Spodoptera litura, exposed to different levels of lead (Pb)

Heavy metals are major environmental pollutants that affect organisms across different trophic levels. Herbivorous insects play an important role in the bioaccumulation, and eventually, biomagnification of these metals. Although effects of heavy metal stress on insects have been well-studied, the molecular mechanisms underlying their effects remain poorly understood. Here, we used the RNA-Seq profiling and isobaric tags for relative and absolute quantitation (iTRAQ) approaches to unravel these mechanisms in the polyphagous pest Spodoptera litura exposed to lead (Pb) at two different concentrations (12.5 and 100 mg Pb/kg; PbL and PbH, respectively). Altogether, 1392 and 1630 differentially expressed genes (DEGs) and 58, 114 differentially expressed proteins (DEPs) were identified in larvae exposed to PbL and PbH, respectively. After exposed to PbL, the main up-regulated genes clusters and proteins in S. litura larvae were associated with their metabolic processes, including carbohydrate, protein, and lipid metabolism, but the levels of cytochrome P450 associated with the pathway of xenobiotic biodegradation and metabolism were found to be decreased. In contrast, the main up-regulated genes clusters and proteins in larvae exposed to PbH were enriched in the metabolism of xenobiotic by cytochrome P450, drug metabolism-cytochrome P450, and other drug metabolism enzymes, while the down-regulated genes and proteins were found to be closely related to the lipid (lipase) and protein (serine protease, trypsin) metabolism and growth processes (cuticular protein). These findings indicate that S. litura larvae exposed to PbL could enhance food digestion and absorption to prioritize for growth rather than detoxification, whereas S. litura larvae exposed to PbH reduced food digestion and absorption and channelized the limited energy for detoxification rather than growth. These contrasting results explain the dose-dependent effects of heavy metal stress on insect life-history traits, wherein low levels of heavy metal stress induce stimulation, while high levels of heavy metal stress cause inhibition at the transcriptome and proteome levels.

The susceptibility of Lymantria dispar larvae to Beauveria bassiana under Cd stress: A multi-omics study

Insect susceptibility to entomopathogenic microorganisms under heavy metal stress, as well as its regulatory mechanism is still poorly understood. This study aims to investigate the susceptibility of gypsy moth larvae to Beauveria bassiana under cadmium (Cd) stress (at 3.248 or 44.473 mg Cd/kg fresh food), and reveal the potential molecular mechanisms underlying the Cd effect on the larval susceptibility to B. bassiana via combined transcriptome and proteome analyses. Our results showed that pre-exposure to Cd increased the susceptibility of gypsy moth larvae to B. bassiana, and there was an additive effect between Cd exposure and B. bassiana infection on the larval mortality. Under the Cd stress at low and high concentrations, 138 and 899 differentially expressed genes (DEGs), as well as 514 and 840 differentially expressed proteins (DEPs) were identified, respectively. Immunotoxic effects induced by Cd exposure at the transcription level increased in a negative dose-response manner, with no immunity-related DEGs obtained at the low Cd concentration and a high number of immunity-related DEGs down-regulated at the high Cd concentration. In contrast, a potentially suppressed or stimulated trend in the Toll and Imd signaling pathway at protein level was revealed under low or high concentration of Cd treatment. Analysis of xenobiotics biodegradation-related pathways at both transcription and translation levels revealed that the gypsy moth larvae possessed an efficient homeostasis regulatory mechanism to the low-level Cd exposure, but exhibited a reduced xenobiotics biodegradation capability to the Cd stress at high levels. Together, these findings demonstrate Cd contamination promote the microbial-based biocontrol efficacy, and unravel the molecular regulatory network of heavy metal exposures that affects susceptibility of insects to pathogenic diseases.

Transcriptome analysis of the ovary of beet armyworm Spodoptera exigua under different exposures of cadmium stress

Heavy metal pollution is becoming an increasingly serious problem globally, and cadmium pollution ranks first in the world. Reproduction in insects is affected by cadmium stress in a dose-dependent manner. However, no previous studies have examined the molecular mechanisms underlying the influence of cadmium exposure on insect reproduction. In this study, RNA-Seq was used to investigate changes in ovary gene expression in newly emerged female beet army worms. The beet armyworms were reared under 4 cadmium concentrations: 0 mg/kg (control), low 0.2 mg/kg (L), medium 12.8 mg/kg (M) and high 51.2 mg/kg (H). Compared with the control (CK), a total of 3453 differentially expressed genes (DEGs) were identified in L cadmium stress, including 1791 up-regulated and 1662 down-regulated candidates; in L versus M groups, 982 up-regulated and 658 down-regulated DEGs; and in M versus H groups, 6508 up-regulated and 2000 down-regulated DEGs were identified and the expression patterns of ten genes were verified by q PCR. Many of the identified DEGs were relevant to juvenile hormone and molting hormone biosynthesis, insulin secretion, estrogen signaling, amino acid metabolism and lipid biosynthesis. These data will provide a molecular prospective to understand the ecological risk of heavy metal pollution and are a resource for selecting key genes as targets in gene-editing/silencing technologies for sustainable pest management.

