Potential detoxification of gossypol by UDP-glycosyltransferases in the two Heliothine moth species Helicoverpa armigera and Heliothis virescens

Heterologous Overexpression of Cytochrome P450BM3 from Bacillus megaterium and Its Role in Gossypol Reduction

Gossypol is a polyphenolic toxic compound present in cotton plants. To determine whether the candidate cytochrome P450BM3 enzymes could reduce gossypol in vitro, functional recombinant cytochrome P450BM3 enzymes were successfully expressed in E. coli. Site-directed mutagenesis generated mutants (R162H, R162K, Q129H, Q129N) to explore structural determinants of catalytic efficiency. Both wild-type P450BM3 and mutants exhibited significant ability to reduce gossypol levels, with R162H and R162K showing 33.4% and 24.2% reduced catalytic efficiency compared with the wild-type enzyme, respectively. Q129H and Q129N mutants maintained comparable catalytic efficiency to the wild type. Metabolomic profiling revealed two distinct reducing pathways catalyzed by wild-type P450BM3 and its mutants (R162H/Q129H), involving decarboxylation, hydroxylation, and C-C bond cleavage. This study demonstrated the feasibility of P450BM3 as a highly efficient biocatalyst for reducing gossypol levels, speculated that Arg162 might be a critical active residue, and hypothesized the potential pathways by which P450BM3 catalyzes the reduction of gossypol content, thereby providing a theoretical foundation for the enzymatic reduction of gossypol.

Characterization of a uridine diphosphate (UDP)-glycosyltransferase gene associated with abamectin resistance in two-spotted spider mite, Tetranychus urticae

Uridine diphosphate (UDP)-glycosyltransferase (UGT) belongs to detoxification enzyme glycosylating lipophilic xenobiotic compounds in various living organisms. Tetranychus urticae is a notorious pest due to its significant threat to crop production and serious resistance problem worldwide. However, the function of UGT gene in contributing to pesticide resistance in T. urticae remained largely unknown. In this study, it was found that the laboratory selected abamectin-resistant (AbR) strain had developed over 20,000-fold resistance compared with the susceptible strain (SS). After being treated with abamectin, the activities of UGTs, and the transcription of TuUGT201D3 in the AbR strain were significantly higher than those in SS. Molecular docking indicated that the UGT201D3 protein exhibited high binding capacity with abamectin, suggesting the potential interaction between them. Furthermore, knock-down the transcription of TuUGT201D3 led to the decrease of activities of UGTs, in addition, the mortalities of AbR strain (58.4%) will significantly increase compared to control (41.1%) under 48 h of abamectin treatment. Those findings elucidated that TuUGT201D3 was correlated with abamectin resistance in T. urticae.

Probiotic Fermentation of Defatted Cottonseed Meal for Sustainable Foods and Non-Food Applications

Cottonseed is a valuable source of high-quality proteins and oils. Defatted cottonseed meal (DCSM), a by-product of cottonseed oil extraction, holds significant potential as a sustainable protein resource. This review outlines the chemical composition, structural features, and unique properties of cottonseed, with a focus on its inherent antinutritional factors, such as gossypol. Strategies for enhancing the utilization of DCSM as a protein source are systematically evaluated, including physical, chemical, and biological methods used to eliminate or reduce antinutritional components. Among these, microbial fermentation, particularly solid-state fermentation, is highlighted as a promising, eco-friendly approach for detoxification and nutritional improvement. This review further discusses critical factors influencing the removal of anti-nutritional compounds, such as pretreatment methods, fermentation parameters, and microbial strains. The efficacy of probiotic strains (e.g., Bacillus and yeasts) in enhancing the protein digestibility, amino acid profiles, and functional properties of DCSM is discussed. Additionally, recent advances in the application of fermented cottonseed protein in foods (e.g., animal feed, functional peptides, and food additives) and non-food sectors (e.g., biofuels and bioplastic) are explored. The integration of probiotic-driven fermentation processes is proposed as a strategy to exploit the full nutritional and economic potential of DCSM, paving the way for its broader and sustainable use in foods and non-food applications.

Contribution of UDP-glycosyltransferases to clothianidin resistance in Bradysia odoriphaga

Uridine diphosphate glycosyltransferases (UGTs) play critical roles in xenobiotic detoxification and are involved in insecticide resistance. In this study, UGT inhibitors, sulfinpyrazone and 5-nitrouracil, exhibited significant synergistic effects on clothianidin in the clothianidin-resistant strain (CL-R) of Bradysia odoriphaga. UGT enzyme content was significantly higher in the CL-R strain than in the susceptible strain (SS), and both the SS and CL-R strains showed a significant upregulation of UGT content after exposure to clothianidin. Two UGT genes, UGT36M1 and UGT306K1, were significantly overexpressed in the CL-R strain. UGT36M1 was predominantly expressed in the fat body, and UGT306K1 exhibited high levels of expression in the Malpighian tubules and midgut. UGT36M1 and UGT306K1 in the SS strain were significantly upregulated in response to clothianidin exposure. The silencing of UGT36M1 and UGT306K1 significantly enhanced the susceptibility of B. odoriphaga larvae to clothianidin. Furthermore, transgenic overexpression of UGT36M1 and UGT306K1 in Drosophila melanogaster significantly increased the tolerance of fruit flies to clothianidin. These findings provide evidence of the crucial role of UGT36M1 and UGT306K1 in conferring resistance to clothianidin in B. odoriphaga.

A UDP-glucuronosyltransferase gene UGT379A1 involved in detoxification of lufenuron in Diaphorina citri

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is a devastating bacterial disease of commercial citrus. Presently, uridine diphosphate (UDP)-glycosyltransferases (UGTs), have been linked to the detoxification of pesticides, were known as phase II enzymes in the detoxification process. However, the role of UGTs in detoxification of lufenuron in Diaphorina citri is unknown. In this study, we identified a UGT gene, UGT379A1, which was significantly up-regulated under the exposure of lufenuron. The knockdown of UGT379A1 increased the susceptibility of D. citri to lufenuron. In vitro metabolism and Dixon plot analysis indicated that UGT379A1 could deplete lufenuron by sequestration. These results showed that UGT379A1 was involved in the lufenuron detoxification, which provides a theoretical basis for the prevention and control of D. citri.

The UDP-glycosyltransferase UGT352A3 contributes to the detoxification of thiamethoxam and imidacloprid in resistant whitefly

Uridine diphosphate (UDP)-glycosyltransferases are essential phase-II detoxification enzymes that glycosylate lipophilic endogenous and xenobiotic compounds and they are thought to play a role in driving the evolution of insecticide resistance. To examine if the resistance to thiamethoxam and imidacloprid was associated with enhancement of UDP-glycosyltransferase in the whitefly, Bemisia tabaci, we first conducted UDP enzyme activity assays in resistant and sensitive strains in the absence and presence of UGT inhibitors. We found that the UGT enzyme content of resistant whitefly was significantly 5.02- to 10.69-fold higher than that of sensitive whitefly. Individual UGT inhibitors effectively inhibited UGT activity in resistant strains and their effect was synergistic when applied in combination. We then used bioinformatic, molecular, genetic and in silico approaches to determine if UGT352A3 encoded a key enzyme linked to neonicotinoid resistance. In resistant strains, UGT352A3 expression was elevated 1.8- to 6.6-fold compared to susceptible strains, which correlated with higher resistance ratios. RNAi-mediated knockdown of UGT352A3 in resistant whitefly strains significantly heightened their sensitivity to the insecticides, thiamethoxam and imidacloprid. Molecular docking analyses further confirmed a strong binding affinity between UGT352A3 and thiamethoxam and imidacloprid, which supported a role in their metabolism. These findings suggest that UGT352A3 is a critical factor in the development of resistance to thiamethoxam and imidacloprid in whitefly, underscoring its important potential as a new pest resistance management target.

