A novel role of Drosophila cytochrome P450-4e3 in permethrin insecticide tolerance

Time-series analysis of transcriptomic changes due to permethrin exposure reveals that Aedes aegypti undergoes detoxification metabolism over 24 h

Insecticide resistance is a multifaceted response and an issue across taxa. Aedes aegypti, the mosquito that vectors Zika, dengue, chikungunya, and yellow fever, demonstrates high levels of pyrethroid resistance across the globe, presenting a challenge to public health officials. To examine the transcriptomic shifts across time after exposure to permethrin, a 3'Tag-Seq analysis was employed on samples 6, 10, and 24 h after exposure along with controls. Differential expression analysis revealed significant shifts in detoxifying enzymes and various energy-producing metabolic processes. These findings indicate significant alterations in gene expression associated with key energy mobilization pathways within the system. These changes encompass a coordinated response involving lipolysis, beta-oxidation, and the citric acid cycle, required for the production of energetic molecules such as ATP, NADH, NADPH, and FADH. These findings highlight a complex interplay of metabolic processes that may have broader implications for understanding insect physiology and response to environmental stimuli. Among the upregulated detoxifying enzymes are cytochrome P450s, glutathione s-transferases and peroxidases, and ATP-binding cassette transporters. Additionally, eight heat shock genes or genes with heat shock domains exhibit the highest fold change across time. Twenty-four hours after exposure, samples indicate a global downregulation of these processes, though principal component analysis suggests lasting signatures of the response. Understanding the recovery response to insecticide exposure provides information on possible new genetic and synergist targets to explore.

Compromised junctional integrity phenocopies age-dependent renal dysfunction in Drosophila Snakeskin mutants

Transporting epithelia provide a protective barrier against pathogenic insults while allowing the controlled exchange of ions, solutes and water with the external environment. In invertebrates, these functions depend on formation and maintenance of 'tight' septate junctions (SJs). However, the mechanism by which SJs affect transport competence and tissue homeostasis, and how these are modulated by ageing, remain incompletely understood. Here, we demonstrate that the Drosophila renal (Malpighian) tubules undergo an age-dependent decline in secretory capacity, which correlates with mislocalisation of SJ proteins and progressive degeneration in cellular morphology and tissue homeostasis. Acute loss of the SJ protein Snakeskin in adult tubules induced progressive changes in cellular and tissue architecture, including altered expression and localisation of junctional proteins with concomitant loss of cell polarity and barrier integrity, demonstrating that compromised junctional integrity is sufficient to replicate these ageing-related phenotypes. Taken together, our work demonstrates a crucial link between epithelial barrier integrity, tubule transport competence, renal homeostasis and organismal viability, as well as providing novel insights into the mechanisms underpinning ageing and renal disease.

Identification and Functional Characterization of CYP4D2 Putatively Associated with β-Cypermethrin Detoxification in Phortica okadai

Phortica okadai, a polyphagous pest, serves as a vector for Thelazia callipaeda in China. Currently, there are no effective control strategies for this vector. Agricultural pest control may cause P. okadai to become a threat due to the development of pesticide resistance. Cytochrome P450s (CYP450) plays a significant role in detoxifying xenobiotics in insects. In this study, we performed RNA sequencing of P. okadai exposed to β-cypermethrin for 0 and 1 h and then gene cloning of the five up-regulated CYP450 genes. Three CYP450 genes were successfully cloned, and their expression patterns in different developmental stages and in different tissues were analyzed by RT-qPCR. Pocyp4d2 was observed to have the highest expression in the midgut (fold change 2.82 for Pocyp4d2, 2.62 for Pocyp49a1, and 1.77 for Pocyp28d2). Functional analysis was carried out according to overexpression in S2 cells from the pfastbac1 vector and RNAi with siRNA. The results of the CCK8 assay indicated that the overexpression of the recombinant protein PoCYP4D2 suppressed the decrease in S2 cell viability due to β-cypermethrin. The expression levels of PoCYP4D2 decreased significantly, and the mortality rates increased from 6.25% to 15.0% at 3 h and from 15.0% to 27.5% at 6 h after Pocyp4d2-siRNA injection. These results suggest that Pocyp4d2 may be an essential key gene in the metabolism of β-cypermethrin in P. okadai. This study constitutes a foundation to explore further the functions of P. okadai CYP450 genes in insecticide metabolism.

Fipronil exposure compromises respiration and damages the Malpighian tubules of the stingless bee Partamona helleri Friese (Hymenoptera: Apidae)

Fipronil has been widely used in agriculture and forestry in Brazil to control several pests. However, this insecticide may be hazardous to non-target organisms, including stingless bees, which are essential pollinators of crops and natural environments. Here, we investigated the effect of 24-h acute oral exposure to LC₅₀ of fipronil on the Malpighian tubules of the stingless bee Partamona helleri (Friese). Insecticide exposure decreases the respiration rate of forager bees, and the Malpighian tubules are severely affected, as shown by the epithelial architecture disorganization, loss of cytoplasmic content, degradation of the brush border, and nuclear pyknosis. In addition, fipronil ingestion increases the number of Malpighian cells positive for peroxidase, LC3, cleaved caspase-3, and JNK. However, Notch and ERK1/2-positive cells decrease in the exposed bees. These changes in the signaling proteins indicate an increase in oxidative stress, autophagy and apoptosis, and impairment of cell recovery. Overall, our results demonstrate the toxicological effects of fipronil on a stingless bee, which compromises the physiology of this important pollinator.

Multiple Functions of Malpighian Tubules in Insects: A Review

The Malpighian Tubules (MTs) are the main excretory organs in most insects. They play a key role in the production of primary urine and osmoregulation, selectively reabsorbing water, ions, and solutes. Besides these functions conserved in most insects, MTs can serve some specialized tasks at different stages of some species' development. The specialized functions include the synthesis of mucopolysaccharides and proteins for the building of foam nests, mucofibrils for the construction of dwelling tubes, adhesive secretions to help the locomotion, and brochosomes for protection as well as the usage of inorganic salts to harden the puparia, eggs chorion, and pupal cells' closing lids. MTs are also the organs responsible for the astonishing bioluminescence of some Diptera glowworms and can go through some drastic histological changes to produce a silk-like fiber utilized to spin cocoons. The specialized functions are associated with modifications of cells within the entire tubules, in specific segments, or, more rarely, modified secretory cells scattered along the MTs. In this review, we attempted to summarize the observations and experiments made over more than a century concerning the non-excretive functions of insects' MTs, underlying the need for new investigations supported by the current, advanced technologies available to validate outdated theories and clarify some dubious aspects.

Overexpression of Multiple Cytochrome P450 Genes Conferring Clothianidin Resistance in Bradysia odoriphaga

Cytochrome P450 monooxygenases (P450s) play important roles in the detoxification metabolism of xenobiotics and are involved in the resistance of insects to many insecticides. In this study, piperonyl butoxide (PBO), an inhibitor of P450 enzyme activity, significantly increased the toxicity of clothianidin in the clothianidin-resistant (CL-R) population of Bradysia odoriphaga. The enzyme activity of P450 in the CL-R population was significantly higher than that in the SS population. Furthermore, four P450 genes were found to be significantly overexpressed in the CL-R population. Tissue-specific expression analysis indicates that CYP9J57, CYP3828A1, CYP6SX1, and CYP6QE1 were most highly expressed in the midgut and/or Malpighian tubules. After exposure to LC₃₀ of clothianidin, the expression levels of the four P450 genes were significantly upregulated. The RNAi-mediated knockdown of CYP9J57, CYP3828A1, and CYP6QE1 significantly increased the susceptibility of B. odoriphaga to clothianidin. These results suggest that P450 genes are involved in clothianidin resistance in B. odoriphaga. This provides a better understanding of P450-mediated clothianidin resistance in B. odoriphaga and will contribute to the management of insect resistance to insecticides.

