Whitefly hijacks a plant detoxification gene that neutralizes plant toxins.

Plants protect themselves with a vast array of toxic secondary metabolites, yet most plants serve as food for insects. The evolutionary processes that allow herbivorous insects to resist plant defenses remain largely unknown. The whitefly Bemisia tabaci is a cosmopolitan, highly polyphagous agricultural pest that vectors several serious plant pathogenic viruses and is an excellent model to probe the molecular mechanisms involved in overcoming plant defenses. Here, we show that, through an exceptional horizontal gene transfer event, the whitefly has acquired the plant-derived phenolic glucoside malonyltransferase gene BtPMaT1. This gene enables whiteflies to neutralize phenolic glucosides. This was confirmed by genetically transforming tomato plants to produce small interfering RNAs that silence BtPMaT1, thus impairing the whiteflies' detoxification ability. These findings reveal an evolutionary scenario whereby herbivores harness the genetic toolkit of their host plants to develop resistance to plant defenses and how this can be exploited for crop protection.

Retrotransposon-mediated evolutionary rewiring of a pathogen response orchestrates a resistance phenotype in an insect host.

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.

MAPK-mediated transcription factor GATAd contributes to Cry1Ac resistance in diamondback moth by reducing PxmALP expression.

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.

mTORC1-GLUT1-mediated glucose metabolism drives hyperactivation of B cells in primary Sjogren's syndrome.

Primary Sjögren's syndrome (pSS) is a chronic systemic autoimmune disease characterized by B cell hyperactivation and hypergrammaglobulinemia. Currently, the role of metabolic pathways in the B cells of pSS patients is poorly defined. Here, we showed that upon cytosine phosphate-guanine (CpG)/sCD40L/IL-4 stimulation, B cells proportionally increased glycolysis and oxygen consumption, and compared with B cells from healthy controls (HCs), B cells from pSS patients exhibited higher glycolysis capacity and maximal oxidative respiration (OXPHOS). We also found that glucose transporter 1 (GLUT1) expression in B cells from pSS patients was significantly higher than that in B cells from HCs. Treatment with 2-deoxy-d-glucose (2-DG) inhibited the activation of B cells in pSS patients. Both 2-DG and Metformin inhibited the proliferation, formation of plasma/plasmablasts and decreased the IgG and IgM levels in the supernatants of B cells from pSS patients. Furthermore, inhibition of mTORC1 by rapamycin had an effect similar to that of 2-DG, suppressing B cell activation, proliferation and antibody production. Taken together, we demonstrated that B cells from pSS patients are more metabolically active than those from HCs and suggested that the mTORC1-GLUT1 glycolysis pathways were the major drivers of B cell hyperactivation and autoantibody production in pSS patients.

The regulation landscape of MAPK signaling cascade for thwarting Bacillus thuringiensis infection in an insect host.

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.

A novel salivary effector, BtE3, is essential for whitefly performance on host plants.

The whitefly Bemisia tabaci is a piercing-sucking herbivore that reduces the yields of crops both by feeding on plants and transmitting plant viruses. Like most plant feeders, B. tabaci has evolved ways to avoid plant defence responses. For example, B. tabaci is known to secrete salivary effectors to suppress host defences. However, the nature of B. tabaci effectors is not completely understood. In this study, we used B. tabaci genomic and salivary gland transcriptomic data and an overexpression system to identify a previously unknown B. tabaci salivary effector, BtE3. BtE3 is specifically expressed in the head (containing primary salivary glands) and is secreted into hosts during B. tabaci feeding. In planta overexpression of BtE3 blocked Burkholderia glumae-induced hypersensitive response (HR) in both Nicotiana benthamiana and Solanum lycopersicum. Silencing of BtE3 by plant-mediated RNAi prevented B. tabaci from continuously ingesting phloem sap, and reduced B. tabaci survival and fecundity. Moreover, overexpression of BtE3 in planta up-regulated the salicylic acid- (SA-) signalling pathway, but suppressed the downstream jasmonic acid- (JA-) mediated defences. Taken together, these results indicate that BtE3 is a B. tabaci-specific novel effector involved in B. tabaci-plant interactions. These findings increase our understanding of B. tabaci effectors and suggest novel strategies for B. tabaci pest management.

MAPK-directed activation of the whitefly transcription factor CREB leads to P450-mediated imidacloprid resistance.