Exploring the adaptation mechanism of Spodoptera litura to xanthotoxin: Insights from transcriptional responses and CncC signaling pathway-mediated UGT detoxification

During the long-term interaction between plants and phytophagous insects, plants generate diverse plant secondary metabolites (PSMs) to defend against insects, whereas insects persistently cause harm to plants by detoxifying PSMs. Xanthotoxin is an insect-resistant PSM that is widely found in plants. However, the understanding of detoxification mechanism of xanthotoxin in insects is still limited at present. In this study, RNA-seq analysis showed that uridine diphosphate (UDP)-glycosyltransferases (UGTs) and cap 'n' collar isoform C (CncC) signaling pathway were specifically retrieved from the midgut and fat body of xanthotoxin-administrated Spodoptera litura larvae. The larvae were sensitive to xanthotoxin when the transcriptional expression and enzyme activity of UGTs were inhibited. Bacteria co-expressing UGT had a high survival rate after exposure to xanthotoxin and displayed high metabolic activity to xanthotoxin, which indicated that UGTs were involved in xanthotoxin detoxification. As the pivotal transcription factors, RNA interference against CncC and its partner, muscle aponeurosis fibromatosis isoform K (MafK), reduced larval tolerance to xanthotoxin as well as UGT expressional levels. Dual-luciferase reporter assay demonstrated that UGT promoter activity was activated by CncC and MafK, and was suppressed once CncC/MafK binding site was mutated. This study revealed that CncC signaling pathway regulated UGT transcriptional expression to mediate xanthotoxin detoxification in S. litura, which will facilitate a better understanding of the adaptive mechanism of phytophagous insects to host plants and provide more valuable insecticide targets for pest control.

Enhanced degradation of exogenetic citrinin by glycosyltransferases in the oleaginous yeast Saitozyma podzolica zwy-2-3

The contamination by the toxin citrinin (CIT), produced by fungi, has been reported in agricultural foods and is known to be nephrotoxic to humans. In this study, we found that CIT could be effectively degraded by the oleaginous yeast Saitozyma podzolica zwy-2-3. Four genes encoding glycosyltransferases (GTs) in S. podzolica zwy-2-3 (SPGTs) were identified by evolutionary and structural analyses. The overexpression of SPGTs enhanced CIT degradation to 0.56 mg/L/h in S. podzolica zwy-2-3 by increasing ATP and glutathione (GSH) contents to oxidize CIT and scavenge reactive oxygen species (ROS). Besides, SPGTs promoted lipid synthesis by 9.3 % of S. podzolica zwy-2-3 under CIT stress. These results suggest that SPGTs in oleaginous yeast play a pivotal role in enhancing CIT degradation and lipid accumulation. These findings provide a valuable basis for the application of GTs in oleaginous yeast to alleviate CIT contamination in agricultural production, which may contribute to food safety.

The fate of a Solanum steroidal alkaloid toxin in the cabbage looper (Trichoplusia ni)

Plants produce complex chemical defenses against herbivores, resulting in the emergence of detoxification strategies in phytophagous insects. While enzymatic detoxification and target site mutagenesis are well-documented, the quantitative contribution of excretion remains less studied. We focus on the cabbage looper (Trichoplusia ni), a generalist herbivore, to elucidate the detoxification of a steroidal alkaloid, solanidine, produced in potato (Solanum tuberosum). Through larval feeding experiments and chemical analysis of metabolites using high-resolution mass spectrometry, we identify solanidine 3-O-β-glucopyranoside and solanidine 3-phosphate as major metabolization products of solanidine. Glycosylation and phosphorylation reactions have not previously been observed in cabbage looper. Modified solanidine derivatives exhibit reduced lipophilicity, preventing passive transport as predicted by physicochemical analyses, and only solanidine was detected in body tissue. In addition, the metabolism of solanidine in a T. ni mutant strain with midgut cadherin protein knocked out was also investigated to examine the potential role of the cadherin, an important receptor for Bt toxins, in steroidal alkaloid detoxification. T. ni cadherin-knockout strain showed lower solanidine conversion (33.9% ± 2.2) and uptake (27.41 ± 0.49 nmol/g) compared to the wild-type strain (51.3% ± 4.1, 33.66 ± 2.48 nmol/g) but similar excretion kinetics. Although solanidine negatively impacted the feeding performance of both strains the cadherin-knockout does not affect the feeding performance. Our study expands the metabolization enzyme repertoire in cabbage loopers, emphasizing the complexity of detoxification mechanisms in generalist herbivores.

Resistance toward Triflumezopyrim Related to Overexpression of SfUGT35A1 and SfGSTd2 in Sogatella furcifera (Hemiptera: Delphacidae)

Sogatella furcifera is a migratory pest that harms rice cultivation. Triflumezopyrim (TFM), a novel insecticide, effectively controls S. furcifera. To guide its scientific application, we studied the TFM resistance mechanisms in resistant strains. Through cross-resistance determination, we found that the strain had cross-resistance to clothianidin. Synergistic and enzyme activities also demonstrated that the TFM resistance was related to the enhancement of glutathione S-transferases and UDP-glycosyltransferases. Meanwhile, SfGSTd2, SfUGT2, and SfUGT35A1 were invariably upregulated in the TFM-resistant strain. RNAi revealed that SfGSTd2 (mortality increasing 33.3-53.3%) and SfUGT35A1 (increasing 33.3-46.7%) significantly increased sensitivity on TFM, while SfUGT35A1 (increasing 40.0-46.7%) also clearly promoted sensitivity toward clothianidin in S. furcifera. The GAL4/UAS system further verified that the overexpression of SfUGT35A1 is involved in the formation of TFM (mortality descending 2.8-52.8%) and clothianidin resistance (mortality descending 11.1-41.7%). Therefore, all results showed that the overexpression of SfGSTd2- and SfUGT35A1-mediated resistance to TFM in S. furcifera.

Comparative transcriptional analysis between susceptible and resistant populations of Aedes (Stegomyia) aegypti (Linnaeus, 1762) after malathion exposure

Aedes aegypti is an important vector of arboviruses, including dengue, chikungunya and Zika. The application of synthetic insecticides is a frequently used strategy to control this insect. Malathion is an organophosphate insecticide that was widely used in Brazil in the 1980s and 1990s to control the adult form of A. aegypti. In situations where resistance to currently used insecticides is detected, the use of malathion may be resumed as a control measure. Many studies have confirmed resistance to malathion, however, comparative studies of differential gene expression of the entire transcriptome of resistant and susceptible insects are scarce. Therefore, understanding the molecular basis of resistance to this insecticide in this species is extremely important. In this paper, we present the first transcriptomic description of susceptible and resistant strains of A. aegypti challenged with malathion. Guided transcriptome assembly resulted in 39,904 transcripts, where 2133 differentially expressed transcripts were detected, and three were validated by RT-qPCR. Enrichment analysis for these identified transcripts resulted in 13 significant pathways (padj < 0.05), 8 associated with down-regulated and 5 with up-regulated transcripts in treated resistant insects. It was possible to divide the transcripts according to the mechanism of action into three main groups: (i) genes involved in detoxification metabolic pathways; (ii) genes of proteins located in the membrane/extracellular region; and (iii) genes related to DNA integration/function. These results are important in advancing knowledge of genes related to resistance mechanisms in this insect, enabling the development of effective technologies and strategies for managing insecticide resistance.

Disarming the defenses: Insect detoxification of plant defense-related specialized metabolites

The ability of certain insects to feed on plants containing toxic specialized metabolites may be attributed to detoxification enzymes. Representatives of a few large families of detoxification enzymes are widespread in insect herbivores acting to functionalize toxins and conjugate them with polar substituents to decrease toxicity, increase water solubility and enhance excretion. Insects have also developed specific enzymes for coping with toxins that are activated upon plant damage. Another source of detoxification potential in insects lies in their microbiomes, which are being increasingly recognized for their role in processing plant toxins. The evolution of insect detoxification systems to resist toxic specialized metabolites in plants may in turn have selected for the great diversity of such metabolites found in nature.