Monarda didyma Hydrolate Affects the Survival and the Behaviour of Drosophila suzukii

Simple Summary

During the steam distillation of aromatic plants, two main fractions are usually obtained: the hydrophobic essential oils and the hydrophilic fraction commonly known as hydrolate (HY). The essential oils are largely used in several industry fields, including the agricultural industry as biopesticides. Residual HYs, instead, are often discarded as by-products of little or no value. Our research pointed out that also HYs have biological activity, suggesting their potential use in plant-based strategy for the pest control. In more detail, we investigated the insecticidal properties of the hydrolate from Monarda didyma, scarlet beebalm, towards Drosophila suzukii. Using specific molecular and behavioural assays, we showed that M. didyma hydrolate affected the fitness and behaviour of D. suzukii, providing new insights in the D. suzukii control strategies through M. didyma hydrolate.

Abstract

Drosophila suzukii (Matsumara) is an herbivorous pest whose control in the field with conventional chemical is particularly difficult and has important drawbacks. Here, we investigated the insecticidal properties of hydrolate from Monarda didyma, scarlet beebalm, an aromatic herb in the Lamiaceae family. The identification of volatile organic compounds (VOCs) by CG–MS systems revealed that thymol (38%) and carvacrol (59%) were the most abundant VOCs in the hydrolate. M. didyma hydrolate did not show fumigant toxicity. Conversely, in contact assays, M. didyma hydrolate showed a LC₅₀ of 5.03 µL mL⁻¹, 48 h after the application on D. suzukii adults. Expression of detoxification genes increased in flies that survived the LC₅₀ application. Furthermore, toxicity persisted for 7 days after the treatment in the survival evaluation. Artificial diet assays with 100 and 1000 µL mL⁻¹ of M. didyma hydrolate resulted in a significant decrease in total food intake in both male and female D. suzukii adults. In addition, electropenetrography (EPG) showed that the D. suzukii females’ feeding behaviour was altered in hydrolate-treated diets. The hydrolate also caused a significant reduction in the number of eggs laid in two different oviposition assays. Overall, our findings provide a new perspective for the improvement of D. suzukii control strategies through M. didyma hydrolate.

Possible enzymatic mechanism underlying chemical tolerance and characteristics of tolerant population in Scapholeberis kingi

To determine the potential effects of pesticides on aquatic organisms inhabiting a realistic environment, we explored the characteristics and mechanisms of chemical tolerance in Scapholeberis kingi(Cladocera). We established a chemical-tolerant population via continuous exposure to pirimicarb, an acetylcholinesterase (AChE) inhibitor, and examined the effects of pirimicarb concentration on the intrinsic growth rates (r) of tolerant cladocerans. We also explored the association between r and feeding rate and tested the involvement of antioxidant enzymes [peroxidase (PO) and superoxide dismutase] and AChE in pirimicarb sensitivity. S. kingi was continuously exposed to lethal and sublethal pirimicarb concentrations (0, 2.5, 5, and 10 µg/L) for 15 generations, and changes (half maximal effective concentration at 48 h, 48 h-EC₅₀) in chemical sensitivity were investigated. In the F14 generation, the sensitivity of the 10 µg/L group was three times lower than that of the control group, suggesting the acquisition of chemical tolerance. Moreover, r was significantly and negatively correlated with 48 h-EC₅₀, suggesting a fitness cost for tolerance. Surprisingly, there was no significant correlation between r and feeding rate. There was a weak but significant positive correlation between each enzyme activity and the 48 h-EC₅₀ value (p < 0.05). Thus, oxidative stress regulation and enhanced AChE may be involved in the acquisition of chemical tolerance in cladocerans. These findings will help elucidate the characteristics and mechanisms of chemical tolerance in aquatic organisms.

Low doses of the organic insecticide spinosad trigger lysosomal defects, elevated ROS, lipid dysregulation, and neurodegeneration in flies

Large-scale insecticide application is a primary weapon in the control of insect pests in agriculture. However, a growing body of evidence indicates that it is contributing to the global decline in population sizes of many beneficial insect species. Spinosad emerged as an organic alternative to synthetic insecticides and is considered less harmful to beneficial insects, yet its mode of action remains unclear. Using Drosophila, we show that low doses of spinosad antagonize its neuronal target, the nicotinic acetylcholine receptor subunit alpha 6 (nAChRα6), reducing the cholinergic response. We show that the nAChRα6 receptors are transported to lysosomes that become enlarged and increase in number upon low doses of spinosad treatment. Lysosomal dysfunction is associated with mitochondrial stress and elevated levels of reactive oxygen species (ROS) in the central nervous system where nAChRα6 is broadly expressed. ROS disturb lipid storage in metabolic tissues in an nAChRα6-dependent manner. Spinosad toxicity is ameliorated with the antioxidant N-acetylcysteine amide. Chronic exposure of adult virgin females to low doses of spinosad leads to mitochondrial defects, severe neurodegeneration, and blindness. These deleterious effects of low-dose exposures warrant rigorous investigation of its impacts on beneficial insects.

Origin and Development of the Adipose Tissue, a Key Organ in Physiology and Disease

Adipose tissue is a dynamic organ, well known for its function in energy storage and mobilization according to nutrient availability and body needs, in charge of keeping the energetic balance of the organism. During the last decades, adipose tissue has emerged as the largest endocrine organ in the human body, being able to secrete hormones as well as inflammatory molecules and having an important impact in multiple processes such as adipogenesis, metabolism and chronic inflammation. However, the cellular progenitors, development, homeostasis and metabolism of the different types of adipose tissue are not fully known. During the last decade, Drosophila melanogaster has demonstrated to be an excellent model to tackle some of the open questions in the field of metabolism and development of endocrine/metabolic organs. Discoveries ranged from new hormones regulating obesity to subcellular mechanisms that regulate lipogenesis and lipolysis. Here, we review the available evidences on the development, types and functions of adipose tissue in Drosophila and identify some gaps for future research. This may help to understand the cellular and molecular mechanism underlying the pathophysiology of this fascinating key tissue, contributing to establish this organ as a therapeutic target.

Age-Related Changes of Gene Expression Profiles in Drosophila

An individual’s gene expression profile changes throughout their life. This change in gene expression is shaped by differences in physiological needs and functions between the younger and older organism. Despite intensive studies, the aging process is not fully understood, and several genes involved in this process may remain to be identified. Here we report a transcriptomic analysis of Drosophila melanogaster using microarrays. We compared the expression profiles of two-day-old female adult flies with those of 45-day-old flies. We identified 1184 genes with pronounced differences in expression level between young and old age groups. Most genes involved in muscle development/maintenance that display different levels of expression with age were downregulated in older flies. Many of these genes contributed to sarcomere formation and function. Several of these genes were functionally related to direct and indirect flight muscles; some of them were exclusively expressed in these muscles. Conversely, several genes involved in apoptosis processes were upregulated in aging flies. In addition, several genes involved in resistance to toxic chemicals were upregulated in aging flies, which is consistent with a global upregulation of the defense response system in aging flies. Finally, we randomly selected 12 genes among 232 genes with unknown function and generated transgenic flies expressing recombinant proteins fused with GFP protein to determine their subcellular expression. We also found that the knockdown of some of those 12 genes can affect the lifespan of flies.

