Effects of added CeCl3 on resistance of fifth-instar larvae of silkworm to Bombyx mori nucleopolyhedrovirus infection

Transcriptomics and interactomics during the primary infection of an SfNPV baculovirus on Spodoptera frugiperda larvae

The fall armyworm (FAW), Spodoptera frugiperda, has been the most devastating pest of corn as well as of other crops in America, and more recently in Africa and Asia. The development of resistance to chemical insecticides led the search for environmentally friendly biological alternatives such as baculoviruses. This study focuses on the primary infection of the baculovirus SfNPV-Ar in the FAW's midgut epithelium, by analyzing the differential expression of transcripts in excised midguts at 6, 12, and 24 h post-infection (hpi), and predicted their interactions. Interaction of viral factors with the infected midgut tissue could alters various cellular processes, such as the apoptotic system due to the up-regulation observed of FABP at 6 hpi and of HSP90 at 24 hpi, along with the down-regulated PRX at 6 hpi and FABP transcripts between 12 and 24 hpi. Changes in transcript regulation could affect the cellular architecture of infected cells due to up-regulation of ARP 2/3 at 6 and 12 hpi, followed by down-regulation at 24 hpi. In relation to protein folding proteins, HSP90 was up-regulated at 24 hpi and PDI was down-regulated between 6 and 12 hpi. With respect to metabolism and cellular transport, AcilBP and ATPS0 were up regulated at 6 hpi and 12 hpi, respectively. In reference to transcription and translation up-regulation of RPL11 at 6 hpi and of FPN32 and RPL19 at 24 hpi was detected, as well as the down-regulation of RPL19 at 6 hpi, of PDI and RPL7 at 12 hpi, and of FABP at 24 hpi. In conclusion, gene regulation induced by viral infection could be related to the cytoskeleton and cellular metabolism as well as to oxidative stress, apoptosis, protein folding, translation, and ribosomal structure. The results presented in this work are an approach to understanding how the virus takes control of the general metabolism of the insect host during the primary infection period.

Bombyx mori nucleopolyhedrovirus F-like protein Bm14 is a factor for viral-induced cytopathic effects via regulating oxidative phosphorylation and cellular ROS levels

Bombyx mori nucleopolyhedrovirus (BmNPV) is highly pathogenic to Bombyx mori, silkworm, which causes serious cytopathic effects (CPEs) during infection. However, the role of viral protein in the virus-induced CPEs remains unclear. Here, we discovered that BmNPV infection induced severe CPEs including titer-dependent cell floating and changes in cellular surface morphology. Further explorations revealed the involvement of F-like protein (Bm14), a viral envelope protein, in inducing cytotoxicity and detachment of adherent BmN cells, and its disruption significantly impaired the virus infection-mediated CPEs. Intriguingly, transcriptomic analysis identified the tight association of Bm14 deletion with the activation of cellular oxidative phosphorylation pathway, consistent with the elevated mitochondrial membrane potential (MMP) levels and ATP concentrations as well as reduced ROS levels. Collectively, our results characterized for the first time the novel role of Bm14 in accelerating viral-induced cytopathogenicity via suppressing the cellular oxidative phosphorylation levels and upregulating the ROS levels.

Antioxidant Systems as a Response to Midgut Cellular of Bombyx mori Lineu, 1758 (Lepidoptera: Bombycidae) Infection for Baculoviruses

Bombyx mori nucleopolyhedrovirus (BmNPV) is a DNA virus that infects different tissues in Bombyx mori at immature stage. Caterpillars become infected after ingesting polyhedral occlusion bodies (POB) present in contaminated mulberry leaves and spread through the body after passing the epithelium of the midgut. As this organ is responsible for digestion, most absorption of nutrients requires an intact epithelium to maintain gastrointestinal physiology. Considering the importance of this organ in the feeding of caterpillars and in the production of quality silk threads, and because it is also the first barrier faced by the BmNPV, the study analyzed details of cytopathological events in the intestinal cells as well as evaluated the action of the antioxidant systems as a response to cellular infection. For this purpose, B. mori hybrid caterpillars of fifth instar were inoculated with a suspension of 7.8 × 107 POB ml-1 and, from the first to the eighth day post-inoculation (dpi), segments of the midgut were collected and processed for light and electronic microscopy. The nuclei of columnar cells showed polyhedric occlusion bodies in the seventh dpi and fragmentation of those cells, with peritrophic matrix disorganization. Analysis of antioxidant systems shows some moments of changes of the catalase enzymes and superoxide dismutase. Analysis of the cholinergic system revealed changes only at the beginning of the infection. Thus, the article acknowledges the antioxidant system as a barrier to stop viral infection, albeit it cannot stop infection from occurring, once a coevolutionary bond is maintained between virus and host.

