RESUMO
Mounting evidence suggests that insect hormones associated with growth and development also participate in pathogen defense. We have discovered a previously undescribed midgut transcriptional control pathway that modulates the availability of 20-hydroxyecdysone (20E) in a worldwide insect pest (Plutella xylostella), allowing it to defeat the major virulence factor of an insect pathogen Bacillus thuringiensis (Bt). A reduction of the transcriptional inhibitor (PxDfd) increases the expression of a midgut microRNA (miR-8545), which in turn represses the expression of a newly identified ecdysteroid-degrading glucose dehydrogenase (PxGLD). Downregulation of PxGLD reduces 20E degradation to increase 20E titer and concurrently triggers a transcriptional negative feedback loop to mitigate 20E overproduction. The moderately elevated 20E titer in the midgut activates a MAPK signaling pathway to increase Bt tolerance/resistance. These findings deepen our understanding of the functions attributed to these classical insect hormones and help inform potential future strategies that can be employed to control insect pests.
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The bean flower thrip Megalurothrips usitatus (Bagnall) is a severe pest on cowpeas and causes a 20-30% reduction in cowpeas in Hainan, China, with even complete crop failure in severe cases. Spinetoram is currently the most important pesticide against M. usitatus in cowpea production. In the main producing areas of cowpeas in Hainan, however, the efficacy of spinetoram against M. usitatus is not well known. In the present study, we employed the maximum dose bioassay to evaluate the efficacy of the mortality rates of adult thrips at F0 in spinetoram, freshly collected from 212 field populations of M. usitatus collected from 20 villages in the Yazhou District of Hainan. Our results showed that the mortality rates of these thrip populations exposed to spinetoram were from 3.31% to 100%. Among them, the mortality rates of 66.98% (142/212) of the populations exceeded 80%, while that of 33.96% (72/212) of the populations surpassed 90%. Only a small proportion of 0.47% (1/212) the populations exhibited a mortality rate below 10%, and 4.72% (10/212) displayed rates below 50%. Furthermore, significant differences were also observed in the mortality rates of thrips among different villages. Taken together, the maximum dosage bioassay method is a rapid and easily implemented approach providing valuable insights into the field efficacy of insecticides and offers guidance in determining the optimal dosage required in the field. Spinetoram is still effective against M. usitatus in the main producing areas of cowpeas in Hainan, but caution should be exercised in its combined use with other methods to reduce potential resistance.
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Plant viral diseases compromise the growth and yield of the crop globally, and they tend to be more serious under extreme temperatures and drought climate changes. Currently, regulatory dynamics during plant development and in response to virus infection at the plant cell level remain largely unknown. In this study, single-cell RNA sequencing on 23 226 individual cells from healthy and tomato chlorosis virus-infected leaves was established. The specific expression and epigenetic landscape of each cell type during the viral infection stage were depicted. Notably, the mesophyll cells showed a rapid function transition in virus-infected leaves, which is consistent with the pathological changes such as thinner leaves and decreased chloroplast lamella in virus-infected samples. Interestingly, the F-box protein SKIP2 was identified to play a pivotal role in chlorophyll maintenance during virus infection in tomato plants. Knockout of the SlSKIP2 showed a greener leaf state before and after virus infection. Moreover, we further demonstrated that SlSKIP2 was located in the cytomembrane and nucleus and directly regulated by ERF4. In conclusion, with detailed insights into the plant responses to viral infections at the cellular level, our study provides a genetic framework and gene reference in plant-virus interaction and breeding in the future research.
Assuntos
Folhas de Planta , Solanum lycopersicum , Transcriptoma , Solanum lycopersicum/virologia , Solanum lycopersicum/genética , Solanum lycopersicum/crescimento & desenvolvimento , Folhas de Planta/virologia , Folhas de Planta/genética , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Análise de Célula Única , Doenças das Plantas/virologia , Doenças das Plantas/genética , Regulação da Expressão Gênica de Plantas , Crinivirus/genética , Crinivirus/fisiologiaRESUMO
Nitrogen is an essential element for all life on earth. Nitrogen metabolism, including excretion, is essential for growth, development, and survival of plants and animals alike. Several nitrogen metabolic processes have been described, but the underlying molecular mechanisms are unclear. Here, we reveal a unique process of nitrogen metabolism in the whitefly Bemisia tabaci, a global pest. We show that it has acquired two bacterial uricolytic enzyme genes, B. tabaci urea carboxylase (BtUCA) and B. tabaci allophanate hydrolase (BtAtzF), through horizontal gene transfer. These genes operate in conjunction to not only coordinate an efficient way of metabolizing nitrogenous waste but also control B. tabaci's exceptionally flexible nitrogen recycling capacity. Its efficient nitrogen processing explains how this important pest can feed on a vast spectrum of plants. This finding provides insight into how the hijacking of microbial genes has allowed whiteflies to develop a highly economic and stable nitrogen metabolism network and offers clues for pest management strategies.