Transcriptome analysis reveals gene expression changes of the fat body of silkworm (Bombyx mori L.) in response to selenium treatment

A comparative transcriptome analysis was conducted to investigate the gene expression changes in the fat body of silkworm after treatment with different concentrations (50 μM and 200 μM) of selenium (Se). 912 differential expression genes (DEGs) (371 up-regulated and 541 down-regulated) and 1420 DEGs (1078 up-regulated and 342 down-regulated) were identified in silkworm fat body treated with 50 μM and 200 μM of Se, respectively. In case of 50 μM group, DEGs were mainly enriched in the peroxisome pathway and fatty acid metabolism pathway, and later were associated with antioxidant defense and nutrition regulation. After 200 μM Se-treatment, DEGs were mainly located in the glycerolipid metabolism and arachidonic acid metabolism pathways, which further encoded detoxification related genes. Furthermore, 32 candidate DEGs from these pathways had been selected to confirm the RNA-seq data. Among these DEGs, 14 genes were up-regulated in the 50 μM Se-treated group (only three genes in the 200 μM Se-treated group) which were involved in lipid metabolism and antioxidant defense, and 13 up-regulated genes (only two genes were up-regulated in the 50 μM Se-treated group) were involved in detoxification of the 200 μM Se-treated group. These changes showed that lower concentration of Se could regulate the nutrition and promote antioxidation pathways; whereas, high levels of Se promoted the detoxification of silkworm. These findings can be helpful to understand the possible mechanisms of Se action and detoxification in silkworm and other insects.

Transcriptome-wide identification of differentially expressed genes in Procambarus clarkii in response to chromium challenge

Because of the high protein content and rich meat quality of crayfish Procambarus clarkii, it has become widely popular in China in recent years and has a high economic value. When P. clarkii is stimulated by heavy metals, it reacts to oxidation. P. clarkii has evolved antioxidant defense systems, including antioxidant enzymes such as catalase (CAT). The hexavalent form of Cr (VI) is a pathogenic factor that is of particular concern in aqueous systems because of its great toxicity to living organisms. In this study, we characterized the transcriptome of P. clarkii using a RNA sequencing method and performed a comparison between K₂Cr₂O₇-treated samples and controls. In total, 34,237 unigenes were annotated. We identified 5098 significantly differentially expressed genes (DEGs), including 2536 and 2562 were significantly up-regulated and down-regulated, respectively. In addition, quantitative real time-PCR (qRT-PCR) confirmed the up-regulation of a random selection of DEGs. Our results contribute to a more comprehensive understanding of the antioxidant defense system used by P. clarkii in response to heavy metal stress.

Transcriptome analysis of differential expressed genes in hepatopancreas of Procambarus clarkii challenged with peptidoglycan

Procambarus clarkii is one of the most economically important species in Chinese aquaculture, and is widely cultured. Infection of P. clarkii populations with bacterial pathogens causes high mortality and great economic loss, therefore disease control is of significant economic importance. P. clarkii is a model system for studying immune responses in invertebrates, and its immune system consists solely of the innate response. In the present study, we examined gene expression related to immune function in P. clarkii in response to pathogen challenge. The transcriptome of hepatopancreas tissue from P. clarkii challenged with peptidoclycan (PGN) was analyzed and compared to control specimens. After assembly and annotation, 48,661 unigenes were identified with an average length of 671.54 bp. A total of 2533 differentially expressed genes (DEGs) were obtained, including 765 significantly up-regulated unigenes and 1757 significantly down-regulated unigenes. Gene ontology (GO) analysis demonstrated 19 biological process subcategories, 16 cellular component subcategories, and 17 molecular function subcategories that were enriched among these DEGs. Enrichment analysis using the Kyoto Encyclopedia of Genes and Genomes (KEGG) database revealed enrichment among immune responses pathways. Taken together, this study not only enriches the existing P. clarkii transcriptome database, but also elucidates immune responses of crayfish that are activated in response to PGN challenge.

Transcriptome Analysis Reveals Potential Antioxidant Defense Mechanisms in Antheraea pernyi in Response to Zinc Stress

The growth and development of the Chinese oak silkworm, Antheraea pernyi, are strongly influenced by environmental conditions, including heavy metal pollution. An excess of heavy metals causes cellular damage through the production of free radical reactive oxygen species. In this study, transcriptome analysis was performed to investigate global gene expression when A. pernyi was exposed to zinc infection. With RNA sequencing (RNA-Seq), a total of 25 795 510 and 38 158 855 clean reads were obtained from zinc-treated and control fat body libraries, respectively. We identified 2399 differential expression genes (DEGs) (1845 upregulated and 544 downregulated genes) in the zinc-treated library. In addition, Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed that these DEGs were related to the peroxisome pathway that was associated with antioxidant defense. Our results suggest that fat bodies of A. pernyi constitute a strong antioxidant defense against heavy metal contamination.

Comparative transcriptome analysis of silkworm, Bombyx mori colleterial gland suggests their functional role in mucous secretion

Colleterial glands (CG) present in the body of adult female of Bombyx mori, which can help adhere eggs on the surface of the host plants. Although this organ has been known for centuries, only morphology and its secretions have been studied. Their gene expression profiles and physiological roles remain largely unknown. Aided by high-throughput next generation sequencing (NGS), we reported the comparative transcriptome analysis of CG isolated from the H9 and the P50 strains of Bombyx mori. A total of 19,896,957 and 20,446,366 clean reads were obtained from CG of H9 and the P50 strains, respectively; then differential expression analysis was performed, and 1,509 differentially expressed genes (DEGs) were identified. Among them, 1,001 genes are up-regulated and 508 genes are down-regulated in P50 individuals compared with H9 individuals. The enrichment of GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) of DEGs confirmed that many DEGs were associated with "Amino acid transport and metabolism", "Nucleotide transport and metabolism", and "Inorganic ion transport and metabolism", 25 of the DEGs related to the "ECM-receptor interaction passway", "sphingolipid metabolism passway", and "amino sugar and nucleotide sugar metabolism passway" were potentially involved in the process of CG development and mucus secretion. According to these data, we hypothesized that CG play an important role in providing favorable physiological environment for the glue secretion formation. In addition, GO enrichment and differential expression analysis of the DEGs in the CG indicate that this gland may be involved in the transporting of small solutes such as sugars, ions, amino acids and nucleotide sugar to the CG. Our findings lay the foundation for further research on CG function.