Effects of 200 Gy 60Co-γ Radiation on the Regulation of Antioxidant Enzymes, Hsp70 Genes, and Serum Molecules of Plutella xylostella (Linnaeus)

The diamondback moth, Plutella xylostella (Linnaeus), is one of the notorious pests causing substantial loses to many cruciferous vegetables across the nations. The effects of ⁶⁰Co-γ radiation on physiology of P. xylostella were investigated and the results displayed that 200 Gy irradiation significantly alters the antioxidant enzyme regulation in six-day-old male pupae of P. xylostella. First, in our research, we detected Oxidase system and stress response mechanism of irradiated pupae, the results displayed that 200 Gy irradiation significantly alters the antioxidant enzyme regulation in six-day-old male pupae of P. xylostella. The levels of superoxide dismutase (SOD) and catalase (CAT) were increased significantly in contrast the level of peroxidase (POD) and glutathione S-transferase (GST) were decreased in 12–24 h post-treatment. The heat shock proteins (Hsps) gene expression level was significant increasing, maximum > 2-folds upregulation of genes were observed in peak. However, they also had a trend of gradual recovery with development. Second, we detected the testis lactate dehydrogenase (LDH) and acid phosphatase (ACP) activity found that in male adults testis they increased significantly than control during its development. Thus the present research investigation highlights that the ⁶⁰Co-γ radiation treatments alters the physiological development of diamondback moth. The results showed that 200 Gy dosage resulted in stress damage to the body and reproductive system of the diamondback moth.

Molecular mechanisms of silk gland damage caused by phoxim exposure and protection of phoxim-induced damage by cerium chloride in Bombyx mori

It is known that exposure to organophosphorus pesticides (OP) including phoxim can produce oxidative stress, neurotoxicity, and greatly attenuate cocooning rate in the silkworm, Bombyx mori. Cerium treatment has been demonstrated to relieve phoxim-induced toxicity in B. mori; however, very little is known about the molecular mechanisms of silk gland injury due to OP exposure and protection of gland damage due to cerium pretreatment. The aim of this study was to evaluate silk gland damage and its molecular mechanisms in phoxim-induced silkworm toxicity and the protective mechanisms of cerium following exposure to phoxim. The results showed that phoxim exposure resulted in severe gland damage, reductions in protein synthesis and the cocooning rate of silkworms. Cerium (Ce) attenuated gland damage caused by phoxim, promoted protein synthesis, increased the antioxidant capacity of the gland and increased the cocooning rate of B. mori. Furthermore, digital gene expression data suggested that phoxim exposure led to significant up-regulation of 714 genes and down-regulation of 120 genes. Of these genes, 122 were related to protein metabolism, specifically, the down-regulated Ser2, Ser3, Fib-L, P25, and CYP450. Ce pretreatment resulted in up-regulation of 162 genes, and down-regulation of 141 genes, importantly, Ser2, Ser3, Fib-L, P25, and CYP333B8 were up-regulated. Treatment with CeCl3 + phoxim resulted in higher levels of Fib-L, P25, Ser2, Ser3, CAT, TPx, and CYP333B8 expression in the silk gland of silkworms. These findings indicated that Ce increased cocooning rate via the promotion of silk protein synthesis-related gene expression in the gland under phoxim-induced toxicity. These findings may expand the application of rare earths in sericulture.

Molecular Signatures of Reduced Nerve Toxicity by CeCl3 in Phoxim-exposed Silkworm Brains