Assuntos
Hemípteros , Animais , Hemípteros/genética , Hemípteros/metabolismo , Hemípteros/microbiologia , Genes Bacterianos , Plantas/genética , Nitrogênio/metabolismoRESUMO
Bioinsecticides and transgenic crops based on the bacterial pathogen Bacillus thuringiensis (Bt) can effectively control diverse agricultural insect pests, nevertheless, the evolution of resistance without obvious fitness costs has seriously eroded the sustainable use of these Bt products. Recently, it has been discovered that an increased titer of juvenile hormone (JH) favors an insect host (Plutella xylostella) to enhance fitness whilst resisting the Bt pathogen, however, the underlying regulatory mechanisms of the increased JH titer are obscure. Here, the involvement of N6 -methyladenosine (m6 A) RNA modification in modulating the availability of JH in this process is defined. Specifically, it is found that two m6 A methyltransferase subunit genes, PxMettl3 and PxMettl14, repress the expression of a key JH-degrading enzyme JH esterase (JHE) to induce an increased JH titer, mitigating the fitness costs associated with a robust defense against the Bt pathogen. This study identifies an as-yet uncharacterized m6 A-mediated epigenetic regulator of insect hormones for maintaining fitness during pathogen defense and unveils an emerging Bt resistance-related m6 A methylation atlas in insects, which further expands the functional landscape of m6 A modification and showcases the pivotal role of epigenetic regulation in host-pathogen interactions.
Assuntos
Bacillus thuringiensis , Mariposas , Animais , Mariposas/genética , Mariposas/metabolismo , RNA/metabolismo , Epigênese Genética/genética , Endotoxinas/genética , Endotoxinas/metabolismo , Endotoxinas/farmacologia , Toxinas de Bacillus thuringiensis/metabolismo , Insetos , Bacillus thuringiensis/genética , Bacillus thuringiensis/metabolismo , Hormônios Juvenis/metabolismo , MetilaçãoRESUMO
Polyunsaturated fatty acids (PUFAs) are essential nutrients for all living organisms. PUFA synthesis is mediated by Δ12 desaturases in plants and microorganisms, whereas animals usually obtain PUFAs through their diet. The whitefly Bemisia tabaci is an extremely polyphagous agricultural pest that feeds on phloem sap of many plants that do not always provide them with sufficient PUFAs. Here, a plant-derived Δ12 desaturase gene family BtFAD2 is characterized in B. tabaci and it shows that the BtFAD2-9 gene enables the pest to synthesize PUFAs, thereby significantly enhancing its fecundity. The role of BtFAD2-9 in reproduction is further confirmed by transferring the gene to Drosophila melanogaster, which also increases the fruit fly's reproduction. These findings reveal an extraordinary evolutionary scenario whereby a phytophagous insect acquired a family of plant genes that enables it to synthesize essential nutrients, thereby lessening its nutritional dependency and allowing it to feed and reproduce on many host plants.