Integrated transcriptome sequencing and RNA interference reveals molecular changes in Diaphorina citri after exposure to validamycin

Validamycin has been widely used as a specific competitive inhibitor of trehalase. In our previous research, validamycin significantly inhibited trehalase activity and chitin synthesis in Diaphorina citri, resulting in abnormal phenotypes. However, the mechanism of validamycin's action on D. citri remains unclear. Here, using a comparative transcriptome analysis, 464 differentially expressed genes (DEGs) in D. citri were identified after validamycin treatment. A Gene Ontology enrichment analysis revealed that these DEGs were mainly involved in "small molecule process", "structural molecule activity" and "transition metal ion binding". DEGs involved in chitin metabolism, cuticle synthesis and insecticide detoxification were validated by reverse transcription quantitative polymerase chain reaction. The RNA interference of D. citri chitinase-like protein ENO3 and D. citri cuticle protein 7 genes significantly affected D. citri molting. Moreover, the recombinant chitinase-like protein ENO3 exhibited a chitin-binding property, and an antimicrobial activity against Bacillus subtilis. This study provides a first insight into the molecular changes in D. citri after exposure to validamycin and identifies two effective RNA interference targets for D. citri control.

Inductions of a CYP6 cluster conferring deltamethrin resistance in colonized and field-collected Culex pipiens pallens

Mosquitoes transmit many damaging vector-borne diseases. Unfortunately, the rise of insecticide resistance has become a major obstacle to mosquito control. A preliminary study showed that a CYP6 cluster is significant for deltamethrin resistance in colonized Culex pipiens pallens. Here, several field strains were collected to explore the association of the cluster in deltamethrin tolerance. We examined the effect of deltamethrin treatment on the cluster expression at a deltamethrin concentration of LC₅₀ in these strains using five time points. As a result, both P450 induction and constitutive overexpression were associated with deltamethrin resistance. Deltamethrin could stimulate different expression sets in the P450 cluster in different strains, predominately correlated with the resistance level of the strain. Our results will offer more insight into working with the characterization of P450s related to insecticide resistance.

Molecular characterization of a catalase gene from the green peach aphid (Myzus persicae)

The green peach aphid, Myzus persicae (Sulzer), is a serious agricultural pest with a worldwide distribution. Catalase (CAT), which is encoded by the catalase (Cat) gene, is an extremely important antioxidant enzyme that plays a pivotal role in protecting cells against the toxic effects of hydrogen peroxide. The Cat gene has not been characterized in M. persicae; therefore, this study describes the identification of the Cat (MpCat) gene from M. persicae. MpCat contains an open reading frame of 1515 bp and encodes a MpCAT protein consisting of 504 amino-acid residues. MpCAT possesses features typical of other insect catalases, including 7 conserved amino acids involved in binding heme and 15 involved in binding nicotinamide adenine dinucleotide phosphate. Phylogenetic analysis showed that MpCAT was closely related to orthologs from other aphid species. MpCat consisted of nine exons and eight introns, and the number and insertion sites of introns are consistent with those of Cat genes from Acyrthosiphon pisum (Harris) and Aphis gossypii Glover. The mRNA transcripts of MpCat were detected at all tested developmental stages, with the highest mRNA level in alate adults. The expression of MpCat was significantly upregulated when M. persicae was exposed to low and high temperatures, ultraviolet radiation, Beauveria bassiana, and permethrin. The transcription of MpCat and the activity of catalase were suppressed by RNA interference, and knockdown of MpCat significantly reduced the survival rate in M. persicae under heat stress. The results provide valuable information for further study on the physiological functions of MpCat.

Drosophila models to study causative genes for human rare intractable neurological diseases

Drosophila is emerging as a convenient model for investigating human diseases. Functional homologues of almost 75% of human disease-related genes are found in Drosophila. Amyotrophic lateral sclerosis (ALS) is a severe neurodegenerative disease that causes defects in motoneurons. Charcot-Marie-Tooth disease (CMT) is one of the most commonly found inherited neuropathies affecting both motor and sensory neurons. No effective therapy has been established for either of these diseases. In this review, after overviewing ALS, Drosophila models targeting several ALS-causing genes, including TDP-43, FUS and Ubiquilin2, are described with their genetic interactants. Then, after overviewing CMT, examples of Drosophila models targeting several CMT-causing genes, including mitochondria-related genes and FIG 4, are also described with their genetic interactants. In addition, we introduce Sotos syndrome caused by mutations in the epigenetic regulator gene NSD1. Lastly, several genes and pathways that commonly interact with ALS- and/or CMT-causing genes are described. In the case of ALS and CMT that have many causative genes, it may be not practical to perform gene therapy for each of the many disease-causing genes. The possible uses of the common genes and pathways as novel diagnosis markers and effective therapeutic targets are discussed.

Aedes aegypti miRNA-33 modulates permethrin induced toxicity by regulating VGSC transcripts

Aedes aegypti is a major vector of Zika, dengue, and other arboviruses. Permethrin adulticidal spraying, which targets the voltage-gated sodium channel (VGSC), is commonly done to reduce local mosquito populations and protect humans from exposure to arbovirus pathogens transmitted by this dangerous pest. Permethrin resistance, however, is a growing problem and understanding its underlying molecular basis may identify avenues to combat it. We identified a single G:C polymorphism in pre-miR-33 that was genetically associated with permethrin resistance; resulting isoforms had structural differences that may affect DICER-1/pre-miRNA processing rates. We then assessed the effects of overexpression of pre-miR-33 isoforms on permethrin toxicological phenotypes, VGSC transcript abundance and protein levels for two genetically related mosquito strains. One strain had its naturally high permethrin resistance levels maintained by periodic treatment, and the other was released from selection. VGSC protein levels were lower in the permethrin resistant strain than in the related permethrin-susceptible strain. Overexpression of the G-pre-miR-33 isoform reduced VGSC expression levels in both strains. To further elucidate changes in gene expression associated with permethrin resistance, exome-capture gDNA deep sequencing, genetic association mapping and subsequent gene set enrichment analysis revealed that transport genes, in particular, were selected in resistant versus susceptible mosquitoes. Collectively, these data indicate that miR-33 regulates VGSC expression as part of a nuanced system of neuronal regulation that contributes to a network of heritable features determining permethrin resistance.

From Global to Local-New Insights into Features of Pyrethroid Detoxification in Vector Mosquitoes

The threat of mosquito-borne diseases continues to be a problem for public health in subtropical and tropical regions of the world; in response, there has been increased use of adulticidal insecticides, such as pyrethroids, in human habitation areas over the last thirty years. As a result, the prevalence of pyrethroid-resistant genetic markers in natural mosquito populations has increased at an alarming rate. This review details recent advances in the understanding of specific mechanisms associated with pyrethroid resistance, with emphasis on features of insecticide detoxification and the interdependence of multiple cellular pathways. Together, these advances add important context to the understanding of the processes that are selected in resistant mosquitoes. Specifically, before pyrethroids bind to their targets on motoneurons, they must first permeate the outer cuticle and diffuse to inner tissues. Resistant mosquitoes have evolved detoxification mechanisms that rely on cytochrome P450s (CYP), esterases, carboxyesterases, and other oxidation/reduction (redox) components to effectively detoxify pyrethroids to nontoxic breakdown products that are then excreted. Enhanced resistance mechanisms have evolved to include alteration of gene copy number, transcriptional and post-transcriptional regulation of gene expression, as well as changes to cellular signaling mechanisms. Here, we outline the variety of ways in which detoxification has been selected in various mosquito populations, as well as key gene categories involved. Pathways associated with potential new genes of interest are proposed. Consideration of multiple cellular pathways could provide opportunities for development of new insecticides.

