Characterization and expression analysis of peroxiredoxin family genes from the silkworm Bombyx mori in response to phoxim and chlorpyrifos

Design and elucidation of an insecticide from natural compounds targeting mitochondrial proteins of Aedes aegypti

Developing new pesticides poses a significant challenge in designing next-generation natural insecticides that selectively target specific pharmacological sites while ensuring environmental friendliness. In this study, we aimed to address this challenge by formulating novel natural pesticides derived from secondary plant metabolites, which exhibited potent insecticide activity. Additionally, we tested their effect on mitochondrial enzyme activity and the proteomic profile of Ae. aegypti, a mosquito species responsible for transmitting diseases. Initially, 110 key compounds from essential oils were selected that have been reported with insecticidal properties; then, to ensure safety for mammals were performed in silico analyses for toxicity properties, identifying non-toxic candidates for further investigation. Subsequently, in vivo tests were conducted using these non-toxic compounds, focusing on the mosquito's larval stage. Based on the lethal concentration (LC), the most promising compounds as insecticidal were identified as S-limonene (LC50 = 6.4 ppm, LC95 = 17.2 ppm), R-limonene (LC50 = 9.86 ppm, LC95 = 27.7 ppm), citronellal (LC50 = 40.5 ppm, LC95 = 68.6 ppm), R-carvone (LC50 = 61.4 ppm, LC95 = 121 ppm), and S-carvone (LC50 = 62.5 ppm, LC95 = 114 ppm). Furthermore, we formulated a mixture of R-limonene, S-carvone, and citronellal with equal proportions of each compound based on their LC50. This mixture specifically targeted mitochondrial proteins and demonstrated a higher effect that showed by each compound separately, enhancing the insecticidal activity of each compound. Besides, the proteomic profile revealed the alteration in proteins involved in proliferation processes and detoxification mechanisms in Ae. aegypti. In summary, our study presents a formulation strategy for developing next-generation natural insecticides using secondary plant metabolites with the potential for reducing the adverse effects on humans and the development of chemical resistance in insects. Our findings also highlight the proteomic alteration induced by the formulated insecticide, showing insight into the mechanisms of action and potential targets for further exploration in vector control strategies.

Peroxiredoxin 1 transfer during mating protects eupyrene sperm against oxdative stress in Grapholita molesta

BACKGROUND

Each Grapholita molesta female only copulates once during its lifetime and thus must maintain the viability of stored eupyrene sperm for male reproductive success. The male ejaculate comprises abundant accessory gland proteins produced by the male accessory gland (AG), and many of which are major effectors for sperm storage and maintenance.

RESULTS

Here, we reported that an antioxidant protein, peroxiredoxin 1 (GmolPrx1), secreted by the male AG, is essential for protecting eupyrene sperm from oxidative stress and maintaining their quality during storage in the female bursa copulatrix (BC). Our data showed that GmolPrx1 is highly expressed in the AG of sexually mature males. The GmolPrx1 protein is localized to the cytoplasm of AG cells and delivered to the female BC during mating. Knockdown of GmolPrx1 strongly decreased the fertility of mated females. Additionally, we evaluated oxidative status in the spermatophore of females and found that the content of hydrogen peroxide increased significantly after mating with GmolPrx1 knockdown males. Finally, the quality assessment of eupyrene sperm demonstrated that the plasma membrane integrity, acrosome integrity, and DNA integrity were all severely impaired in the spermatophore of females after mating with GmolPrx1 knockdown males, which may contribute to the fertility decline in males.

CONCLUSION

Our current data demonstrated that activities of eupyrene sperm stored in females can be significantly impaired by enhanced oxidative stress through knocking down of GmolPrx1 in males. Our finding thus may further lay new foundations for the control of G. molesta through suppressing their populations by manipulating male reproductive genes. © 2023 Society of Chemical Industry.