Knocking Out of UDP-Glycosyltransferase Gene UGT2B10 via CRISPR/Cas9 in Helicoverpa armigera Reveals Its Function in Detoxification of Insecticides

The role of insect UDP-glycosyltransferases (UGTs) in the detoxification of insecticides has rarely been reported. A UGT gene UGT2B10 was previously found overexpressed in a fenvalerate-resistant strain of Helicoverpa armigera. Herein, UGT2B10 was cloned, and its involvement in insecticide detoxification was investigated. UGT2B10 was highly expressed in the larvae, mainly in the fat body and midgut. Treatment with UGT inhibitors 5-nitrouracil and sulfinpyrazone significantly enhanced the fenvalerate toxicity. Knocking down UGT2B10 by RNAi significantly increased the larvae mortality by 17.89%. UGT2B10 was further knocked out by CRISPR/Cas9, and a homozygous strain (HD-dUGT2B10) with a C-base deletion at exon 2 was obtained. The sensitivity of HD-dUGT2B10 to fenvalerate, deltamethrin, cyantraniliprole, acetamiprid, and lufenuron increased significantly, with sensitivity index increased 2.523-, 2.544-, 2.250-, 2.473-, and 3.556-fold, respectively. These results suggested that UGT2B10 was involved in the detoxification of H. armigera to insecticides mentioned above, shedding light upon further understanding of the detoxification mechanisms of insecticides by insect UGTs.

Insights into the Detoxification of Spruce Monoterpenes by the Eurasian Spruce Bark Beetle

Plant defence mechanisms, including physical barriers like toughened bark and chemical defences like allelochemicals, are essential for protecting them against pests. Trees allocate non-structural carbohydrates (NSCs) to produce secondary metabolites like monoterpenes, which increase during biotic stress to fend off pests like the Eurasian spruce bark beetle, ESBB (Ips typographus). Despite these defences, the ESBB infests Norway spruce, causing significant ecological damage by exploiting weakened trees and using pheromones for aggregation. However, the mechanism of sensing and resistance towards host allelochemicals in ESBB is poorly understood. We hypothesised that the exposure of ESBB to spruce allelochemicals, especially monoterpenes, leads to an upsurge in the important detoxification genes like P450s, GSTs, UGTs, and transporters, and at the same time, genes responsible for development must be compromised. The current study demonstrates that exposure to monoterpenes like R-limonene and sabiene effectively elevated detoxification enzyme activities. The differential gene expression (DGE) analysis revealed 294 differentially expressed (DE) detoxification genes in response to R-limonene and 426 DE detoxification genes in response to sabiene treatments, with 209 common genes between the treatments. Amongst these, genes from the cytochrome P450 family 4 and 6 genes (CP4 and CP6), esterases, glutathione S-transferases family 1 (GSTT1), UDP-glucuronosyltransferase 2B genes (UDB), and glucose synthesis-related dehydrogenases were highly upregulated. We further validated 19 genes using RT-qPCR. Additionally, we observed similar high expression levels of detoxification genes across different monoterpene treatments, including myrcene and α-pinene, suggesting a conserved detoxification mechanism in ESBB, which demands further investigation. These findings highlight the potential for molecular target-based beetle management strategies targeting these key detoxification genes.

UGT201H1 overexpression confers cyflumetofen resistance in Tetranychus cinnabarinus (Boisduval)

BACKGROUND

Tetranychus cinnabarinus is one of the most common polyphagous arthropod herbivores, and is primarily controlled by the application of acaricides. The heavy use of acaricides has led to high levels of resistance to acaricides such as cyflumetofen, which poses a threat to global resistance management programs. Cyflumetofen resistance is caused by an increase in metabolic detoxification; however, the role of uridine diphosphate (UDP)-glycosyltransferase (UGT) genes in cyflumetofen resistance remains to be determined.

RESULTS

Synergist 5-nitrouracil (5-Nul) significantly enhanced cyflumetofen toxicity in T. cinnabarinus, which indicated that UGTs are involved in the development of cyflumetofen resistance. Transcriptomic analysis and quantitative (q)PCR assays demonstrated that the UGT genes, especially UGT201H1, were highly expressed in the YN-CyR strain, compared to those of the YN-S strain. The RNA interference (RNAi)-mediated knockdown of UGT201H1 expression diminished the levels of cyflumetofen resistance in YN-CyR mites. The findings additionally revealed that the recombinant UGT201H1 protein plays a role in metabolizing cyflumetofen. Our results also suggested that the aromatic hydrocarbon receptor (AhR) probably regulates the overexpression of the UGT201H1 detoxification gene.

CONCLUSION

UGT201H1 is involved in cyflumetofen resistance, and AhR may regulates the overexpression of UGT201H1. These findings provide deeper insights into the molecular mechanisms underlying UGT-mediated metabolic resistance to chemical insecticides. © 2024 Society of Chemical Industry.

Differentiation in detoxification gene complements, including neofunctionalization of duplicated cytochrome P450 genes, between lineages of cotton bollworm, Helicoverpa armigera

Here we investigate the evolutionary dynamics of five enzyme superfamilies (CYPs, GSTs, UGTs, CCEs and ABCs) involved in detoxification in Helicoverpa armigera. The reference assembly for an African isolate of the major lineages, H. a. armigera, has 373 genes in the five superfamilies. Most of its CYPs, GSTs, UGTs and CCEs and a few of its ABCs occur in blocks and most of the clustered genes are in subfamilies specifically implicated in detoxification. Most of the genes have orthologues in the reference genome for the Oceania lineage, H. a. conferta. However, clustered orthologues and subfamilies specifically implicated in detoxification show greater sequence divergence and less constraint on non-synonymous differences between the two assemblies than do other members of the five superfamilies. Two duplicated CYPs, which were found in the H. a. armigera but not H. a. conferta reference genome, were also missing in 16 Chinese populations spanning two different lineages of H. a. armigera. The enzyme produced by one of these duplicates has higher activity against esfenvalerate than a previously described chimeric CYP mutant conferring pyrethroid resistance. Various transposable elements were found in the introns of most detoxification genes, generating diverse gene structures. Extensive resequencing data for the Chinese H. a. armigera and H. a. conferta lineages also revealed complex copy number polymorphisms in 17 CCE001s in a cluster also implicated in pyrethroid metabolism, with substantial haplotype differences between all three lineages. Our results suggest that cotton bollworm has a versatile complement of detoxification genes which are evolving in diverse ways across its range.

UDP-glycosyltransferases act as key determinants of host plant range in generalist and specialist Spodoptera species

Phytophagous insects have evolved sophisticated detoxification systems to overcome the antiherbivore chemical defenses produced by many plants. However, how these biotransformation systems differ in generalist and specialist insect species and their role in determining insect host plant range remains an open question. Here, we show that UDP-glucosyltransferases (UGTs) play a key role in determining the host range of insect species within the Spodoptera genus. Comparative genomic analyses of Spodoptera species that differ in host plant breadth identified a relatively conserved number of UGT genes in generalist species but high levels of UGT gene pseudogenization in the specialist Spodoptera picta. CRISPR-Cas9 knockouts of the three main UGT gene clusters of Spodoptera frugiperda revealed that UGT33 genes play an important role in allowing this species to utilize the poaceous plants maize, wheat, and rice, while UGT40 genes facilitate utilization of cotton. Further functional analyses in vivo and in vitro identified the UGT SfUGT33F32 as the key mechanism that allows generalist S. frugiperda to detoxify the benzoxazinoid DIMBOA (2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one), a potent insecticidal phytotoxin produced by poaceous plants. However, while this detoxification capacity is conserved in several generalist Spodoptera species, Spodoptera picta, which specializes on Crinum plants, is unable to detoxify DIMBOA due to a nonfunctionalizing mutation in SpUGT33F34. Collectively, these findings provide insight into the role of insect UGTs in host plant adaptation, the mechanistic basis of evolutionary transitions between generalism and specialism and offer molecular targets for controlling a group of notorious insect pests.

De Novo Genome Assembly and Annotation of Leptosia nina Provide New Insights into the Evolutionary Dynamics of Genes Involved in Host-Plant Adaptation of Pierinae Butterflies

In interactions between plants and herbivorous insects, the traits enabling phytophagous insects to overcome chemical defenses of their host plants have evolved multiple times. A prominent example of such adaptive key innovations in herbivorous insects is nitrile specifier proteins (NSPs) that enabled Pierinae butterflies to colonize Brassicales host plants that have a glucosinolate-myrosinase defense system. Although the evolutionary aspects of NSP-encoding genes have been studied in some Pierinae taxa (especially among Pieris butterflies), the ancestral evolutionary state of NSPs is unclear due to the limited genomic information available for species within Pierinae. Here, we generate a high-quality genome assembly and annotation of Leptosia nina, a member of a small tribe, Leptosiaini. L. nina uses as its main host Capparaceae plants, one of the ancestral hosts within Pierinae. By using ∼90-fold coverage of Oxford Nanopore long reads and Illumina short reads for subsequent polishing and error correction, we constructed a final genome assembly that consisted of 286 contigs with a total of 225.8 Mb and an N50 of 10.7 Mb. Genome annotation with transcriptome hints predicted 16,574 genes and covered 98.3% of BUSCO genes. A typical NSP gene is composed of three tandem domains found in Pierinae butterflies; unexpectedly, we found a new NSP-like gene in Pierinae composed of only two tandem domains. This newly found NSP-like gene in L. nina provides important insights into the evolutionary dynamics of domain and gene duplication events relating to host-plant adaptation in Pierinae butterflies.