Poly(ADP-ribose) polymerase 1 in genome-wide expression control in Drosophila

Poly(ADP-ribose) polymerase 1 (PARP-1) is a nuclear enzyme involved in DNA repair and transcription regulation, among other processes. Malignant transformations, tumor progression, the onset of some neuropathies and other disorders have been linked to misregulation of PARP-1 activity. Despite intensive studies during the last few decades, the role of PARP-1 in transcription regulation is still not well understood. In this study, a transcriptomic analysis in Drosophila melanogaster third instar larvae was carried out. A total of 602 genes were identified, showing large-scale changes in their expression levels in the absence of PARP-1 in vivo. Among these genes, several functional gene groups were present, including transcription factors and cytochrome family members. The transcription levels of genes from the same functional group were affected by the absence of PARP-1 in a similar manner. In the absence of PARP-1, all misregulated genes coding for transcription factors were downregulated, whereas all genes coding for members of the cytochrome P450 family were upregulated. The cytochrome P450 proteins contain heme as a cofactor and are involved in oxidoreduction. Significant changes were also observed in the expression of several mobile elements in the absence of PARP-1, suggesting that PARP-1 may be involved in regulating the expression of mobile elements.

The Nuclear Receptor Seven Up Regulates Genes Involved in Immunity and Xenobiotic Response in the Adult Drosophila Female Fat Body

The physiology of organisms depends on inter-organ communication in response to changes in the environment. Nuclear receptors are broadly expressed transcription factors that respond to circulating molecules to control many biological processes, including immunity, detoxification, and reproduction. Although the tissue-intrinsic roles of nuclear receptors in reproduction have been extensively studied, there is increasing evidence that nuclear receptor signaling in peripheral tissues can also influence oogenesis. We previously showed that the Drosophila nuclear receptor Seven up (Svp) is required in the adult fat body to regulate distinct steps of oogenesis; however, the relevant downstream targets of Svp remain unknown. Here, we took an RNA sequencing approach to identify candidate Svp targets specifically in the adult female fat body that might mediate this response. svp knockdown in the adult female fat body significantly downregulated immune genes involved in the first line of pathogen defense, suggesting a role for Svp in stimulating early immunity. In addition, we found that Svp transcriptionally regulates genes involved in each step of the xenobiotic detoxification response. Based on these findings, we propose a testable model in which Svp functions in the adult female fat body to stimulate early defense against pathogens and facilitate detoxification as part of its mechanisms to promote oogenesis.

Association between overexpression of cytochrome P450 genes and deltamethrin resistance in Rhipicephalus microplus

Cytochrome P450 monooxygenases mediated metabolic detoxification has been recognized as one of the mechanisms involved in resistance to pyrethroids, which is a class of pesticides that includes acaricides such as deltamethrin. Several cytochrome P450 (CYP) genes were identified in arthropod pests which are upregulated in response to exposure to pesticides used as acaricides. However, to date, limited information is available with respect to CYP genes and their response to acaricide exposure in ticks. We cloned and sequenced four CYP genes, the CYP41, CYP3006G8, CYP319A1 and CYP4W1 from reference susceptible IVRI-I strain of Rhipicephalus microplus. The expression pattern of the genes was investigated using qPCR in reference susceptible IVRI-I, pyrethroid-resistant IVRI-IV and multi-acaricide resistant IVRI-V strains. The effect of a single exposure of deltamethrin, at a concentration of 2600 μg/mL and 299.7 μg/mL on IVRI-IV and IVRI-V strains, respectively, on the expression of the four CYP genes was evaluated. In IVRI-IV strain, the CYP41 gene was highly overexpressed (FC 8.72) while CYP3006G8 was underexpressed with FC of 0.06. All the four genes were overexpressed in IVRI-V strain. After exposure to deltamethrin, the CYP3006G8 transcript levels were significantly upregulated at all time intervals in both resistant strains with the highest FC of 11.62 at 12 h in IVRI-IV and 13.38 at 3 h in IVRI-V. Our results suggest that the constitutive overexpression of CYP41 and deltamethrin induced upregulation of CYP3006G8 contribute to the development of pyrethroid resistance, specifically deltamethrin, in these two reference strains.

In Vivo Imaging with Genetically Encoded Redox Biosensors

Redox reactions are of high fundamental and practical interest since they are involved in both normal physiology and the pathogenesis of various diseases. However, this area of research has always been a relatively problematic field in the context of analytical approaches, mostly because of the unstable nature of the compounds that are measured. Genetically encoded sensors allow for the registration of highly reactive molecules in real-time mode and, therefore, they began a new era in redox biology. Their strongest points manifest most brightly in in vivo experiments and pave the way for the non-invasive investigation of biochemical pathways that proceed in organisms from different systematic groups. In the first part of the review, we briefly describe the redox sensors that were used in vivo as well as summarize the model systems to which they were applied. Next, we thoroughly discuss the biological results obtained in these studies in regard to animals, plants, as well as unicellular eukaryotes and prokaryotes. We hope that this work reflects the amazing power of this technology and can serve as a useful guide for biologists and chemists who work in the field of redox processes.

Low doses of the neonicotinoid insecticide imidacloprid induce ROS triggering neurological and metabolic impairments in Drosophila

Declining insect population sizes are provoking grave concern around the world as insects play essential roles in food production and ecosystems. Environmental contamination by intense insecticide usage is consistently proposed as a significant contributor, among other threats. Many studies have demonstrated impacts of low doses of insecticides on insect behavior, but have not elucidated links to insecticidal activity at the molecular and cellular levels. Here, the histological, physiological, and behavioral impacts of imidacloprid are investigated in Drosophila melanogaster, an experimental organism exposed to insecticides in the field. We show that oxidative stress is a key factor in the mode of action of this insecticide at low doses. Imidacloprid produces an enduring flux of Ca2+ into neurons and a rapid increase in levels of reactive oxygen species (ROS) in the larval brain. It affects mitochondrial function, energy levels, the lipid environment, and transcriptomic profiles. Use of RNAi to induce ROS production in the brain recapitulates insecticide-induced phenotypes in the metabolic tissues, indicating that a signal from neurons is responsible. Chronic low level exposures in adults lead to mitochondrial dysfunction, severe damage to glial cells, and impaired vision. The potent antioxidant, N-acetylcysteine amide (NACA), reduces the severity of a number of the imidacloprid-induced phenotypes, indicating a causal role for oxidative stress. Given that other insecticides are known to generate oxidative stress, this research has wider implications. The systemic impairment of several key biological functions, including vision, reported here would reduce the resilience of insects facing other environmental challenges.

Genomic and transcriptomic analyses in Drosophila suggest that the ecdysteroid kinase-like (EcKL) gene family encodes the 'detoxification-by-phosphorylation' enzymes of insects

Phosphorylation is a phase II detoxification reaction that, among animals, occurs near exclusively in insects, but the enzymes responsible have never been cloned or otherwise identified. We propose the hypothesis that members of the arthropod-specific ecdysteroid kinase-like (EcKL) gene family encode detoxicative kinases. To test this hypothesis, we annotated the EcKL gene family in 12 species of Drosophila and explored their evolution within the genus. Many ancestral EcKL clades are evolutionarily unstable and have experienced repeated gene gain and loss events, while others are conserved as single-copy orthologs. Leveraging multiple published gene expression datasets from D. melanogaster, and using the cytochrome P450s-a classical detoxification family-as a test case, we demonstrate relationships between xenobiotic induction, detoxification tissue-enriched expression and evolutionary instability in the EcKLs and the P450s. We devised a systematic method for identifying candidate detoxification genes in large gene families that is concordant with experimentally determined functions of P450 genes in D. melanogaster. Applying this method to the EcKLs suggested a significant proportion of these genes play roles in detoxification, and that the EcKLs may constitute a detoxification gene family in insects. Additionally, we estimate that between 11 and 16 uncharacterised D. melanogaster P450s are strong detoxification candidates. Lastly, we also found previously unreported genomic and transcriptomic variation in a number of EcKLs and P450s associated with toxic stress phenotypes using a targeted phenome-wide association study (PheWAS) approach in D. melanogaster, presenting multiple future avenues of research for detoxification genetics in this species.