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Ácidos Graxos Dessaturases , Hemípteros , Animais , Ácidos Graxos Dessaturases/genética , Hemípteros/genética , Drosophila melanogaster , Ácidos Graxos Insaturados , Estearoil-CoA Dessaturase , ReproduçãoRESUMO
The rapid evolution of pest resistance threatens the sustainable utilization of bioinsecticides such as abamectin, and so deciphering the molecular mechanisms affecting toxicity and resistance is essential for their long-term application. Historical studies of abamectin resistance in arthropods have mainly focused on mechanisms involving the glutamate-gated chloride channel (GluCl) targets, with the role of metabolic processes less clear. The two-spotted spider mite, Tetranychus urticae, is a generalist herbivore notorious for rapidly developing resistance to pesticides worldwide, and abamectin has been widely used for its control in the field. After reanalyzing previous transcriptome and RNA-seq data, we here identified an ABC transporter subfamily C gene in T. urticae named multidrug resistance-associated protein 1 (TuMRP1), whose expression differed between susceptible and resistant populations. Synergism bioassays with the inhibitor MK-571, the existence of a genetic association between TuMRP1 expression and susceptibility to abamectin, and the effect of RNA interference mediated silencing of TuMRP1 were all consistent with a direct role of this transporter protein in the toxicity of abamectin. Although ABC transporters are often involved in removing insecticidal compounds from cells, our data suggest either an alternative role for these proteins in the mechanism of action of abamectin or highlight an indirect association between their expression and abamectin toxicity.
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Tetranychidae , Animais , Tetranychidae/genética , Proteínas Associadas à Resistência a Múltiplos Medicamentos , Ivermectina/toxicidadeRESUMO
Ongoing host-pathogen interactions can trigger a coevolutionary arms race, while genetic diversity within the host can facilitate its adaptation to pathogens. Here, we used the diamondback moth (Plutella xylostella) and its pathogen Bacillus thuringiensis (Bt) as a model for exploring an adaptive evolutionary mechanism. We found that insect host adaptation to the primary Bt virulence factors was tightly associated with a short interspersed nuclear element (SINE - named SE2) insertion into the promoter of the transcriptionally activated MAP4K4 gene. This retrotransposon insertion coopts and potentiates the effect of the transcription factor forkhead box O (FOXO) in inducing a hormone-modulated Mitogen-activated protein kinase (MAPK) signaling cascade, leading to an enhancement of a host defense mechanism against the pathogen. This work demonstrates that reconstructing a cis-trans interaction can escalate a host response mechanism into a more stringent resistance phenotype to resist pathogen infection, providing a new insight into the coevolutionary mechanism of host organisms and their microbial pathogens.
Assuntos
Bacillus thuringiensis , Mariposas , Animais , Endotoxinas/farmacologia , Retroelementos/genética , Mariposas/metabolismo , Bacillus thuringiensis/metabolismo , Toxinas de Bacillus thuringiensis/metabolismo , Resistência a Inseticidas/genética , Larva/metabolismo , Proteínas de Bactérias/metabolismo , Proteínas Hemolisinas/metabolismoRESUMO
Maintaining fitness during pathogen infection is vital for host survival as an excessive response can be as detrimental as the infection itself. Fitness costs are frequently associated with insect hosts countering the toxic effect of the entomopathogenic bacterium Bacillus thuringiensis (Bt), which delay the evolution of resistance to this pathogen. The insect pest Plutella xylostella has evolved a mechanism to resist Bt toxins without incurring significant fitness costs. Here, we reveal that non-phosphorylated and phosphorylated forms of a MAPK-modulated transcription factor fushi tarazu factor 1 (FTZ-F1) can respectively orchestrate down-regulation of Bt Cry1Ac toxin receptors and up-regulation of non-receptor paralogs via two distinct binding sites, thereby presenting Bt toxin resistance without growth penalty. Our findings reveal how host organisms can co-opt a master molecular switch to overcome pathogen invasion with low cost, and contribute to understanding the underlying mechanism of growth-defense tradeoffs during host-pathogen interactions in P. xylostella.
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Bacillus thuringiensis , Mariposas , Animais , Bacillus thuringiensis/metabolismo , Toxinas de Bacillus thuringiensis , Proteínas de Bactérias/metabolismo , Medicamentos de Ervas Chinesas , Endotoxinas/metabolismo , Proteínas Hemolisinas/metabolismo , Insetos/metabolismo , Resistência a Inseticidas/genética , Larva/metabolismo , Fatores de Transcrição/metabolismoRESUMO
Rapid evolution of resistance in crop pests to Bacillus thuringiensis (Bt) products threatens their widespread use, especially as pests appear to develop resistance through a range of different physiological adaptations. With such a diverse range of mechanisms reported, researchers have resorted to multi-omic approaches to understand the molecular basis of resistance. Such approaches generate a lot of data making it difficult to establish where causal links between physiological changes and resistance exist. In this study, a combination of RNA-Seq and iTRAQ was used with a strain of diamondback moth, Plutella xylostella (L.), whose resistance mechanism is well understood. While some of the causal molecular changes in the resistant strain were detected, other previously verified changes were not detected. We suggest that while multi-omic studies have use in validating a proposed resistance mechanism, they are of limited value in identifying such a mechanism in the first place.