A thioredoxin peroxidase protects Pieris rapae from oxidative stress induced by chlorantraniliprole exposure

Chlorantraniliprole (CAP) is an insecticide widely used to control the small white butterfly (SWB), Pieris rapae. Exposure to CAP can cause oxidative injury in SWB; however, it is unclear if antioxidant enzymes are involved in the defense process. In this study, a thioredoxin peroxidase (PrTPX1) gene was identified from SWB by using a homology search method. The gene encoded a 195 amino-acid PrTPX1 protein. Sequence characteristics and phylogenetic analysis indicated that PrTPX1 was a typical "2-Cys" TPX, and the PrTPX1 gene consisted of four exons and three introns. Reverse transcription-quantitative polymerase chain reaction analysis indicated that the messenger RNA levels of PrTPX1 were highest in third-, fourth- and fifth-instar larval stages and in the larval midgut. Treatment with sublethal doses (LD₂₀ and LD₅₀ ) of CAP for 6, 12, 18, and 24 h resulted in increased H₂ O₂ concentration in SWB larvae, indicating insecticide-induced oxidative stress. The transcriptional levels of PrTPX1 were significantly enhanced in larvae exposed to CAP. Recombinant PrTPX1 protein was expressed in Escherichia coli. Enzymatic assay revealed that the protein displayed antioxidant activity and was able to protect against oxidative challenge. These results indicated that PrTPX1 plays an important role in oxidative stress responses and may contribute to the CAP tolerance in SWB.

Glutaredoxins and thioredoxin peroxidase involved in defense of emamectin benzoate induced oxidative stress in Grapholita molesta

Glutaredoxins (Grxs) and thioredoxin peroxidases (Tpxs) are major antioxidant enzyme families involved in regulating cellular redox homeostasis and in defense of enhanced oxidative stress through scavenging reactive oxygen species (ROS). However, the functions of these enzymes have not been reported in the oriental fruit moth, Grapholita molesta (Busck), a worldwide pest of stone and pome fruits. Here, we identified four new antioxidant genes, GmGrx, GmGrx3, GmGrx5, and GmTpx which were induced by exposure with emamectin benzoate, a commonly used biopesticide for G. molesta control. Other environmental factors (low and high temperatures, Escherichia coli and Metarhizium anisopliae) also significantly induced the expression of these genes. After GmGrx or GmTpx silenced by RNA interference (RNAi), the percentage of larval survival to emamectin benzoate were significantly decreased, demonstrating that GmGrx and GmTpx are involved in protecting G. molesta from stresses induced by emamectin benzoate. Furthermore, silenced GmGrx, GmGrx3, GmGrx5, or GmTpx significantly enhanced the enzymatic activities of superoxide dismutase (SOD) (except GmTpx) and peroxidase (POD), as well as the contents of hydrogen peroxide and metabolites ascorbate. Taken together, our results suggest that GmGrx, GmGrx3, GmGrx5, and GmTpx may play critical roles in antioxidant defense. Specially, GmGrx and GmTpx contribute to the defense of oxidative damage induced by exposure to emamectin benzoate through scavenging excessive ROS in G. molesta. Our findings provided a theoretical basis for understanding functions of insect glutaredoxin and peroxidase systems.

Identification and molecular characterization of peroxiredoxin 2 in grass carp (Ctenopharyngodon idella)

Peroxiredoxin (Prx), also named thioredoxin peroxidase (TPx), is a selenium independent antioxidant enzyme that can protect organisms from oxidative damage caused by reactive oxygen species (ROS) and is important for immune responses. In this study, the molecular cloning and characterization of a Prx2 homologue (CiPrx2) were described from grass carp (Ctenopharyngodon idella). The full-length cDNA of CiPrx2 was 1163 bp containing 5'-untranslated region (UTR) of 52 bp, a 3'-UTR of 517 bp with the putative polyadenylation consensus signal (AATAAA), an open reading frame (ORF) of 594 bp encoding polypeptides of 197 amino acids with a predicted molecular mass of 21.84 kDa and theoretical isoelectric point of 5.93. The analysis results of multiple sequence alignment and phylogenetic tree confirmed that CiPrx2 belong to the typical 2-Cys Prx subfamily. The CiPrx2 mRNA was ubiquitously expressed in all tested tissues. The temporal expression of CiPrx2 were differentially induced infected with grass carp reovirus (GCRV), polyinosinic:polycytidylic acid (poly I:C) and lipopolysaccharide (LPS) in liver and spleen. Subcellular localization of CiPrx2-GFP fusion proteins were only distributed in the cytoplasm. The purified recombinant CiPrx2 possessed an apparent antioxidant activity and could protect DNA against oxidative damage. Finally, CiPrx2 proteins could obviously inhibit H₂O₂ and heavy metal toxicity. However, further researches are needed to better understand the regulation of CiPrx2 under oxidative stresses.