Keap1 Negatively Regulates Transcription of Three Counter-Defense Genes and Susceptibility to Plant Toxin Gossypol in Helicoverpa armigera

Expressions of a wide range of cytoprotective counter-defense genes are mainly regulated by the Keap1-Nrf2-ARE signaling pathway in response to oxidative stress from xenobiotics. Gossypol is the major antiherbivore secondary metabolite of cotton, but how the polyphagous pest Helicoverpa armigera copes with this phytochemical to utilize its favorite host plant cotton remains largely elusive. In this study, we first suppressed the Keap1 gene in newly hatched larvae of cotton bollworm by feeding them the siRNA diet for 4 days. All of the larvae were subsequently fed the artificial diet supplied with gossypol or the control diet for 5 days. We identified that the knockdown of the Keap1 gene significantly decreased larval mortality and significantly increased the percentages of larval survival, reaching the fourth instar, compared with ncsiRNA when exposed to a diet containing gossypol. Three counter-defense genes CYP9A17, CYP4L11 and UGT41B3, which were related to the induction or metabolism of gossypol according to the report before, were all significantly up-regulated after the knockdown of the Keap1 gene. The Antioxidant Response Elements (AREs) were also detected in the promoter regions of the three counter-defense genes above. These data indicate that the suppression of the Keap1 gene activates the Keap1-Nrf2-ARE signaling pathway, up-regulates the expressions of counter-defense genes involved in the resistance of oxidative stress and finally contributes to reducing the susceptibility of gossypol. Our results provide more knowledge about the transcriptional regulation mechanisms of counter-defense genes that enable the cotton bollworm to adapt to the diversity of host plants including cotton.

CRISPR/Cas9-Based Functional Characterization of SfUGT50A15 Reveals Its Roles in the Resistance of Spodoptera frugiperda to Chlorantraniliprole, Emamectin Benzoate, and Benzoxazinoids

UDP-glycosyltransferases (UGTs) are a diverse superfamily of enzymes. Insects utilize uridine diphosphate-glucose (UDP-glucose) as a glycosyl donor for glycosylation in vivo, involved in the glycosylation of lipophilic endosymbionts and xenobiotics, including phytotoxins. UGTs act as second-stage detoxification metabolizing enzymes, which are essential for the detoxification metabolism of insecticides and benzoxazine compounds. However, the UGT genes responsible for specific glycosylation functions in S. frugiperda are unclear at present. In this study, we utilized CRISPR/Cas9 to produce a SfUGT50A15-KO strain to explore its possible function in governing sensitivity to chemical insecticides or benzoxazinoids. The bioassay results suggested that the SfUGT50A15-KO strain was significantly more sensitive to chlorantraniliprole, emamectin benzoate, and benzoxazinoids than the wild-type strains. This finding suggests that the overexpression of the SfUGT50A15 gene may be linked to S. frugiperda resistance to pesticides (chlorantraniliprole and emamectin benzoate) as well as benzoxazinoids (BXDs).

Uridine diphosphate glucosyltransferases are involved in spinosad resistance in western flower thrips Frankliniella occidentalis (Pergande)

Uridine diphosphate glucosyltransferases (UGTs) play crucial roles in the insect detoxification system and are associated with pesticide resistance. Our previous transcriptomic analysis of spinosad-susceptible (Ivf03) and resistant (NIL-R) Frankliniella occidentalis revealed numerous upregulated UGT genes in the NIL-R strain, suggesting their potential contribution to spinosad resistance. To investigate this hypothesis, here we conducted UGT activity assays and spinosad induction experiments, employing RNA interference (RNAi) techniques for gene function validation. We found significantly elevated UGT activity in the NIL-R strain compared to Ivf03, with 5-nitrouracil showing a substantial synergistic effect on the resistant strain. Eighteen UGT genes were identified in F. occidentalis, with gene expansion and duplication observed within families UGT466, 467, and 468. Ten out of the eighteen UGTs exhibited higher expression levels in NIL-R, specifically FoUGT466B1, FoUGT468A3, and FoUGT468A4 consistently being upregulated across nymphs, males, and females. RNAi-based functional validation targeting these three UGT genes led to increased susceptibility to spinosad in a life stage-, sex-, and dose-dependent manner. These results indicate that UGTs are indeed involved in spinosad resistance in F. occidentalis, and the effects are dependent on life stage, sex, and dose. Therefore, sustainable control for F. occidentalis resistance should always consider these differential responses.

Testing the selective sequestration hypothesis: Monarch butterflies preferentially sequester plant defences that are less toxic to themselves while maintaining potency to others

Herbivores that sequester toxins are thought to have cracked the code of plant defences. Nonetheless, coevolutionary theory predicts that plants should evolve toxic variants that also negatively impact specialists. We propose and test the selective sequestration hypothesis, that specialists preferentially sequester compounds that are less toxic to themselves while maintaining toxicity to enemies. Using chemically distinct plants, we show that monarch butterflies sequester only a subset of cardenolides from milkweed leaves that are less potent against their target enzyme (Na+ /K+ -ATPase) compared to several dominant cardenolides from leaves. However, sequestered compounds remain highly potent against sensitive Na+ /K+ -ATPases found in most predators. We confirmed this differential toxicity with mixtures of purified cardenolides from leaves and butterflies. The genetic basis of monarch adaptation to sequestered cardenolides was also confirmed with transgenic Drosophila that were CRISPR-edited with the monarch's Na+ /K+ -ATPase. Thus, the monarch's selective sequestration appears to reduce self-harm while maintaining protection from enemies.

Functional analysis of UDP-glycosyltransferase genes conferring indoxacarb resistance in Spodoptera litura

UDP-glycosyltransferase (UGT) is the major detoxification enzymes of phase II involved in xenobiotics metabolism, which potentially mediates the formation of insect resistance. Previous transcriptome sequencing studies have found that several UGT genes were upregulated in indoxacarb resistant strains of Spodoptera litura, but whether these UGT genes were involved in indoxacarb resistance and their functions in resistance were unclear. In this study, the UGTs inhibitor, 5-nitrouracil, enhanced the toxicity of indoxacarb against S. litura, preliminarily suggesting that UGTs were participated in indoxacarb resistance. Two UGT genes, UGT33J17 and UGT41D10 were upregulated in the resistant strains and could be induced by indoxacarb. Alignment of UGT protein sequences revealed two conserved donor-binding regions with several key residues that interact with catalytic sites and sugar donors. Further molecular modeling and docking analysis indicated that two UGT proteins were able to stably bind indoxacarb and N-decarbomethoxylated metabolite (DCJW). Furthermore, knockdown of UGT33J17 and UGT41D10 decreased viability of Spli-221 cells and enhanced susceptibility of larvae to indoxacarb. Transgenic overexpression of these genes reduced the toxicity of indoxacarb in Drosophila melanogaster. This work revealed that upregulation of UGT genes significantly contributes to indoxacarb resistance in S. litura, and is of great significance for the development of integrated and sustainable management strategies for resistant pests in the field.

Over-expression of UDP-glycosyltransferase UGT353G2 confers resistance to neonicotinoids in whitefly (Bemisia tabaci)

The whitefly, Bemisia tabaci, comes up high metabolic resistance to most neonicotinoids in long-term evolution, which is the key problem of pest control. UGT glycosyltransferase, as a secondary detoxification enzyme, plays an indispensable role in detoxification metabolism. In this study, UGT inhibitors, 5-nitrouracil and sulfinpyrazone, dramatically augmented the toxic damage of neonicotinoids to B. tabaci. A UGT named UGT353G2 was identified in whitefly, which was notably up-regulated in resistant strain (3.92 folds), and could be induced by most neonicotinoids. Additionally, the using of RNA interference (RNAi) suppresses UGT353G2 substantially increased sensitivity to neonicotinoids in resistant strain. Our results support that UGT353G2 may be involved in the neonicotinoids resistance of whitefly. These findings will help further verify the functional role of UGTs in neonicotinoid resistance.