Assuntos
Bacillus thuringiensis , Mariposas , Animais , Bacillus thuringiensis/genética , Toxinas de Bacillus thuringiensis , Proteínas de Bactérias/genética , Proteínas de Bactérias/farmacologia , Endotoxinas/genética , Proteínas Hemolisinas/genética , Proteínas Hemolisinas/farmacologia , Resistência a Inseticidas/genética , Larva/genética , Mariposas/genéticaRESUMO
Deciphering the molecular mechanisms of insect resistance to Bacillus thuringiensis (Bt) based biotechnology products including Bt sprays and Bt crops is critical for the long-term application of Bt technology. Previously, we established that down-regulation of the ABC transporter gene PxABCG1, trans-regulated by the MAPK signaling pathway, contributed to high-level resistance to Bt Cry1Ac toxin in diamondback moth, Plutella xylostella (L.). However, the underlying transcriptional regulatory mechanism was unknown. Herein, we identified putative binding sites (PBSs) of the transcription factor (TF) POUM1 in the PxABCG1 promoter and used a dual-luciferase reporter assay (DLRA) and yeast one-hybrid (Y1H) assay to reveal that POUM1 activates PxABCG1 via interaction with one of these sites. The expression of POUM1 was significantly decreased in the midgut tissue of Cry1Ac-resistant P. xylostella strains compared to a Cry1Ac-susceptible P. xylostella strain. Silencing of POUM1 expression resulted in reduced expression of the PxABCG1 gene and an increase in larval tolerance to Bt Cry1Ac toxin in the Cry1Ac-susceptible P. xylostella strain. Furthermore, silencing of PxMAP4K4 expression increased the expression of both POUM1 and PxABCG1 genes in the Cry1Ac-resistant P. xylostella strain. These results indicate that the POUM1 induces PxABCG1 expression, while the activated MAPK cascade represses PxABCG1 expression thus reducing Cry1Ac susceptibility in P. xylostella. This result deepens our understanding of the transcriptional regulatory mechanism of midgut Cry receptor genes and the molecular basis of the evolution of Bt resistance in insects.
Assuntos
Bacillus thuringiensis , Mariposas , Animais , Bacillus thuringiensis/genética , Bacillus thuringiensis/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Proteínas de Bactérias/farmacologia , Endotoxinas/metabolismo , Endotoxinas/farmacologia , Proteínas Hemolisinas/metabolismo , Proteínas Hemolisinas/farmacologia , Proteínas de Insetos/genética , Resistência a Inseticidas/genética , Larva/genética , Larva/metabolismo , Mariposas/genética , Mariposas/metabolismo , Fatores de Transcrição/genéticaRESUMO
The benefits of biopesticides and transgenic crops based on the insecticidal Cry-toxins from Bacillus thuringiensis (Bt) are considerably threatened by insect resistance evolution, thus, deciphering the molecular mechanisms underlying insect resistance to Bt products is of great significance to their sustainable utilization. Previously, we have demonstrated that the down-regulation of PxmALP in a strain of Plutella xylostella (L.) highly resistant to the Bt Cry1Ac toxin was due to a hormone-activated MAPK signaling pathway and contributed to the resistance phenotype. However, the underlying transcriptional regulatory mechanism remains enigmatic. Here, we report that the PxGATAd transcription factor (TF) is responsible for the differential expression of PxmALP observed between the Cry1Ac susceptible and resistant strains. We identified that PxGATAd directly activates PxmALP expression via interacting with a non-canonical but specific GATA-like cis-response element (CRE) located in the PxmALP promoter region. A six-nucleotide insertion mutation in this cis-acting element of the PxmALP promoter from the resistant strain resulted in repression of transcriptional activity, affecting the regulatory performance of PxGATAd. Furthermore, silencing of PxGATAd in susceptible larvae reduced the expression of PxmALP and susceptibility to Cry1Ac toxin. Suppressing PxMAP4K4 expression in the resistant larvae transiently recovered both the expression of PxGATAd and PxmALP, indicating that the PxGATAd is a positive responsive factor involved in the activation of PxmALP promoter and negatively regulated by the MAPK signaling pathway. Overall, this study deciphers an intricate regulatory mechanism of PxmALP gene expression and highlights the concurrent involvement of both trans-regulatory factors and cis-acting elements in Cry1Ac resistance development in lepidopteran insects.