Cyclophosphamide in Drosophila promotes genes and transposable elements differential expression and mitochondrial dysfunction

Cyclophosphamide (CPA) is an alkylating agent used for cancer chemotherapy, organ transplantation, and autoimmune disease treatment. Here, mRNA sequencing and high-resolution respirometry were performed to evaluate the alterations of Drosophila melanogaster gene expression fed with CPA under acute (0.1 mg/mL, for 24 h) and chronic (0.05 mg/mL, for 35 days) treatments. Differential expression analysis was performed using Cufflinks-Cuffdiff, DESeq2, and edgeR software. CPA affected genes are involved in several biological functions, including stress response and immune-related pathways, oxi-reduction and apoptotic processes, and cuticle and vitelline membrane formation. In particular, this is the first report of CPA-induced mitochondrial dysfunction caused by the downregulation of genes involved with mitochondria constituents. CPA treatment also changed the transcription pattern of transposable elements (TEs) from the gypsy and copia superfamilies. The results presented here provided evidence of CPA mitochondrial toxicity mechanisms and that CPA can modify TEs transcription in Drosophila flies.

Transcriptome analysis of antennal cytochrome P450s and their transcriptional responses to plant and locust volatiles in Locusta migratoria

Cytochrome P450 monooxygenases (P450s) constitute a large superfamily of heme-thiolate proteins that are involved in the biosynthesis or degradation of endogenous compounds and detoxification of exogenous chemicals. It has been reported that P450s could serve as odorant-degrading enzymes (ODEs) to inactivate odorants to avoid saturating the antennae. However, there is little information about P450s in the antennae of Locusta migratoria. In the current work, we conducted an antenna transcriptome analysis and identified 92 P450s, including 68 full-length and 24 partial sequences. Phylogenetic analysis showed that 68 full-length P450s were grouped into four clans: CYP2, CYP3, CYP4, and mitochondria clans. Tissue, stage, and sex-dependent expressions of these 68 P450s were investigated. The results showed that 4 P450s were antenna-specific, whereas others were antenna-rich but also expressed in other tissues, implying their various potential roles in the antennae. In addition, the responses of seven selected P450s to five gramineous plant volatiles and four locust volatiles were determined. CYP6MU1 could be induced by almost all compounds tested, suggesting its important roles in odorant processing. Different P450s exhibited diverse responses to odorants, indicating that specific regulation of P450 expression by odorants might modulate the sensitivity of the olfactory responses to various chemicals.

Candidate detoxification-related genes in brown planthopper, Nilaparvata lugens, in response to β-asarone based on transcriptomic analysis

Nilaparvata lugens(Stål) is a serious pest of rice and has evolved different levels of resistance against most chemical pesticides. β-asarone is the main bioactive insecticidal compound of Acorus calamus L. that shows strong insecticidal activity against pests. In this study, we conducted a bioassay experiment to determine the contact toxicity of β-asarone to N. lugens nymphs. The LD₃₀ sublethal dose was 0.106 μg per nymph, with 95% confidence limits of 0.070-0.140 μg. We applied the LD₃₀ concentration of β-asarone to nymphs for 24 h or 72 h and then performed a transcriptome sequence analysis by referencing the N. lugens genome to characterize the variation. The transcriptomic analysis showed that several GO terms and KEGG pathways presented significant changes. Individually, 126 differentially expressed genes (DEGs), including 72 upregulated and 54 downregulated genes, were identified at 24 h, and 1771 DEGs, including 882 upregulated and 889 downregulated genes, were identified at 72 h. From the DEGs, we identified a total of 40 detoxification-related genes, including eighteen Cytochrome P450 monooxygenase genes (P450s), three Glutathione S-transferase genes, one Carboxylesterase gene, twelve UDP-glucosyltransferases and six ATP-binding cassette genes. We selected the eighteen P450s for subsequent verification by quantitative PCR. These findings indicated that β-asarone presented strong contact toxicity to N. lugens nymphs and induced obvious variation of detoxification-related genes that may be involved in the response to β-asarone.

Copper exposure enhances Spodoptera litura larval tolerance to β-cypermethrin

Environmental xenobiotics can influence the tolerance of insects to chemical insecticides. Heavy metals are widespread distributed, can be easily bio-accumulated in plants and subsequently within phytophagous insects via the food chains. However, less attention has been paid to the effect of heavy metal exposure on their insecticide tolerance. In this study, pre-exposure of copper (Cu, 25-100 mg kg^-1) significantly enhanced the subsequent tolerance of Spodoptera litura to β-cypermethrin, a widely used pyrethroid insecticide in crop field. Cytochrome P450 monooxygenases (CYPs) activities were cross-induced in larvae exposed to Cu and β-cypermethrin, while the activities of glutathione S-transferase (GST) and carboxylesterase (CarE) were not affected. Application of piperonyl butoxide (PBO), a P450 synergist, effectively impaired the tolerance to β-cypermethrin in Cu-exposed S. litura larvae with a synergistic ratio of 1.72, indicating that P450s contribute to larval tolerance to β-cypermethrin induced by Cu exposure. Among the four CYP6AB family genes examined, only larval midgut-specific CYP6AB12 was found to be cross-induced by Cu and β-cypermethrin. RNA interference (RNAi)-mediated silencing of CYP6AB12 effectively decreased the mRNA levels of the target gene, and significantly reduced the larval tolerance to β-cypermethrin following exposure to Cu. These results showed that pre-exposure of heavy metal Cu enhanced larval tolerance to β-cypermethrin in S. litura, possibly through the cross-induction of P450s. Our findings provide new insights on the relationship between heavy metals and chemical insecticides that may benefit both the risk evaluation of heavy metal contamination and development of pest management strategies.

Expanding the canon: Non-classical mosquito genes at the interface of arboviral infection

Mosquito transmitted viruses cause significant morbidity and mortality in human populations. Despite the use of insecticides and other measures of vector control, arboviral diseases are on the rise. One potential solution for limiting disease transmission to humans is to render mosquitoes refractory to viral infection through genetic modification. Substantial research effort in Drosophila, Aedes and Anopheles has helped to define the major innate immune pathways, including Toll, IMD, Jak/Stat and RNAi, however we still have an incomplete picture of the mosquito antiviral response. Transcriptional profiles of virus-infected insects reveal a much wider range of pathways activated by the process of infection. Within these lists of genes are unexplored mosquito candidates of viral defense. Wolbachia species are endosymbiotic bacteria that naturally limit arboviral infection in mosquitoes. Our understanding of the Wolbachia-mediated viral blocking mechanism is poor, but it does not appear to operate via the classical immune pathways. Herein, we reviewed the transcriptomic response of mosquitoes to multiple viral species and put forth consensus gene types/families outside the immune canon whose expression responds to infection, including cytoskeleton and cellular trafficking, the heat shock response, cytochromes P450, cell proliferation, chitin and small RNAs. We then examine emerging evidence for their functional role in viral resistance in diverse insect and mammalian hosts and their potential role in Wolbachia-mediated viral blocking. These candidate gene families offer novel avenues for research into the nature of insect viral defense.