Transcriptional regulation and overexpression of GST cluster enhances pesticide resistance in the cotton bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae)

The rapid evolution of resistance in agricultural pest poses a serious threat to global food security. However, the mechanisms of resistance through metabolic regulation are largely unknown. Here, we found that a GST gene cluster was strongly selected in North China (NTC) population, and it was significantly genetically-linked to lambda-cyhalothrin resistance. Knockout of the GST cluster using CRISPR/Cas9 significantly increased the sensitivity of the knockout strain to lambda-cyhalothrin. Haplotype analysis revealed no non-synonymous mutations or structural variations in the GST cluster, whereas GST_119 and GST_121 were significantly overexpressed in the NTC population. Silencing of GST_119 or co-silencing of GST_119 and GST_121 with RNAi significantly increased larval sensitivity to lambda-cyhalothrin. We also identified additional GATAe transcription factor binding sites in the promoter of NTC_GST_119. Transient expression of GATAe in Hi5 cells activated NTC_GST_119 and Xinjiang (XJ)_GST_119 transcription, but the transcriptional activity of NTC_GST_119 was significantly higher than that of XJ_GST_119. These results demonstrate that variations in the regulatory region result in complex expression changes in the GST cluster, which enhances lambda-cyhalothrin resistance in field-populations. This study deepens our knowledge of the evolutionary mechanism of pest adaptation under environmental stress and provides potential targets for monitoring pest resistance and integrated management.

Biodegradation of Gossypol by Aspergillus terreus-YJ01

Gossypol, generally found in the roots, stems, leaves, and, especially, the seeds of cotton plants, is highly toxic to animals and humans, which inhibits the use of cotton stalks as a feed resource. Here, a promising fungal strain for biodegrading gossypol was successfully isolated from the soil of cotton stalk piles in Xinjiang Province, China, and identified as Aspergillus terreus-YJ01 with the analysis of ITS. Initial gossypol of 250 mg·L-1 could be removed by 97% within 96 h by YJ01, and initial gossypol of 150 mg·L-1 could also be catalyzed by 98% or 99% within 36 h by the intracellular or extracellular crude enzymes of YJ01. Sucrose and sodium nitrate were found to be the optimal carbon and nitrogen sources for the growth of YJ01, and the optimal initial pH and inoculum size for the growth of YJ01 were 6.0 and 1%, respectively. To further elucidate the mechanisms underlying gossypol biodegradation by YJ01, the draft genome of YJ01 was sequenced using Illumina HiSeq, which is 31,566,870 bp in length with a GC content of 52.27% and a total of 9737 genes. Eight genes and enzymes were predicted to be involved in gossypol biodegradation. Among them, phosphoglycerate kinase, citrate synthase, and other enzymes are related to the energy supply process. With sufficient energy, β-1, 4-endo-xylanase may achieve the purpose of biodegrading gossypol. The findings of this study provide valuable insights into both the basic research and the application of A. terreus-YJ01 in the biodegradation of gossypol in cotton stalks.

UGT2B13 and UGT2C1 are involved in lambda-cyhalothrin resistance in Rhopalosiphum padi

Uridine diphosphate-glucuronosyltransferases (UGTs) are major multifunctional detoxification phase II enzymes involved in the metabolic detoxification of xenobiotics. However, their roles in insecticides resistance are still unclear. In this study, we identified two UGTs genes (UGT2B13 and UGT2C1) in Rhopalosiphum padi, a serious insect pest of wheat worldwide. Bioassays results showed that the resistance ratio of R. padi resistance strain (LC-R) to lambda-cyhalothrin (LC) was 2963.8 fold. The roles of UGT2B13 and UGT2C1 in lambda-cyhalothrin resistance were evaluated. Results indicated that the UGTs contents were significantly increased in the LC resistant strain of R. padi. UGT2B13 and UGT2C1 were significantly overexpressed in the LC-R strain. Transcription levels of UGT2B13 and UGT2C1 were relatively higher in the gut of LC-R strain. RNA interference (RNAi) of UGT2B13 or UGT2C1 significantly decreased the UGTs contents of the LC-R aphids and increased mortality of R. padi exposure to the LC50 concentration of LC. This study provides a new view that UGTs are involved in LC resistance of R. padi. The findings will promote further work to detailed the functions of UGTs in the metabolism resistance of insects to insecticides.

Non-volatile metabolites mediate plant interactions with insect herbivores

Non-volatile metabolites constitute the bulk of plant biomass. From the perspective of plant-insect interactions, these structurally diverse compounds include nutritious core metabolites and defensive specialized metabolites. In this review, we synthesize the current literature on multiple scales of plant-insect interactions mediated by non-volatile metabolites. At the molecular level, functional genetics studies have revealed a large collection of receptors targeting plant non-volatile metabolites in model insect species and agricultural pests. By contrast, examples of plant receptors of insect-derived molecules remain sparse. For insect herbivores, plant non-volatile metabolites function beyond the dichotomy of core metabolites, classed as nutrients, and specialized metabolites, classed as defensive compounds. Insect feeding tends to elicit evolutionarily conserved changes in plant specialized metabolism, whereas its effect on plant core metabolism varies widely based the interacting species. Finally, several recent studies have demonstrated that non-volatile metabolites can mediate tripartite communication on the community scale, facilitated by physical connections established through direct root-to-root communication, parasitic plants, arbuscular mycorrhizae and the rhizosphere microbiome. Recent advances in both plant and insect molecular biology will facilitate further research on the role of non-volatile metabolites in mediating plant-insect interactions.

Contribution of UDP-glycosyltransferases to chlorpyrifos resistance in Nilaparvata lugens

As a multigene superfamily of Phase II detoxification enzymes, uridine diphosphate (UDP)-glycosyltransferases (UGTs) play important roles in the metabolism of xenobiotics including insecticides. In this study, 5-nitrouracil, an inhibitor of UGT enzyme activity, effectively increased the toxicity of chlorpyrifos to the chlorpyrifos-resistant strain of Nilaparvata lugens, one of the most resistant rice pests. The enzyme content of UGT in the resistant strain was significantly higher than that in the susceptible strain. Among 20 identified UGT genes, UGT386H2, UGT386J2, UGT386N2 and UGT386P1 were found significantly overexpressed in the resistant strain and can be effectively induced by chlorpyrifos. These four UGT genes were most highly expressed in the midgut and/or fat body, two main insect detoxification tissues. Amino acid sequence alignments revealed that these four UGTs contained a variable N-terminal substrate-binding domain and a conserved C-terminal sugar donor-binding domain. Furthermore, homology modeling and molecular docking analyses showed that these UGTs could stably bind to chlorpyrifos and chlorpyrifos oxon, with the binding free energies from -19.4 to -110.62 kcal mol^-1. Knockdown of UGT386H2 or UGT386P1 by RNA interference dramatically increased the susceptibility of the resistant strain to chlorpyrifos. These findings suggest that overexpression of these two UGT genes contributes to chlorpyrifos resistance in N. lugens.

Identification and characterization of UDP-glycosyltransferase genes and the potential role in response to insecticides exposure in Bactrocera dorsalis

BACKGROUND

The oriental fruit fly, Bactrocera dorsalis (Hendel) is a worldwide pest damaging a wide range of hosts. Due to the long-term indiscriminate use of insecticides, B. dorsalis has developed serious resistance to several insecticides. UDP-glycosyltransferases (UGTs) are secondary metabolic enzymes involved in biotransformation and play an important role in the metabolism of plant secondary metabolites and synthetic insecticides in insects. Thus, we suspect that UGTs in B. dorsalis play an important role in insecticide tolerance.