The evolution of insect resistance to pesticides poses a continuing threat to agriculture and human health. While much is known about the proximate molecular and biochemical mechanisms that confer resistance, far less is known about the regulation of the specific genes/gene families involved, particularly by trans-acting factors such as signal-regulated transcription factors. Here we resolve in fine detail the trans-regulation of CYP6CM1, a cytochrome P450 that confers resistance to neonicotinoid insecticides in the whitefly Bemisia tabaci, by the mitogen-activated protein kinase (MAPK)-directed activation of the transcription factor cAMP-response element binding protein (CREB). Reporter gene assays were used to identify the putative promoter of CYP6CM1, but no consistent polymorphisms were observed in the promoter of a resistant strain of B. tabaci (imidacloprid-resistant, IMR), which overexpresses this gene, compared to a susceptible strain (imidacloprid-susceptible, IMS). Investigation of potential trans-acting factors using in vitro and in vivo assays demonstrated that the bZIP transcription factor CREB directly regulates CYP6CM1 expression by binding to a cAMP-response element (CRE)-like site in the promoter of this gene. CREB is overexpressed in the IMR strain, and inhibitor, luciferase, and RNA interference assays revealed that a signaling pathway of MAPKs mediates the activation of CREB, and thus the increased expression of CYP6CM1, by phosphorylation-mediated signal transduction. Collectively, these results provide mechanistic insights into the regulation of xenobiotic responses in insects and implicate both the MAPK-signaling pathway and a transcription factor in the development of pesticide resistance.

Seed priming with rutin enhances tomato resistance against the whitefly Bemisia tabaci.

Flavonoids are ubiquitously distributed in plants, showing pleiotropic effects in defense against abiotic and biotic stresses. Although it has been shown that seed priming with flavonoids can enhance plant resistance to abiotic stress, little is known about its potential to enhance plant tolerance to biotic stresses, especially for herbivorous insects. Here, we investigated whether treatment of tomato (Solanum lycopersicum) seeds with rutin improves plant resistance against the whitefly (Bemisia tabaci). Specifically, we measured the effect of rutin seed treatment on tomato seedling vigour, plant growth, feeding behavior and performance of B. tabaci on plants grown from control and rutin-treated seeds, and plant defense responses to B. tabaci attack. We found that seed treatment with different concentrations of rutin (viz 1, 2, 5, 10, and 20 mM) had minimal impact on shoot growth. Furthermore, seed treatment of rutin reduced the developmental rate of nymphs, the fecundity and feeding efficiency of adult females on plants grown from these seeds. The enhanced resistance of tomato against B. tabaci is closely associated with increased flavonoids accumulation, callose deposition and the expression of jasmonic acid (JA)-dependent defense genes. Additionally, callose deposition and expression of JA-dependent genes in tomato plants grown from rutin-treated seeds significantly increased upon B. tabaci infestation. These results suggest that seed treatment with rutin primes tomato resistance against B. tabaci, and are not accompanied by reductions in shoot growth. Defense priming by seed treatments may therefore be suitable for commercial exploitation.

Assessment of the role of an ABCC transporter TuMRP1 in the toxicity of abamectin to Tetranychus urticae.

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.

A versatile contribution of both aminopeptidases N and ABC transporters to Bt Cry1Ac toxicity in the diamondback moth.

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.

MAPK-Activated Transcription Factor PxJun Suppresses PxABCB1 Expression and Confers Resistance to Bacillus thuringiensis Cry1Ac Toxin in Plutella xylostella (L.).