Identification of glutathione-S-transferase genes by transcriptome analysis in Meteorus pulchricornis (Hymenoptera: Braconidae) and their expression patterns under stress of phoxim and cypermethrin

Meteorus pulchricornis (Wesmael) (Hymenoptera: Braconidae) is a preponderant endoparasitoid wasp, attacking the larvae of many lepidopteran pests. We present the first body transcriptome dataset for M. pulchricornis. In total, 50,781,796 clean reads were obtained and 33,144 unigenes were assembled; 15,458 unigenes showed a significant similarity (E value < 10^-5) to known proteins in the NCBI non-redundant protein database. Gene ontology and cluster of orthologous group analyses were performed to classify the functions of genes. To better understand the role of glutathione-S-transferases (GSTs) in detoxification mechanism in M. pulchricornis, we identified seventeen GST genes (MpulGSTs) from the body transcriptome. Among these, fifteen MpulGSTs belonged to cytosolic GSTs and the other two belonged to microsomal classes. The cytosolic GSTs were classified into four different clades: four in delta, three in omega, seven in sigma, and one in zeta. The expression levels of these MpulGSTs after exposure to sub-lethal concentrations of phoxim and cypermethrin were determined using real-time quantitative polymerase chain reaction: seven MpulGSTs (MpulGSTD3, MpulGSTS1, MpulGSTS2, MpulGSTS4, MpulGSTS6 MpulGSTO3, and MpulGSTmic1) and 11 MpulGSTs (MpulGSTD1, MpulGSTD2, MpulGSTD3, MpulGSTO2, MpulGSTS1, MpulGSTS2, MpulGSTS3, MpulGSTS4, MpulGSTS5, MpulGSTS7, and MpulGSTmic1) were highly expressed, respectively. These results suggested that GST genes may play a pivotal role in detoxification process in M. pulchricornis. Our findings would provide a theoretical base for elucidating insecticide susceptibility and should promote functional research on specific GST genes in parasitoid wasps.

The silk gland damage and the transcriptional response to detoxifying enzymes-related genes of Bombyx mori under phoxim exposure

Silk gland is a major organ of Bombyx mori for the synthesis and secretion of silk protein. Phoxim exposure can be toxic to B. mori and causes a decrease of fibroin synthesis, finally affecting the silk production in industry. To study the mechanism of metabolism and detoxification of silk gland under phoxim exposure, we measured the residual quantity of phoxim in silk gland and hemolymph after phoxim exposure, and the detoxifying enzymes-related genes and enzyme activity were also investigated. Results indicated that the residual amount of phoxim existed up to 24 h in silk gland compared with that in hemolymph, suggesting that phoxim can accumulate in the silk glands within a certain time course. The transcriptional levels of PI3K/Akt genes, including Akt, Tor1, p70s6k and 4e-bp, were up-regulated by 6.919, 1.358, 10.766 and 7.708-fold, respectively. The expression of two downstream genes (CncC and Keap1) was up-regulated by 1.939 and 3.373-fold, respectively. In addition, the transcriptional levels of detoxification-related genes including CYP6AB, CYP306A, CarE2, GST1 and GSTd1 were up-regulated by 1.731, 1.221, 1.366, 1.376 and 6.591-fold, respectively. The enzymatic activity of CYP450, CarE and GST were increased over time. These results provided possible insights into the injury of silk gland and the transcriptional response to detoxifying enzymes-related genes in silkworm after phoxim exposure.

Molecular characterization of a typical 2-Cys thioredoxin peroxidase from the Asiatic rice borer Chilo suppressalis and its role in oxidative stress

In insects, thioredoxin peroxidase (TPX) plays an important role in protecting against oxidative damage. However, studies on the molecular characteristics of TPXs in the Asiatic rice borer, Chilo suppressalis, are limited. In this work, a cDNA sequence (CsTpx3) encoding a TPX was identified from C. suppressalis. The deduced CsTPX3 protein shares high sequence identity and two positionally conserved cysteines with orthologs from other insect species, and was classified as a typical 2-Cys TPX. CsTpx3 was expressed most highly during the fifth-instar larval stage, and transcripts were most abundant in the midgut. Recombinant CsTPX3 protein expressed in Escherichia coli displayed the expected peroxidase activity by removing H₂ O₂ . Furthermore, CsTPX3 protected DNA from oxidative damage, and E. coli cells overexpressing CsTPX3 exhibited long-term resistance to oxidative stress. Exposure to various oxidative stressors, such as cold (8°C), heat (35°C), bacteria (E. coli), and two insecticides (chlorpyrifos and lambda-cyhalothrin), significantly upregulated transcription of CsTpx3. However, exposure to abamectin had no such effect. Our results provide valuable information for future studies on the antioxidant mechanism in this insect species.