RESULTS

In this study, 31 UGT genes were identified in the genome of B. dorsalis, belonging to 13 subfamilies. Real-time quantitative polymerase chain reaction (RT-qPCR) results revealed that 12 UGT genes were highly expressed in the antennae, midgut, Malpighian tubule and fat body. The mRNA expressions of 17 UGT genes were up-regulated upon exposure to λ-cyhalothrin, imidacloprid, abamectin and chlorpyrifos. Knockdown of the selected five UGT genes (BdUGT301D2, BdUGT35F2, BdUGT36K2, BdUGT49D2, BdUGT50B5) by RNA interference increased the mortality of B. dorsalis from 9.29% to 27.22% upon exposure to four insecticides.

CONCLUSION

The abundance of UGTs in B. dorsalis is similar to other insect species, and 12 out of 31 UGTs were specifically expressed in metabolic tissues, suggesting a key role in detoxification. Down-regulation of five selected UGT genes increased the susceptibility of B. dorsalis to various insecticides, indicating that UGTs may play an important role in tolerance of B. dorsalis to multiple insecticides. © 2022 Society of Chemical Industry.

Comparison of the efficacy of gossypol acetate enantiomers in rats with uterine leiomyoma

Gossypol acetate (GA), as the product of racemic gossypol and acetic acid conjugated by hydrogen bond, is hydrolyzed into gossypol to exert its effect on treating uterine leiomyoma (UL), which has been listed in China. But hypokalemia and mild changes of liver function limit its clinical application. It had been reported that the biological activities of gossypol optical isomers were different. In this study, we aimed to clarify whether there were differences in the efficacy of gossypol enantiomers and whether a single gossypol optical isomer could alleviate adverse reactions in the treatment of UL. The results indicated that (-)-GA and (+)-GA had significant therapeutic effect on rats with UL. Interestingly, (-)-GA could better significantly ameliorate the pathological structure, inhibit the secretion of estrogen, and downregulate the expression of estrogen receptor-alpha (ER-α) and progesterone receptor (PR) than (+)-GA. Additionally, (-)-GA could better evidently decrease the symptoms of abnormally elevated inflammatory factors caused by UL. In contrast, (-)-GA and (+)-GA had certain effects on potassium ion concentration in serum, liver and kidney function, and the effects of (+)-GA on liver function were more obvious than (-)-GA. These findings will be of great significance to the drug development of gossypol optical isomers.

Biodegradation of Free Gossypol by Helicoverpa armigera Carboxylesterase Expressed in Pichia pastoris

Gossypol is a polyphenolic toxic secondary metabolite derived from cotton. Free gossypol in cotton meal is remarkably harmful to animals. Furthermore, microbial degradation of gossypol produces metabolites that reduce feed quality. We adopted an enzymatic method to degrade free gossypol safely and effectively. We cloned the gene cce001a encoding carboxylesterase (CarE) into pPICZαA and transformed it into Pichia pastoris GS115. The target protein was successfully obtained, and CarE CCE001a could effectively degrade free gossypol with a degradation rate of 89%. When esterase was added, the exposed toxic groups of gossypol reacted with different amino acids and amines to form bound gossypol, generating substances with (M + H) m/z ratios of 560.15, 600.25, and 713.46. The molecular formula was C₂₇H₂₈O₁₃, C₃₄H₃₆N₂O₆, and C₄₇H₅₉N₃O₃. The observed instability of the hydroxyl groups caused the substitution and shedding of the group, forming a substance with m/z of 488.26 and molecular formula C₃₁H₃₆O₅. These properties render the CarE CCE001a a valid candidate for the detoxification of cotton meal. Furthermore, the findings help elucidate the degradation process of gossypol in vitro.

Metabolization and sequestration of plant specialized metabolites in insect herbivores: Current and emerging approaches

Herbivorous insects encounter diverse plant specialized metabolites (PSMs) in their diet, that have deterrent, anti-nutritional, or toxic properties. Understanding how they cope with PSMs is crucial to understand their biology, population dynamics, and evolution. This review summarizes current and emerging cutting-edge methods that can be used to characterize the metabolic fate of PSMs, from ingestion to excretion or sequestration. It further emphasizes a workflow that enables not only to study PSM metabolism at different scales, but also to tackle and validate the genetic and biochemical mechanisms involved in PSM resistance by herbivores. This review thus aims at facilitating research on PSM-mediated plant-herbivore interactions.

Transcriptional Dynamics Induced by Diapause Hormone in the Silkworm, Bombyx mori

Diapause is a form of dormancy that organisms use to adapt to extreme environments by exhibiting developmental arrest. In the silkworm, Bombyx mori, diapause is thought to be elicited by diapause hormone (DH) signaling, which consists of interactions between DH and the DH receptor (DHR). However, the steps downstream of the DH signaling pathway are largely unknown. In the present study, we directly injected synthesized DH into the female pupae of a multivoltine, non-diapausing strain at 36 h after pupation. We found that the mRNA level of DHR declined at 4 h and recovered at 12 h after the injection of DH. Thus, we sequenced the transcriptome of the ovaries at 4 h and 12 h after the injection of DH. We identified 60 and 221 differentially expressed genes at 4 h and 12 h after the injection, respectively. All DEGs were identified, relating to 20E-related genes, JH-related genes, cellular detoxification, ribosomal proteins, lipid metabolism, and epigenetic modifications. Eleven genes were selected from the above categories to verify the transcriptome data. The qRT-PCR and RNA-Seq expression patterns of the genes were consistent, which indicated the authenticity and reliability of the transcriptome data. This study dramatically expands upon our knowledge of gene expression variation at the early phase of DH release.

Jasmonic Acid-Treated Cotton Plant Leaves Impair Larvae Growth Performance, Activities of Detoxification Enzymes, and Insect Humoral Immunity of Cotton Bollworm

Enhancement of plant defense by exogenous elicitors is a promising tool for integrated pest management strategy. In the present study, cotton plants were treated with different concentrations (0, 0.01, 0.1, and 1.0 mM) of the natural plant defense elicitor, jasmonic acid (JA), and defense-related indicators in the plants were then determined. The cotton bollworm larvae were fed with JA-treated cotton leaves and larvae performances were discussed in terms of larvae relative growth rate (RGR), larval duration, pupal mass, humoral immunity, and activities of a target enzyme, three detoxification enzymes and two metabolic enzymes. Research results showed that JA treatment increased the contents of gossypol and H₂O₂, and decreased that of the total soluble carbohydrates, and 0.1 mM JA was more powerful in the induction of defense-related parameters. As a consequence, cotton bollworm larvae reared on JA-treated cotton leaves showed slower RGR, prolonged larvae duration, and decreased pupal mass. In addition, when larvae were fed with JA-treated cotton leaves, activities of phenoloxidae (an indicator of humoral immunity) and acetylcholinesterase (AchE, a target enzyme), alkaline phosphatases (ALP), acidic phosphatase (ACP), and three detoxification enzymes, carboxylesterase (CarE), glutathione S-transferase (GST), and cytochrome P450 (P450), were all reduced compared to the control. Taken together, the results suggest that JA can be an alternative agent for pest management by delaying insect growth and inhibiting immune defense and detoxification capacity of the cotton bollworm, which may reduce the use of synthetic pesticides.

Alternative transcript splicing regulates UDP-glucosyltransferase-catalyzed detoxification of DIMBOA in the fall armyworm (Spodoptera frugiperda)

Herbivorous insects often possess the ability to detoxify chemical defenses from their host plants. The fall armyworm (Spodoptera frugiperda), which feeds principally on maize, detoxifies the maize benzoxazinoid 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) by stereoselective re-glucosylation using a UDP-glucosyltransferase, SfUGT33F28. SfUGT33F28 activity is induced by feeding on a DIMBOA-containing diet, but how this induction is regulated is unknown. In the present work, we describe the alternative splicing of the SfUGT33F28 transcript. Variant transcripts are differentially expressed in response to DIMBOA, and this transcriptional response is mediated by an insect aryl hydrocarbon receptor. These variants have large deletions leading to the production of truncated proteins that have no intrinsic UGT activity with DIMBOA but interact with the full-length enzyme to raise or lower its activity. Therefore, the formation of SfUGT33F28 splice variants induces DIMBOA-conjugating UGT activity when DIMBOA is present in the insect diet and represses activity in the absence of this plant defense compound.