A high-fat diet impacts memory and gene expression of the head in mated female Drosophila melanogaster

Obesity predisposes humans to a range of life-threatening comorbidities, including type 2 diabetes and cardiovascular disease. Obesity also aggravates neural pathologies, such as Alzheimer's disease, but this class of comorbidity is less understood. When Drosophila melanogaster (flies) are exposed to high-fat diet (HFD) by supplementing a standard medium with coconut oil, they adopt an obese phenotype of decreased lifespan, increased triglyceride storage, and hindered climbing ability. The latter development has been previously regarded as a potential indicator of neurological decline in fly models of neurodegenerative disease. Our objective was to establish the obesity phenotype in Drosophila and identify a potential correlation, if any, between obesity and neurological decline through behavioral assays and gene expression microarray. We found that mated female w1118 flies exposed to HFD maintained an obese phenotype throughout adult life starting at 7 days, evidenced by increased triglyceride stores, diminished life span, and impeded climbing ability. While climbing ability worsened cumulatively between 7 and 14 days of exposure to HFD, there was no corresponding alteration in triglyceride content. Microarray analysis of the mated female w1118 fly head revealed HFD-induced changes in expression of genes with functions in memory, metabolism, olfaction, mitosis, cell signaling, and motor function. Meanwhile, an Aversive Phototaxis Suppression assay in mated female flies indicated reduced ability to recall an entrained memory 6 h after training. Overall, our results support the suitability of mated female flies for examining connections between diet-induced obesity and nervous or neurobehavioral pathology, and provide many directions for further investigation.

Identification of a novel cytochrome P450 CYP3356A1 linked with insecticide detoxification in Bradysia odoriphaga

BACKGROUND

Cytochrome P450 monooxygenases play an important role in the metabolic detoxification of insecticides in insect pests. However, little is known about the role of a specific P450 gene and its responses to insecticide exposure in Bradysia odoriphaga, a major pest in Chinese chive production.

RESULTS

In this study, a novel P450 gene, CYP3356A1, was cloned from Bradysia odoriphaga. The full-length cDNA sequence of CYP3356A1 is 2153 bp and its open reading frame (ORF) encodes 508 amino acids. Quantitative real time PCR(qRT-PCR) analyses in different tissues showed that CYP3356A1 expression was the highest in the Malpighian tubule. Moreover, among the different developmental stages of the insect, the highest expression of CYP3356A1 was found in fourth-instar larvae. Expression of CYP3356A1 was upregulated by treatment with imidacloprid, thiamethoxam, and β-cypermethrin at median lethal concentrations (LC₅₀ ). RNA interference (RNAi)-mediated silencing of CYP3356A1 significantly increased mortality by 36.90%, 25.17%, and 36.73 when fourth-instar B. odoriphaga larvae were exposed to imidacloprid, thiamethoxam, and β-cypermethrin, respectively, at the LC₅₀ dose.

CONCLUSION

These results demonstrate that CYP3356A1 is related to the detoxification of imidacloprid, thiamethoxam, and β-cypermethrin in B. odoriphaga. Moreover, the study also increased our understanding of the molecular mechanisms of insecticide detoxification in this pest insect. © 2018 Society of Chemical Industry.

High fat diet induces sex-specific differential gene expression in Drosophila melanogaster

Currently about 2 billion adults globally are estimated to be overweight and ~13% of them are obese. High fat diet (HFD) is one of the major contributing factor to obesity, heart disease, diabetes and cancer. Recent findings on the role of HFD in inducing abnormalities in neurocognition and susceptibility to Alzheimer’s disease are highly intriguing. Since fundamental molecular pathways are often conserved across species, studies involving Drosophila melanogaster as a model organism can provide insight into the molecular mechanisms involving human disease. In order to study some of such mechanisms in the central nervous system as well in the rest of the body, we investigated the effect of HFD on the transcriptome in the heads and bodies of male and female flies kept on either HFD or regular diet (RD). Using comprehensive genomic analyses which include high-throughput transcriptome sequencing, pathway enrichment and gene network analyses, we found that HFD induces a number of responses that are sexually dimorphic in nature. There was a robust transcriptional response consisting of a downregulation of stress-related genes in the heads and glycoside hydrolase activity genes in the bodies of males. In the females, the HFD led to an increased transcriptional change in lipid metabolism. A strong correlation also existed between the takeout gene and hyperphagic behavior in both males and females. We conclude that a) HFD induces a differential transcriptional response between males and females, in heads and bodies and b) the non-dimorphic transcriptional response that we identified was associated with hyperphagia. Therefore, our data on the transcriptional responses in flies to HFD provides potentially relevant information to human conditions including obesity.

Vgsc-interacting proteins are genetically associated with pyrethroid resistance in Aedes aegypti

Association mapping of factors that condition pyrethroid resistance in Aedes aegypti has consistently identified genes in multiple functional groups. Toward better understanding of the mechanisms involved, we examined high throughput sequencing data (HTS) from two Aedes aegypti aegypti collections from Merida, Yucatan, Mexico treated with either permethrin or deltamethrin. Exome capture enrichment for coding regions and the AaegL5 annotation were used to identify genes statistically associated with resistance. The frequencies of single nucleotide polymorphisms (SNPs) were compared between resistant and susceptible mosquito pools using a contingency χ² analysis. The -log₁₀(χ²p value) was calculated at each SNP site, with a weighted average determined from all sites in each gene. Genes with -log₁₀(χ²p value) ≥ 4.0 and present among all 3 treatment groups were subjected to gene set enrichment analysis (GSEA). We found that several functional groups were enriched compared to all coding genes. These categories were transport, signal transduction and metabolism, in order from highest to lowest statistical significance. Strikingly, 21 genes with demonstrated association to synaptic function were identified. In the high association group (n = 1,053 genes), several genes were identified that also genetically or physically interact with the voltage-gated sodium channel (VGSC). These genes were eg., CHARLATAN (CHL), a transcriptional regulator, several ankyrin-domain proteins, PUMILIO (PUM), a translational repressor, and NEDD4 (E3 ubiquitin-protein ligase). There were 13 genes that ranked among the top 10%: these included VGSC; CINGULIN, a predicted neuronal gap junction protein, and the aedine ortholog of NERVY (NVY), a transcriptional regulator. Silencing of CHL and NVY followed by standard permethrin bottle bioassays validated their association with permethrin resistance. Importantly, VGSC levels were also reduced about 50% in chl- or nvy-dsRNA treated mosquitoes. These results are consistent with the contribution of a variety of neuronal pathways to pyrethroid resistance in Ae. aegypti.

Drosophila as a Model for Developmental Toxicology: Using and Extending the Drosophotoxicology Model

Fruit flies, Drosophila melanogaster, have been traditionally valued as a simple model system due to their easy and inexpensive culture, their relatively compact genome, and the variety of available genetic tools. However, due to similarities of their neurological and developmental pathways with those of vertebrates, Drosophila also offers advantages for developmental toxicity assays. The ability to distinguish the effects of a toxicant on adult females, males, and the developing offspring adds to the usefulness of this model. Here we describe key techniques to screen chemicals and other potential emerging toxicants such as nanoparticles on adult Drosophila female and male reproductive success. In addition, assessments of relative toxicity can be revealed by viability assays at each developmental stage from the embryo to the pharate, or preemergent, adult.

Protein-protein interaction network analysis of insecticide resistance molecular mechanism in Drosophila melanogaster

The problem of resistance has not been solved fundamentally at present, because the development speed of new insecticides can not keep pace with the development speed of resistance, and the lack of understanding of molecular mechanism of resistance. Here we collected seed genes and their interacting proteins involved in insecticide resistance molecular mechanism in Drosophila melanogaster by literature mining and the String database. We identified a total of 528 proteins and 13514 protein-protein interactions. The protein interaction network was constructed by String and Pajek, and we analyzed the topological properties, such as degree centrality and eigenvector centrality. Proteasome complexes and drug metabolism-cytochrome P450 were an enrichment by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. This is the first time to explore the insecticide resistance molecular mechanism of D. melanogaster by the methods and tools of network biology, it can provide the bioinformatic foundation for further understanding the mechanisms of insecticide resistance.