Assuntos
Toxinas de Bacillus thuringiensis/metabolismo , Endotoxinas/metabolismo , Proteínas Hemolisinas/metabolismo , Resistência a Inseticidas/genética , Sistema de Sinalização das MAP Quinases/fisiologia , Animais , Bacillus thuringiensis/genética , Bacillus thuringiensis/metabolismo , Toxinas de Bacillus thuringiensis/farmacologia , Proteínas de Bactérias/genética , Endotoxinas/farmacologia , Granulovirus/genética , Proteínas Hemolisinas/farmacologia , Proteínas de Insetos/genética , Inseticidas/metabolismo , Larva/genética , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Mariposas/genética , Mariposas/metabolismo , Fatores de Transcrição/genéticaRESUMO
BACKGROUND: Biopesticides and transgenic crops based on Bacillus thuringiensis (Bt) toxins are extensively used to control insect pests, but the rapid evolution of insect resistance seriously threatens their effectiveness. Bt resistance is often polygenic and complex. Mutations that confer resistance occur in midgut proteins that act as cell surface receptors for the toxin, and it is thought they facilitate its assembly as a membrane-damaging pore. However, the mechanistic details of the action of Bt toxins remain controversial. RESULTS: We have examined the contribution of two paralogous ABC transporters and two aminopeptidases N to Bt Cry1Ac toxicity in the diamondback moth, Plutella xylostella, using CRISPR/Cas9 to generate a series of homozygous polygenic knockout strains. A double-gene knockout strain, in which the two paralogous ABC transporters ABCC2 and ABCC3 were deleted, exhibited 4482-fold resistance to Cry1A toxin, significantly greater than that previously reported for single-gene knockouts and confirming the mutual functional redundancy of these ABC transporters in acting as toxin receptors in P. xylostella. A double-gene knockout strain in which APN1 and APN3a were deleted exhibited 1425-fold resistance to Cry1Ac toxin, providing the most direct evidence to date for these APN proteins acting as Cry1Ac toxin receptors, while also indicating their functional redundancy. Genetic crosses of the two double-gene knockouts yielded a hybrid strain in which all four receptor genes were deleted and this resulted in a > 34,000-fold resistance, indicating that while both types of receptor need to be present for the toxin to be fully effective, there is a level of functional redundancy between them. The highly resistant quadruple knockout strain was less fit than wild-type moths, but no fitness cost was detected in the double knockout strains. CONCLUSION: Our results provide direct evidence that APN1 and APN3a are important for Cry1Ac toxicity. They support our overarching hypothesis of a versatile mode of action of Bt toxins, which can compensate for the absence of individual receptors, and are consistent with an interplay among diverse midgut receptors in the toxins' mechanism of action in a super pest.