Changes in glucose metabolism and mRNA expression of IRS-2 in rats exposed to phoxim and the protective effects of vitamin E

Research has shown that organophosphorus pesticides impair glucose homeostasis and cause insulin resistance and type 2 diabetes. The current study investigates the influence of phoxim on insulin signaling pathways and the protective effects of vitamin E. Phoxim (180 mg kg-1) and VE (200 mg kg-1) were administered orally to Sprague-Dawley rats over a period of 28 consecutive days. After exposure to phoxim, the animals showed glucose intolerance and hyperinsulinemia during glucose tolerance tests, and insulin tolerance tests demonstrated an impaired glucose-lowering effect of insulin. Phoxim increases the fasting glucose, insulin and cholesterol levels, as well as the liver hexokinase activity (HK) significantly while decreasing the high density lipoprotein (HDL) cholesterol, and glycogen content in the liver and skeletal muscles observably. Furthermore, we observed an increase of insulin resistance biomarkers and a decrease of insulin sensitivity indices. The insulin receptor substrate (IRS)-2 mRNA expressions of liver and skeletal muscles were down-regulated by phoxim, while the expression of IRS-1 showed no difference. There were no differences in triglycerides, LDL-cholesterol, and fasting glucose treated with phoxim. On the basis of biochemical and molecular findings, phoxim has been determined to impair glucose homeostasis through insulin resistance and insulin signaling pathway disruptions resulting in a reduced function of insulin in hepatocytes and muscles. VE supplementation reduced the fasting glucose, increased the glycogen content and HDL-cholesterol, but did not reduce the insulin resistance indices, when phoxim-treated rats were compared to VE supplemented rats. Overall, this study shows that vitamin E modifies the phoxim toxicity in rats only to a moderate degree.

Identification and characterization of six peroxiredoxin transcripts from mud crab Scylla paramamosain: The first evidence of peroxiredoxin gene family in crustacean and their expression profiles under biotic and abiotic stresses

The peroxiredoxins (Prxs) define a novel and evolutionarily conserved superfamily of peroxidases able to protect cells from oxidative damage by catalyzing the reduction of a wide range of cellular peroxides. Prxs have been identified in prokaryotes as well as in eukaryotes, however, the composition and number of Prxs family members vary in different species. In this study, six Prxs were firstly identified from the mud crab Scylla paramamosain by RT-PCR and RACE methods. Six SpPrxs can be subdivided into three classes: (a) three typical 2-Cys enzymes denominated as Prx1/2, 3, 4, (b) two atypical 2-Cys enzymes known as Prx5-1 and Prx5-2, and (c) a 1-Cys isoform named Prx6. The evolutionarily conserved signatures of peroxiredoxin catalytic center were identified in all six SpPrxs. Phylogenetic analysis revealed that SpPrx3, SpPrx4, SpPrx5s and SpPrx6 were clearly classified into Prx3-6 subclasses, respectively. Although SpPrx1/2 could not be grouped into any known Prx subclasses, SpPrx1/2 clustered together with other arthropods Prx1 or unclassified Prx and could be classified into the typical 2-Cys class. The comparative and evolutionary analysis of the Prx gene family in invertebrates and vertebrates were also conducted for the first time. Tissue-specific expression analysis revealed that these six SpPrxs were expressed in different transcription patterns while the highest expression levels were almost all in the hepatopancreas. Quantitative RT-PCR analysis exhibited that the gene expression profiles of six SpPrxs were distinct when crabs suffered biotic and abiotic stresses including the exposures of Vibrio alginolyticus, poly (I:C), cadmium and hypoosmotic salinity, suggesting that the SpPrxs might play different roles in response to various stresses. The recombinant proteins including the SpPrx1/2, SpPrx4, SpPrx5-1 and SpPrx6 were purified and the peroxidase activity assays indicated that all these proteins can reduce H₂O₂ in a typical DTT-dependent manner. To our knowledge, this is the first study about the comprehensive characterization of Prx gene family in Scylla paramamosain and even in crustaceans. These results would broaden the current knowledge of the whole Prx family as well as be helpful to understand and clarify the evolutionary pattern of Prx family in invertebrate and vertebrate taxa.