Transcriptomic meta-signatures identified in Anopheles gambiae populations reveal previously undetected insecticide resistance mechanisms

Increasing insecticide resistance in malaria-transmitting vectors represents a public health threat, but underlying mechanisms are poorly understood. Here, a data integration approach is used to analyse transcriptomic data from comparisons of insecticide resistant and susceptible Anopheles populations from disparate geographical regions across the African continent. An unbiased, integrated analysis of this data confirms previously described resistance candidates but also identifies multiple novel genes involving alternative resistance mechanisms, including sequestration, and transcription factors regulating multiple downstream effector genes, which are validated by gene silencing. The integrated datasets can be interrogated with a bespoke Shiny R script, deployed as an interactive web-based application, that maps the expression of resistance candidates and identifies co-regulated transcripts that may give clues to the function of novel resistance-associated genes.

Increasing insecticide resistance of mosquitoes represents a public health threat, and underlying mechanisms are poorly understood. Here, Ingham et al. identify putative insecticide resistance genes in Anopheles gambiae populations across Africa and develop a web-based application that maps their expression.

Structural Variants and Selective Sweep Foci Contribute to Insecticide Resistance in the Drosophila Genetic Reference Panel

Patterns of nucleotide polymorphism within populations of Drosophila melanogaster suggest that insecticides have been the selective agents driving the strongest recent bouts of positive selection. However, there is a need to explicitly link selective sweeps to the particular insecticide phenotypes that could plausibly account for the drastic selective responses that are observed in these non-target insects. Here, we screen the Drosophila Genetic Reference Panel with two common insecticides; malathion (an organophosphate) and permethrin (a pyrethroid). Genome-wide association studies map survival on malathion to two of the largest sweeps in the D. melanogaster genome; Ace and Cyp6g1. Malathion survivorship also correlates with lines which have high levels of Cyp12d1, Jheh1 and Jheh2 transcript abundance. Permethrin phenotypes map to the largest cluster of P450 genes in the Drosophila genome, however in contrast to a selective sweep driven by insecticide use, the derived allele seems to be associated with susceptibility. These results underscore previous findings that highlight the importance of structural variation to insecticide phenotypes: Cyp6g1 exhibits copy number variation and transposable element insertions, Cyp12d1 is tandemly duplicated, the Jheh loci are associated with a Bari1 transposable element insertion, and a Cyp6a17 deletion is associated with susceptibility.

Comparative CYP-omic analysis between the DDT-susceptible and -resistant Drosophila melanogaster strains 91-C and 91-R

BACKGROUND

Cytochrome P450 monooxygenases (P450s) are involved in the biosynthesis of endogenous intracellular compounds and the metabolism of xenobiotics, including chemical insecticides. We investigated the structural and expression level variance across all P450 genes with respect to the evolution of insecticide resistance under multigenerational dichlorodiphenyltrichloroethane (DDT) selection.

RESULTS

RNA-sequencing (RNA-seq) and reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) indicated that the transcript levels of seven P450 genes were significantly up-regulated and three P450 genes were down-regulated in the DDT-resistant strain 91-R, as compared to the control strain 91-C. The overexpression of Cyp6g1 was associated with the presence of an Accord and an HMS-Beagle element insertion in the 5' upstream region in conjunction with copy number variation in the 91-R strain, but not in the 91-C strain. A total of 122 (50.2%) fixed nonsynonymous (amino acid-changing) mutations were found between 91-C and 91-R, and 20 (8.2%) resulted in amino acid changes within functional domains. Three P450 proteins were truncated as a result of premature stop codons and fixed between strains.

CONCLUSION

Our results demonstrate that a combination of changes in P450 protein-coding regions and transcript levels are possibly associated with DDT resistance, and thereby suggest that selection for variant function may occur within this gene family in response to chronic DDT exposure. © 2018 Society of Chemical Industry.

RNA-seq analysis of gene expression changes during pupariation in Bactrocera dorsalis (Hendel) (Diptera: Tephritidae)

Background

The oriental fruit fly, Bactrocera dorsalis (Hendel) has been considered to be one of the most important agricultural pest around the world. As a holometabolous insect, larvae must go through a metamorphosis process with dramatic morphological and structural changes to complete their development. To better understand the molecular mechanisms of these changes, RNA-seq of B. dorsalis from wandering stage (WS), late wandering stage (LWS) and white puparium stage (WPS) were performed.

Results

In total, 11,721 transcripts were obtained, out of which 1914 genes (578 up-regulated and 1336 down-regulated) and 2047 genes (655 up-regulated and 1392 down-regulated) were found to be differentially expressed between WS and LWS, as well as between WS and WPS, respectively. Of these DEGs, 1862 and 1996 genes were successfully annotated in various databases. The analysis of RNA-seq data together with qRT-PCR validation indicated that during this transition, the genes in the oxidative phosphorylation pathway, and genes encoding P450s, serine protease inhibitor, and cuticular proteins were down-regulated, while the serine protease genes were up-regulated. Moreover, we found some 20-hydroxyecdysone (20E) biosynthesis and signaling pathway genes had a higher expression in the WS, while the genes responsible for juvenile hormone (JH) synthesis, degradation, signaling and transporter pathways were down-regulated, suggesting these genes might be involved in the process of larval pupariation in B. dorsalis. For the chitinolytic enzymes, the genes encoding chitinases (chitinase 2, chitinase 5, chitinase 8, and chitinase 10) and chitin deacetylase might play the crucial role in the degradation of insect chitin with their expressions significantly increased during the transition. Here, we also found that chitin synthase 1A might be involved in the chitin synthesis of cuticles during the metamorphosis in B. dorsalis.

Conclusions

Significant changes at transcriptional level were identified during the larval pupariation of B. dorsalis. Importantly, we also obtained a vast quantity of RNA-seq data and identified metamorphosis associated genes, which would all help us to better understand the molecular mechanism of metamorphosis process in B. dorsalis.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5077-z) contains supplementary material, which is available to authorized users.

Changes in Neuronal Signaling and Cell Stress Response Pathways are Associated with a Multigenic Response of Drosophila melanogaster to DDT Selection

The adaptation of insect populations to insecticidal control is a continual threat to human health and sustainable agricultural practices, but many complex genomic mechanisms involved in this adaption remain poorly understood. This study applied a systems approach to investigate the interconnections between structural and functional variance in response to dichlorodiphenyltrichloroethane (DDT) within the Drosophila melanogaster strain 91-R. Directional selection in 6 selective sweeps coincided with constitutive gene expression differences in DDT resistant flies, including the most highly upregulated transcript, Unc-115 b, which plays a central role in axon guidance, and the most highly downregulated transcript, the angiopoietin-like CG31832, which is involved in directing vascular branching and dendrite outgrowth but likely may be under trans-regulatory control. Direct functions and protein–protein interactions mediated by differentially expressed transcripts control changes in cell migration, signal transduction, and gene regulatory cascades that impact the nervous system. Although changes to cellular stress response pathways involve 8 different cytochrome P450s, stress response, and apoptosis is controlled by a multifacetted regulatory mechanism. These data demonstrate that DDT selection in 91-R may have resulted in genome-wide adaptations that impacts genetic and signal transduction pathways that converge to modify stress response, cell survival, and neurological functions. This study implicates the involvement of a multigenic mechanism in the adaptation to a chemical insecticide, which impact interconnected regulatory cascades. We propose that DDT selection within 91-R might act systemically, wherein pathway interactions function to reinforce the epistatic effects of individual adaptive changes on an additive or nonadditive basis.