Assuntos
Bacillus thuringiensis , Mariposas , Transportadores de Cassetes de Ligação de ATP/genética , Transportadores de Cassetes de Ligação de ATP/metabolismo , Animais , Bacillus thuringiensis/genética , Bacillus thuringiensis/metabolismo , Toxinas de Bacillus thuringiensis , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Proteínas de Bactérias/toxicidade , Antígenos CD13/genética , Antígenos CD13/metabolismo , Endotoxinas/genética , Endotoxinas/toxicidade , Proteínas Hemolisinas/genética , Proteínas Hemolisinas/toxicidade , Proteínas de Insetos/genética , Proteínas de Insetos/metabolismo , Resistência a Inseticidas/genética , Larva/genética , Mariposas/genéticaRESUMO
The two-spotted spider mite Tetranychus urticate is an important agricultural pest worldwide. It is extremely polyphagous and has developed resistance to many pesticides. Here, we assessed the pesticide resistance of seven field populations of T. urticae in China, their target site mutations and the activities of their detoxification enzymes. The results showed that abamectin and the traditional pesticides pyridaben, profenofos and bifenthrin had higher resistance or lower toxicity than more recently developed pesticides including chlorfenapyr, spinetoram, cyflumetofen, cyenopyrafen, bifenazate and B-azolemiteacrylic. The frequency of point mutations related to abamectin resistance, G314D in the glutamate-gated chloride channel 1 (GluCl1) and G326E in GluCl3, ranged 47%-70% and 0%-97%, respectively. The frequency of point mutations in A1215D and F1538I of the voltage-gated sodium channel gene (VGSC), which may increase resistance to pyrethroids, ranged 88%-100% and 10%-100%, respectively. For target sites related to organophosphate resistance, mutation frequencies ranged 25%-92% for G119S and 0%-23% for A201S in the acetycholinesterase gene (Ace). Mutation G126S in the bifenazate resistance-related cytochrome b gene (Cytb) was observed in three of the seven T. urticae populations. Higher activities of detoxification enzymes (P450, GST, CarEs and UGTs) were observed in two T. urticae populations, with significant difference in the XY-SX population. These results provide useful information on the status of pesticide resistance of T. urticae in China and suggest that T. urticae field populations may have multiple resistance mechanisms.
Assuntos
Acaricidas , Praguicidas , Tetranychidae , Canais de Sódio Disparados por Voltagem , Acaricidas/farmacologia , Agricultura , Animais , Mutação , Tetranychidae/genética , Canais de Sódio Disparados por Voltagem/genéticaRESUMO
BACKGROUND: Whitefly (Bemisia tabaci) is a typical pest that causes severe damage to hundreds of agricultural crops. The trehalose-6-phosphate synthase (TPS) genes, as the key genes in the insect trehalose synthesis pathway, are important for insect growth and development. The whitefly TPS genes may be a main reason for the severe damage and may represent potential targets for the control of whiteflies. RESULTS: In this study, we identified and cloned three TPS genes from B. tabaci MED and found that the BtTPS1 and BtTPS2 genes showed higher expression levels than the BtTPS3 gene. Then, RNA interference (RNAi) of BtTPS1 and BtTPS2 resulted in significant mortality and influenced the expression of related genes involved in energy metabolism and chitin biosynthesis in whitefly adults. Finally, the transgenic tobacco plants showed a significant effect on B. tabaci, and knockdown of BtTPS1 or BtTPS2 led to retarded growth and low hatchability in whitefly nymphs, and caused 90% mortality and decreased the fecundity in whitefly adults. Additionally, the transgenic tobacco with combinatorial RNAi of BtTPS1 and BtTPS2 showed a better efficacy against whiteflies than individual silencing. CONCLUSION: Our results suggest that silencing of the BtTPS genes can compromise the growth and development of whiteflies, offering not only a new option for whitefly control but also a secure and environmentally friendly management strategy.
Assuntos
Hemípteros , Animais , Produtos Agrícolas , Hemípteros/genética , Plantas Geneticamente Modificadas/genética , Interferência de RNA , Nicotiana/genéticaRESUMO
Host-pathogen interactions are central components of ecological networks where the MAPK signaling pathways act as central hubs of these complex interactions. We have previously shown that an insect hormone modulated MAPK signaling cascade participates as a general switch to trans-regulate differential expression of diverse midgut genes in the diamondback moth, Plutella xylostella (L.) to cope with the insecticidal action of Cry1Ac toxin, produced by the entomopathogenic bacterium Bacillus thuringiensis (Bt). The relationship between topology and functions of this four-tiered phosphorylation signaling cascade, however, is an uncharted territory. Here, we carried out a genome-wide characterization of all the MAPK orthologs in P. xylostella to define their phylogenetic relationships and to confirm their evolutionary conserved modules. Results from quantitative phosphoproteomic analyses, combined with functional validations studies using specific inhibitors and dsRNAs lead us to establish a MAPK "road map", where p38 and ERK MAPK signaling pathways, in large part, mount a resistance response against Bt toxins through regulating the differential expression of multiple Cry toxin receptors and their non-receptor paralogs in P. xylostella midgut. These data not only advance our understanding of host-pathogen interactions in agricultural pests, but also inform the future development of biopesticides that could suppress Cry resistance phenotypes.