CeCl3 can reduce the damage caused by OP pesticides, in this study we used the brain of silkworms to investigate the mechanism of CeCl3 effects on pesticide resistance. The results showed that phoxim treatments led to brain damages, swelling and death of neurons, chromatin condensation, and mitochondrial damage. Normal nerve conduction was severely affected by phoxim treatments, as revealed by: increases in the contents of neurotransmitters Glu, NO, and ACh by 63.65%, 61.14%, and 98.54%, respectively; decreases in the contents of 5-HT and DA by 53.19% and 43.71%, respectively; reductions in the activities of Na(+)/K(+)-ATPase, Ca(2+)/Mg(2+)-ATPase, and AChE by 85.27%, 85.63%, and 85.63%, respectively; and increase in the activity of TNOS by 22.33%. CeCl3 pretreatment can significantly reduce such damages. Results of DGE and qRT-PCR indicated that CeCl3 treatments significantly upregulated the expression levels of CYP4G23, cyt-b5, GSTs-σ1, ace1, esterase-FE4, and β-esterase 2. Overall, phoxim treatments cause nerve tissue lesions, neuron death, and nerve conduction hindrance, but CeCl3 pretreatments can promote the expression of phoxim resistance-related genes in silkworm brains to reduce phoxim-induced damages. Our study provides a potential new method to improve the resistance of silkworms against OP pesticides.

Mechanisms of larval midgut damage following exposure to phoxim and repair of phoxim-induced damage by cerium in Bombyx mori

Bombyx mori is an important economic animal for silk production. However, it is liable to be infected by organophosphorus pesticide that can contaminate its food and growing environment. It has been known that organophosphorus pesticide including phoxim exposure may damage the digestive systems, produce oxidative stress and neurotoxicity in silkworm B. mori, whereas cerium treatment has been demonstrated to relieve phoxim-induced toxicity in B. mori. However, very little is known about the molecular mechanisms of midgut injury due to phoxim exposure and B. mori protection after cerium pretreatment. The aim of this study was to evaluate the midgut damage and its molecular mechanisms, and the protective role of cerium in B. mori following exposure to phoxim. The results showed that phoxim exposure led to severe midgut damages and oxidative stress; whereas cerium relieved midgut damage and oxidative stress caused by phoxim in B. mori. Furthermore, digital gene expression suggested that phoxim exposure led to significant up-regulation of 94 genes and down-regulation of 52 genes. Of these genes, 52 genes were related with digestion and absorption, specifically, the significant alterations of esterase, lysozyme, amylase 48, and lipase expressions. Cerium pretreatment resulted in up-regulation of 116 genes, and down-regulation of 29 genes, importantly, esterase 48, lipase, lysozyme, and α-amylase were up-regulated. Treatment with Phoxim + CeCl3 resulted in 66 genes up-regulation and 39 genes down-regulation; specifically, levels of esterase 48, lipase, lysozyme, and α-amylase expression in the midgut of silkworms were significantly increased. Therefore, esterase 48, lipase, lysozyme, and α-amylase may be potential biomarkers of midgut toxicity caused by phoxim exposure. These findings may expand the application of rare earths in sericulture.

Antioxidant enzymes as defense mechanism against oxidative stress in midgut tissue and hemocytes of Bombyx mori larvae subjected to various stressors

In this study, larvae of silkworm Bombyx mori were subjected to low temperature, hypoxia, and viral infection to evaluate stressor-mediated oxidative stress (OS) and the induction of antioxidant enzymes (AOEs). Exposure to cold, hypoxia, and nuclear polyhedral virus for 24 h resulted in a significant increase in hydrogen peroxide generation with concomitant increase in lipid peroxidation (LPO) and protein carbonyl levels in midgut and hemocytes. AOEs such as superoxide dismutase and catalase also increased significantly in both the tissues and the increased AOEs reverted to control values during recovery. Ontogenic stages of the larvae showed a diminishing ability of the tissues to overcome OS induced by the stressors. A significant increase in AOE activity during short stress period indicated a possible transitory defense mechanism to avoid OS-induced cell damage.

Cerium chloride improves protein and carbohydrate metabolism of fifth-instar larvae of Bombyx mori under phoxim toxicity

The organophosphorus pesticide poisoning of the silkworm Bombyx mori is one of the major events causing serious damage to sericulture. Added low-dose rare earths are demonstrated to increase resistance in animals. However, very little is known about whether or not added CeCl₃ can increase resistance of silkworm to phoxim poisoning. The present findings suggested that added CeCl₃ to mulberry leaves markedly increased contents of protein, glucose and pyruvate, and carbohydrate metabolism-related enzyme activities, including lactate dehydrogenase, succinate dehydrogenase and malate dehydrogenase, and attenuated free amino acids, urea, uric acid and lactate levels and inhibited the protein metabolism-related enzymes activities, such as protease, alanine aminotransferase and aspartate aminotransferase in the haemolymph of B. mori, under phoxim toxicity. These findings suggest that added CeCl₃ may improve protein and carbohydrate metabolisms, thus leading to increases of growth and survival rate of B. mori under phoxim stress.