Proteomic profiling for ovarian development and azadirachtin exposure in Spodoptera litura during metamorphosis from pupae to adults

Azadirachtin is one of the most successful botanical pesticides in agricultural pest control. To build a repertoire of proteins and pathways in response to azadirachtin exposure during ovarian development, iTRAQ-based comparative proteomic was conducted. 1423 and 1686 proteins were identified as differentially accumulated proteins (DAPs) by comparing the protein abundance in adult ovary with that in pupal ovary under normal and azadirachtin exposure condition, respectively. Bioinformatics analysis indicated that pupae-to-adult transition requires proteins related to proteasome and branched chain amino acids (BCAAs) degradation for ovary development. Azadirachtin exposure strongly affected glycosylation-related pathway. And proteins related to vitamin B6 synthesis were necessary for ovary development under normal and AZA-exposure condition. RNAi assays confirmed the essential roles of DAPs related to glycosylation and vitamin B6 synthesis in moth growth and ovary development. The results enhance our understanding of the molecular regulatory network for ovary development and provide valuable resources for using AZA-responsive proteins to develop novel bio-rational insecticides.

Differential expression profiling of Oxycarenus laetus Kirby (Hemiptera: Lygaeidae) upon exposure to gossypol

BACKGROUND

Gossypium hirsutum seeds are rich in gossypol. In addition to its diverse beneficial properties, it is a known anti-fertility inducing agent in humans. Oxycarenus laetus feeds on the cottonseeds and yet its courtship, mating and reproduction is unaffected.

METHODS AND RESULTS

In this study, we performed a transcriptome profiling of O. laetus fed on Abutilon indicum (AB-no gossypol), G. hirsutum (GH-natural gossypol) and 1400 ppm commercial gossypol-soaked GH seeds (GHGO). Illumina NextSeq-500 paired-end 75 bp reads were generated and de novo assembled (48,214 genes) to identify the differentially expressed transcripts (DET) between the samples. Gene enrichment, KEGG pathway and cluster profiling of the DETs resulted in the identification of vital genes involved in the detoxification, pheromone biosynthesis, cuticle protein in the GHGO sample. Cyp4C1, Cyp6a13, Cyp6a14, Cyp4g15, Cyp4em8, Cyp303a1 were the detoxification related genes identified. Similarly, SDR dehydrogenase family 11 and fatty acid synthase in pheromone biosynthesis and cuticle proteins (RR1 and RR2) coding transcripts were found to be differentially expressed.

CONCLUSION

This is the first study to report the expression of genes induced by gossypol in O. laetus. Based on the findings from the DET analysis, we conclude that the detoxification related genes of gossypol treated samples were affected.

Identification and Characterization of UDP-Glycosyltransferase Genes in a Cerambycid Beetle, Pharsalia antennata Gahan, 1894 (Coleoptera: Cerambycidae)

The cerambycid beetle, Pharsalia antennata Gahan, 1894 (Coleoptera: Cerambycidae), is a wood-boring pest that spends most of its life cycle in the trunks or under the bark of trees. These distinctive biological characteristics make it likely that this beetle will encounter a number of plant defensive compounds, coupled with a broad range of host plants, possibly resulting in the overexpression or expansion of uridine diphosphate (UDP)-glycosyltransferase (UGT) genes. Here, we identified and characterized the UGT gene family in P. antennata through transcriptome data, sequence and phylogenetic analyses, and PCR and homology modeling approaches. In total, 59 transcripts encoding UGTs were identified, 34 of which harbored full-length sequences and shared high conservation with the UGTs of Anoplophora glabripennis. Of the 34 PantUGTs, only 31.78% amino acid identity was observed on average, but catalytic and sugar binding residues were highly conserved. Phylogenetic analyses revealed four Cerambycidae-specific clades, including 30 members from P. antennata. Combining the transcriptome and PCR data showed that PantUGTs had a wide tissue expression, and the majority of the genes were presented mainly in antennae or abdomens, suggesting their putative roles in olfaction and detoxification. This study provides, for the first time, information on the molecular and genetic basis of P. antennata, greatly enhancing our knowledge of the detoxification-related UGT gene family.

Gut Metagenomic Profiling of Gossypol Induced Oxycarenus laetus (Hemiptera: Lygaeidae) Reveals Gossypol Tolerating Bacterial Species

Oxycarenus laetus is a cotton pest that primarily feeds on seeds that are rich in gossypol. Though gossypol is toxic to general herbivores, O. laetus does not show such complications and instead grows and reproduces well on cotton plants compared to its other hosts. In this study, we have fed O. laetus with natural and induced gossypol-based diets to explore the difference in its gut microbiota. We performed NGS 16S rRNA amplicon sequencing on the Illumina MiSeq platform and analyzed the data using the QIIME2 pipeline supplemented with Greengenes and EZBioCloud reference databases. We also used culture-based methods to identify a few abundant gut bacteria present in O. laetus. Enterococcus faecalis, Wolbachia bourtzisii, Wolbachia pipientis, Corynebacterium glyciniphilum, Staphylococcus sciuri, and Kocuria rosea were some of the major species that formed the core gut microbiome of O. laetus. We have also observed that some species were present only in the sample with the highest concentration of gossypol, signifying that they might have the potential to degrade gossypol.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12088-021-00964-0.

Transcriptomic analysis of salivary gland and proteomic analysis of oral secretion in Helicoverpa armigera under cotton plant leaves, gossypol, and tannin stresses

Gossypol and tannin are involved in important chemical defense processes in cotton plants. In this study, we used transcriptomics and proteomics to explore the changes in salivary gland functional genes and oral secretion (OS) proteins after feeding with artificial diet (containing gossypols and tannins) and cotton plant leaves. We found that dietary cotton plant leaves, gossypols and tannins exerted adverse impacts on the genes that regulated the functions of peptidase, GTPase, glycosyl hydrolases in the salivary glands of the Helicoverpa armigera (H. armigera). However, GST, UGT, hydrolases, and lipase genes were up-regulated to participate in the detoxification and digestive of H. armigera. The oral secretory proteins of H. armigera were significantly inhibited under the stress of gossypol and tannin, such as enzyme activity, but some proteins (such as PZC71358.1) were up-regulated and involved in immune and digestive functions. The combined analysis of transcriptomics and metabolomics showed a weak correlation, and the genes and proteins involved were mainly in digestive enzyme activities. Our work clarifies the deleterious physiological impacts of gossypols and tannins on H. armigera and reveals the mechanism by which H. armigera effectively mitigate the phytotoxic effects through detoxification and immune systems.

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.

UDP-glycosyltransferases contribute to the tolerance of parasitoid wasps towards insecticides

Meteorus pulchricornis (Wesmael) (Hymenoptera: Braconidae) is a predominant endoparasitoid of lepidopteran pests in mulberry fields. Extensive application of insecticides puts natural enemies under threat. UDP-glycosyltransferases (UGTs), as important detoxification enzymes, potentially contribute to the detoxification of pesticides in insects. To investigate the roles of UGTs in the process of tolerance towards commonly used insecticides in M. pulchricornis, ten UGT genes were identified from the transcriptome database of M. pulchricornis. Seven UGT genes contained full-length ORFs and shared 47.12-78.28% identity with other homologous hymenopteran insects. qRT-PCR validation revealed that UGT genes can be induced by treatment of sublethal doses of phoxim, cypermethrin and chlorfenapyr, respectively, and these upregulations were depending on the time post insecticide treatments. To further explore the functions of UGT genes, three MpulUGT genes were singly knocked down, which resulted in the decline of UGT expression and significantly increased mortality of parasitoids under sublethal doses of insecticides exposure. This study revealed that UGTs in M. pulchricornis contributed to the tolerance towards insecticides and provided basic insight into the insecticide detoxification mechanism in parasitoid wasps.