Assuntos
Infecções por Bactérias Gram-Positivas/metabolismo , Interações Hospedeiro-Patógeno/fisiologia , Sistema de Sinalização das MAP Quinases/fisiologia , Mariposas/metabolismo , Mariposas/microbiologia , Animais , Bacillus thuringiensis , Toxinas de Bacillus thuringiensis/metabolismo , Endotoxinas/metabolismo , Infecções por Bactérias Gram-Positivas/veterinária , Proteínas Hemolisinas/metabolismo , Resistência a InseticidasRESUMO
In most organisms, various physiological and behavioral functions are expressed rhythmically. Previous studies have shown that thermoperiod is an important factor affecting circadian clock-related genes that regulate insect locomotor activity. Bradysia odoriphaga Yang & Zhang is an underground pest that attacks more than 30 crops but is especially damaging to Chinese chives. In this study, we analyzed the adult eclosion time and period (Boper) gene expression in B. odoriphaga as affected by temperature (cycling vs constant temperature), insect stage, and tissue specific. We found that the eclosion time and expression of the Boper gene changed during the temperature cycle but not under a constant temperature. Silencing of Boper expression significantly decreased the adult eclosion rate and significantly increased adult mortality and malformation. The findings indicate that thermoperiod alters Boper expression and regulates the eclosion rhythm.
Assuntos
Cebolinha-Francesa , Dípteros , Animais , Ritmo Circadiano/genética , Dípteros/genética , Expressão Gênica , Nematóceros , TemperaturaRESUMO
The molecular mechanisms of insect resistance to Cry toxins generated from the bacterium Bacillus thuringiensis (Bt) urgently need to be elucidated to enable the improvement and sustainability of Bt-based products. Although downregulation of the expression of midgut receptor genes is a pivotal mechanism of insect resistance to Bt Cry toxins, the underlying transcriptional regulation of these genes remains elusive. Herein, we unraveled the regulatory mechanism of the downregulation of the ABC transporter gene PxABCG1 (also called Pxwhite), a functional midgut receptor of the Bt Cry1Ac toxin in Plutella xylostella. The PxABCG1 promoters of Cry1Ac-susceptible and Cry1Ac-resistant strains were cloned and analyzed, and they showed clear differences in activity. Subsequently, a dual-luciferase reporter assay, a yeast one-hybrid (Y1H) assay, and RNA interference (RNAi) experiments demonstrated that a cis-mutation in a binding site of the Hox transcription factor Antennapedia (Antp) decreased the promoter activity of the resistant strain and eliminated the binding and regulation of Antp, thereby enhancing the resistance of P. xylostella to the Cry1Ac toxin. These results advance our knowledge of the roles of cis- and trans-regulatory variations in the regulation of midgut Cry receptor genes and the evolution of Bt resistance, contributing to a more complete understanding of the Bt resistance mechanism.
Assuntos
Membro 1 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/genética , Toxinas de Bacillus thuringiensis/genética , Proteínas de Insetos/genética , Resistência a Inseticidas/genética , Receptores de Superfície Celular/genética , Animais , Bacillus thuringiensis/genética , Endotoxinas/genética , Lepidópteros/efeitos dos fármacos , Lepidópteros/genética , Mutação/genética , Regiões Promotoras Genéticas/genéticaRESUMO
N 6-methyladenosine (m6A) is the most prevalent messenger RNA modification in eukaryotes and an important posttranscriptional regulator of gene expression. However, the biological roles of m6A in most insects remain largely unknown. Here, we show that m6A regulates a cytochrome P450 gene (CYP4C64) in the global whitefly pest, Bemisia tabaci, leading to insecticide resistance. Investigation of the regulation of CYP4C64, which confers resistance to the insecticide thiamethoxam, revealed a mutation in the 5' untranslated region of this gene in resistant B. tabaci strains that introduces a predicted m6A site. We provide several lines of evidence that mRNA methylation of the adenine at this position, in combination with modified expression of m6A writers, acts to increase expression of CYP4C64 and resistance. Collectively, these results provide an example of the epitranscriptomic regulation of the xenobiotic response in insects and implicate the m6A regulatory axis in the development of insecticide resistance.