Genetic screening of the genes interacting with Drosophila FIG4 identified a novel link between CMT-causing gene and long noncoding RNAs

Neuron-specific knockdown of the dFIG4 gene, a Drosophila homologue of human FIG4 and one of the causative genes for Charcot-Marie-Tooth disease (CMT), reduces the locomotive abilities of adult flies, as well as causing defects at neuromuscular junctions, such as reduced synaptic branch length in presynaptic terminals of the motor neurons in third instar larvae. Eye imaginal disc-specific knockdown of dFIG4 induces abnormal morphology of the adult compound eye, the rough eye phenotype. In this study, we carried out modifier screening of the dFIG4 knockdown-induced rough eye phenotype using a set of chromosomal deficiency lines on the second chromosome. By genetic screening, we detected 9 and 15 chromosomal regions whose deletions either suppressed or enhanced the rough eye phenotype induced by the dFIG4 knockdown. By further genetic screening with mutants of individual genes in one of these chromosomal regions, we identified the gene CR18854 that suppressed the rough eye phenotype and the loss-of-cone cell phenotype. The CR18854 gene encodes a long non-coding RNA (lncRNA) consisting of 2566 bases. Mutation and knockdown of CR18854 patially suppressed the enlarged lysosome phenotype induced by Fat body-specific knockdown of dFIG4. Further characterization of CR18854, and a few other lncRNAs in relation to dFIG4 in neuron, using neuron-specific dFIG4 knockdown flies indicated a genetic link between the dFIG4 gene and lncRNAs including CR18854 and hsrω. We also obtained data indicating genetic interaction between CR18854 and Cabeza, a Drosophila homologue of human FUS, which is one of the causing genes for amyotrophic lateral sclerosis (ALS). These results suggest that lncRNAs such as CR18854 and hsrω are involved in a common pathway in CMT and ALS pathogenesis.

Mechanisms and Applications of Redox-Sensitive Green Fluorescent Protein-Based Hydrogen Peroxide Probes

SIGNIFICANCE

Genetically encoded hydrogen peroxide (H₂O₂) sensors, based on fusions between thiol peroxidases and redox-sensitive green fluorescent protein 2 (roGFP2), have dramatically broadened the available "toolbox" for monitoring cellular H₂O₂ changes. Recent Advances: Recently developed peroxiredoxin-based probes such as roGFP2-Tsa2ΔC_R offer considerably improved H₂O₂ sensitivity compared with previously available genetically encoded sensors and now permit dynamic, real-time, monitoring of changes in endogenous H₂O₂ levels.

CRITICAL ISSUES

The correct understanding and interpretation of probe read-outs is crucial for their meaningful use. We discuss probe mechanisms, potential pitfalls, and best practices for application and interpretation of probe responses and highlight where gaps in our knowledge remain.

FUTURE DIRECTIONS

The full potential of the newly available sensors remains far from being fully realized and exploited. We discuss how the ability to monitor basal H₂O₂ levels in real time now allows us to re-visit long-held ideas in redox biology such as the response to ischemia-reperfusion and hypoxia-induced reactive oxygen species production. Further, recently proposed circadian cycles of peroxiredoxin hyperoxidation might now be rigorously tested. Beyond their application as H₂O₂ probes, roGFP2-based H₂O₂ sensors hold exciting potential for studying thiol peroxidase mechanisms, inactivation properties, and the impact of post-translational modifications, in vivo. Antioxid. Redox Signal. 29, 552-568.

Behavior of detoxifying enzymes of Aedes aegypti exposed to girgensohnine alkaloid analog and Cymbopogon flexuosus essential oil

Because mosquito control depend on the use of commercial insecticides and resistance has been described in some of them, there is a need to explore new molecules no resistant. In vivo effects of girgensohnine analog 2-(3,4-dimethoxyphenyl)-2-(piperidin-1-yl)acetonitrile DPPA and Cymbopogon flexuosus essential oil CFEO, on the detoxifying enzymes acetylcholinesterase (AChE), glutathione-S-transferase (GST), nonspecific esterases (α- and β-), mixed function oxidases (MFO) and p-NPA esterases were evaluated on a Rockefeller (Rock) and wild Aedes aegypti population from Santander, Colombia (WSant). The action was tested after 24h of exposure at concentrations of 20.10, 35.18 and 70.35mgL^-1 of DPPA and 18.45, 30.75 and 61.50mgL^-1 of CFEO, respectively. It was found that AChE activity of Rock and WSant was not influenced by the evaluated concentration of DPPA and CFEO (p>0.05), while MFO activity was significantly affected by all CFEO concentrations in WSant (p<0.05). GST, α- and β-esterase activities were affected in Rock exposed at the highest CFEO concentration, this concentration also modified β-esterases activity of WSant. DPPA and CFEO sublethal doses induced inhibition of AChE activity on untreated larvae homogenate from 12 to 20% and 18 to 26%, respectively. For untreated adult homogenate, the inhibition activity raised up to 14 to 27% for DPPA and 26 to 34% for CFEO. Elevated levels of detoxifying enzymes, found when CFEO was evaluated, showed a larval sensitivity not observed by the pure compound suggesting that DPPA, contrary to CFEO, was not recognized, transformed or eliminated by the evaluated detoxifying enzymes.

Functional analysis of CYP6ER1, a P450 gene associated with imidacloprid resistance in Nilaparvata lugens

The cytochrome P450 CYP6ER1 has been reported to play an important role in imidacloprid resistance of the brown planthopper (BPH), Nilaparvata lugens, and is overexpressed in most resistant populations. In the present study, we confirmed that CYP6ER1 expression can be induced by certain levels of imidacloprid. Developmental expression analysis revealed that CYP6ER1 was expressed highly in the adult stage, and tissue distribution analysis showed that CYP6ER1 was expressed mainly in the fat body and midgut. RNA interference (RNAi) of CYP6ER1 and transgenic expression of CYP6ER1 in Drosophila melanogaster both suggested that the expression of CYP6ER1 is sufficient to confer imidacloprid resistance. Furthermore, we analyzed the interaction of imidacloprid and CYP6ER1 monooxygenase by using dynamic simulations and molecular docking. We found that Nitrogen atoms in the heterocycle of the imidacloprid molecule may bind to iron atoms in the center of the homology model of CYP6ER1 via 4,5-dihedro-1H-imidazole. This finding contributes to a better understanding of how CYP6ER1 takes part in the insecticide metabolism.

Metabolomic profiling of permethrin-treated Drosophila melanogaster identifies a role for tryptophan catabolism in insecticide survival

Insecticides and associated synergists are rapidly losing efficacy in target insect pest populations making the discovery of alternatives a priority. To discover novel targets for permethrin synergists, metabolomics was performed on permethrin-treated Drosophila melanogaster. Changes were observed in several metabolic pathways including those for amino acids, glycogen, glycolysis, energy, nitrogen, NAD(+), purine, pyrimidine, lipids and carnitine. Markers for acidosis, ammonia stress, oxidative stress and detoxification responses were also observed. Many of these changes had not been previously characterized after permethrin exposure. From the altered pathways, tryptophan catabolism was selected for further investigation. The knockdown of some tryptophan catabolism genes (vermilion, cinnabar and CG6950) in the whole fly and in specific tissues including fat body, midgut and Malpighian tubules using targeted RNAi resulted in altered survival phenotypes against acute topical permethrin exposure. The knockdown of vermilion, cinnabar and CG6950 in the whole fly also altered survival phenotypes against chronic oral permethrin, fenvalerate, DDT, chlorpyriphos and hydramethylnon exposure. Thus tryptophan catabolism has a previously uncharacterized role in defence against insecticides, and shows that metabolomics is a powerful tool for target identification in pesticide research.