Consumption of gossypol increases fatty acid-amino acid conjugates in the cotton pests Helicoverpa armigera and Heliothis virescens

Gossypol is a toxic sesquiterpene dimer produced by cotton plants which deters herbivory by insects and vertebrates. Two highly reactive aldehyde groups contribute to gossypol toxicity by cross-linking herbivore proteins. We identified another consequence of consuming gossypol in two insect pests of cotton: increased amounts of fatty acid-amino acid conjugates (FACs). Eight different FACs in the feces of larval Helicoverpa armigera and Heliothis virescens increased when larvae consumed artificial diet containing gossypol, but not a gossypol derivative lacking free aldehyde groups (SB-gossypol). FACs are produced by joining plant-derived fatty acids with amino acids of insect origin in the larval midgut tissue by an unknown conjugase, and translocated into the gut lumen by an unknown transporter. FACs are hydrolyzed back into fatty acids and amino acids by an aminoacylase (L-ACY-1) in the gut lumen. The equilibrium level of FACs in the lumen is determined by a balance between conjugation and hydrolysis, which may differ among species. When heterologously expressed, L-ACY-1 of H. armigera but not H. virescens was inhibited by gossypol; consistent with the excretion of more FACs in the feces by H. armigera. FACs are known to benefit the plant host by inducing anti-herbivore defensive responses, and have been hypothesized to benefit the herbivore by acting as a surfactant and increasing nitrogen uptake efficiency. Thus in addition to its direct toxic effects, gossypol may negatively impact insect nitrogen uptake efficiency and amplify the signal used by the plant to elicit release of volatile compounds that attract parasitoids.

Comparative analysis of the detoxification gene inventory of four major Spodoptera pest species in response to xenobiotics

The genus Spodoptera (Lepidoptera: Noctuidae) comprises some of the most polyphagous and destructive agricultural pests worldwide. The success of many species of this genus is due to their striking abilities to adapt to a broad range of host plants. Superfamilies of detoxification genes play a crucial role in the adaption to overcome plant defense mechanisms mediated by numerous secondary metabolites and toxins. Over the past decade, a substantial amount of expression data in Spodoptera larvae was produced for those genes in response to xenobiotics such as plant secondary metabolites, but also insecticide exposure. However, this information is scattered throughout the literature and in most cases does not allow to clearly identify candidate genes involved in host-plant adaptation and insecticide resistance. In the present review, we analyzed and compiled information on close to 600 pairs of inducers (xenobiotics) and induced genes from four main Spodoptera species: S. exigua, S. frugiperda, S. littoralis and S. litura. The cytochrome P450 monooxygenases (P450s; encoded by CYP genes) were the most upregulated detoxification genes across the literature for all four species. Most of the data was provided from studies on S. litura, followed by S. exigua, S. frugiperda and S. littoralis. We examined whether these detoxification genes were reported for larval survival under xenobiotic challenge in forward and reverse genetic studies. We further analyzed whether biochemical assays were carried out showing the ability of corresponding enzymes and transporters to breakdown and excrete xenobiotics, respectively. This revealed a clear disparity between species and the lack of genetic and biochemical information in S. frugiperda. Finally, we discussed the biological importance of detoxification genes for this genus and propose a workflow to study the involvement of these enzymes in an ecological and agricultural context.

Gossypol detoxification in the rumen and Helicoverpa armigera larvae: A review

Gossypol, a phenolic compound found in the cotton plant, is widely distributed in cottonseed by-products. Although ruminant animals are believed to be more tolerant of gossypol toxicity than monogastric animals due to rumen microbial fermentation, the actual mechanisms of detoxification remain unclear. In contrast, the metabolic detoxification of gossypol by Helicoverpa armigera (Lepidoptera: Noctuidae) larvae has achieved great advances. The present review discusses the clinical signs of gossypol in ruminant animals, as well as summarizing advances in the study of gossypol detoxification in the rumen. It also examines the regulatory roles of several key enzymes in gossypol detoxification and transformation known in H. armigera. With the rapid development of modern molecular biotechnology and -omics technology strategies, evidence increasingly indicates that research into the biological degradation of gossypol in H. armigera larvae and some microbes, in terms of these key enzymes, could provide scientific insights that would underpin future work on microbial gossypol detoxification in the rumen, with the ultimate aim of further alleviating gossypol toxicity in ruminant animals.

Transcriptome analysis and response of three important detoxifying enzymes to Serratia marcescens Bizio (SM1) in Hyphantria cunea (Drury) (Lepidoptera: Noctuidae)

Hyphantria cunea (Drury) (Lepidoptera: Noctuidae) is a main pest of forest trees. In this study, the effects of Serratia marcescens Bizio (SM1) infection on the transcriptome of H. cunea were studied. The expression of 1068 unigenes in the transcriptome of H. cunea infected by S. marcescens was markedly different from that in the control of H. cunea; 474 genes were upregulated, and 594 genes were downregulated in the former. Among them, 8 cytochrome P450s (CYPs), 5 uridine diphosphate-glycosyltransferases (UGTs) and 3 glutathione S-transferases (GSTs) were significantly differentially expressed. Pathway enrichment analysis indicated that these differentially expressed detoxification enzyme genes were mainly involved in the drug metabolism pathway, glutathione metabolism pathway and ABC transporter pathway. Interestingly, we found that five UGTs were related to oestradiol metabolism in the steroid hormone biosynthesis pathway. Furthermore, the real-time fluorescent quantitative PCR results showed that SM1 could induce the expression of CYPs and UGTs, but inhibit the expression of GSTs. This research will identify the response of important detoxification enzymes to S. marcescens, which will provide a theoretical foundation for the development of new immunosuppressants for H. cunea control. Furthermore, H. cunea was performed transcriptome sequencing to explore the key metabolic pathways, signalling pathways and genes affected by S. marcescens, which will clarify the mechanisms of S. marcescens infection of H. cunea. In addition, this study also explored the relationship between H. cunea and S. marcescens, which will provide a theoretical basis for the biological control of H. cunea by using S. marcescens.

UDP-Glucosyltransferases Induced by Nosema bombycis Provide Resistance to Microsporidia in Silkworm (Bombyx mori)

Simple Summary

Nosema bombycis (N. bombycis), an obligate intracellular eukaryotic parasite, is a virulent pathogen of the silkworm, that causes major economic losses. Although many studies have reported on B. mori host response to this pathogen, little is known about which genes are induced by N. bombycis. Our results showed that two B. mori uridine diphosphate-glucosyltransferases (UGTs) (BmUGT10295 and BmUGT8453) could be activated by N. bombycis and provide resistance to the microsporidia in silkworms. These results will contribute to our understanding of host stress reaction to pathogens and the two pathogen-induced resistant genes will provide a target for promoting pathogen resistance.

Abstract

As a silkworm pathogen, the microsporidian N. bombycis can be transovarially transmitted from parent to offspring and seriously impedes sericulture industry development. Previous studies found that Uridine diphosphate (UDP)-glycosyltransferases (UGTs) are involved in regulating diverse cellular processes, such as detoxification, pigmentation, and odorant sensing. Our results showed that BmUGT10295 and BmUGT8453 genes were specifically induced in infected silkworms, but other BmUGTs were not. Tissue distribution analysis of the two BmUGTs showed that the transcriptions of the two BmUGTs were mainly activated in the midgut and Malpighian tubule of infected silkworms. Furthermore, there were significantly fewer microsporidia in over-expressed BmUGTs compared with the control, but there were significantly more microsporidia in RNA interference BmUGTs compared with the control. These findings indicate that the two BmUGTs were induced by N. bombycis and provided resistance to the microsporidia.

Dual oxidase-dependent reactive oxygen species are involved in the regulation of UGT overexpression-mediated clothianidin resistance in the brown planthopper, Nilaparvata lugens

BACKGROUND

Uridine diphosphate-glycosyltransferases (UGTs) are phase II metabolic enzymes involved in metabolism of toxins and resistance to insecticides in insect pests. Reactive oxygen species (ROS) induced by xenobiotics are important for activation of detoxification pathways. However, relationships between ROS and UGTs involved in toxin metabolism and insecticide resistance remain unclear.

RESULTS

Here, involvement of dual oxidase (Duox)-dependent ROS in regulating UGT expression-mediated insecticide resistance in the brown planthopper (Nilaparvata lugens) was investigated. The overexpression of NlUGT386F2 contributed to the resistance of N. lugens to clothianidin. Furthermore, the ROS inhibitor (N-acetylcysteine) significantly reduced the expression of NlUGT386F2 and increased the susceptibility of N. lugens to clothianidin. Silencing the ROS producer Duox significantly increased the susceptibility of N. lugens to clothianidin through the down-regulation of NlUGT386F2 expression.

CONCLUSION

NlDuox-dependent ROS regulates NlUGT386F2 expression-mediated clothianidin resistance in brown planthopper. These observations further our understanding of the metabolism of toxins and of insecticide-resistance in insect pests.