Deciphering the molecular mechanisms underlying insect resistance to Cry toxins produced by Bacillus thuringiensis (Bt) is pivotal for the sustainable utilization of Bt biopesticides and transgenic Bt crops. Previously, we identified that mitogen-activated protein kinase (MAPK)-mediated reduced expression of the PxABCB1 gene is associated with Bt Cry1Ac resistance in the diamondback moth, Plutella xylostella (L.). However, the underlying transcriptional regulation mechanism remains enigmatic. Here, the PxABCB1 promoter in Cry1Ac-susceptible and Cry1Ac-resistant P. xylostella strains was cloned and analyzed and found to contain a putative Jun binding site (JBS). A dual-luciferase reporter assay and yeast one-hybrid assay demonstrated that the transcription factor PxJun repressed PxABCB1 expression by interacting with this JBS. The expression levels of PxJun were increased in the midguts of all resistant strains compared to the susceptible strain. Silencing of PxJun expression significantly elevated PxABCB1 expression and Cry1Ac susceptibility in the resistant NIL-R strain, and silencing of PxMAP4K4 expression decreased PxJun expression and also increased PxABCB1 expression. These results indicate that MAPK-activated PxJun suppresses PxABCB1 expression to confer Cry1Ac resistance in P. xylostella, deepening our understanding of the transcriptional regulation of midgut Cry receptor genes and the molecular basis of insect resistance to Bt Cry toxins. IMPORTANCE The transcriptional regulation mechanisms underlying reduced expression of Bt toxin receptor genes in Bt-resistant insects remain elusive. This study unveils that a transcription factor PxJun activated by the MAPK signaling pathway represses PxABCB1 expression and confers Cry1Ac resistance in P. xylostella. Our results provide new insights into the transcriptional regulation mechanisms of midgut Cry receptor genes and deepen our understanding of the molecular basis of insect resistance to Bt Cry toxins. To our knowledge, this study identified the first transcription factor that can be involved in the transcriptional regulation mechanisms of midgut Cry receptor genes in Bt-resistant insects.

Anlotinib enhances the antitumor activity of radiofrequency ablation on lung squamous cell carcinoma.

Anlotinib is a novel molecular targeted drug that has been approved for the treatment of lung adenocarcinoma. Currently these agents are rarely used in the treatment of lung squamous cell carcinoma (LSCC). Bronchoscope-guided radiofrequency ablation (RFA) is a new strategy proposed for the treatment of LSCC that is able to alleviate the obstruction of the respiratory tract caused by LSCC by direct destruction of the tumor tissues. The presence work aims to reveal whether Anlotinib could enhance the antitumor activity of RFA on LSCC cells. The results from real-time PCR (qPCR) confirmed overexpression of targets of anlotinib activity, including receptor tyrosine kinase or the MPAK/PI3K-AKT pathway kinases, in LSCC tissues. Treatment with anlotinib inhibited the survival, in vitro invasion, and migration of LSCC cells. Moreover, the antitumor effects of RFA were investigated using a rodent model of LSCC. The combination of RFA and anlotinib treatment enhanced the antitumor effect of RFA treatment. We propose a combinative strategy of RFA and anlotinib as a novel approach for successful management of LSCC.

Analysis of the antennal transcriptome and odorant-binding protein expression profiles of the parasitoid wasp Encarsia formosa.

The parasitoid of whiteflies Encarsia formosa has been widely applied to reduce whitefly-mediated damage on vegetables and ornamental plants grown in greenhouses. Although its chemosensory behavior has been described, the mechanism by which E. formosa recognizes chemical volatiles at the molecular level remains unknown. In this study, we obtained 66,632 unigenes from antennae transcriptomic architecture of E. formosa, of which 19,473 (29.2%) were functionally annotated. All that matters is that we manually identified 39 odorant-binding proteins (OBPs) from above dataset, and further investigated the tissue and stage-specific expression profiles of all identified OBP genes by real-time quantitative PCR. Among these OBP genes, 32 were enriched in antennae, and 2 in body. In addition, 4 OBPs were highly expressed in pupae, and 32 in 6-hour-age adults after eclosion. In addition to identifying OBP genes from E. formosa, this study provides a molecular basis for further functional studies of OBPs and the interactions of hosts and parasitic wasps.

Comparative transcriptome analysis of differentially expressed genes in Bradysia odoriphaga Yang et Zhang (Diptera: Sciaridae) at different acute stress temperatures.

The gnat, Bradysia odoriphaga Yang et Zhang, is an important underground pest in Asia. B. odoriphaga differ in heat and cold tolerance and exhibit quite different developmental strategies. To understand the underlying mechanisms, we sequenced and compared the transcriptome of B. odoriphaga under 40 °C (a stressful high temperature), 25 °C, and 4 °C (a stressful low temperature) for 1 h. We found that metabolism- and ribosome-related genes were modulated. In high temperature (40 °C), heat shock protein (HSP) genes, detoxication genes, metabolism genes, protein turnover genes, and stress signal transduction genes were differentially expressed. In low temperature (4 °C), genes related with heat shock protein (HSP) and detoxication were differentially expressed. Our study increases our understanding of the complex molecular mechanisms involved in the responses of B. odoriphaga to acute temperature stress and provides a potential strategy for pest management.

Alteration of CD226/TIGIT immune checkpoint on T cells in the pathogenesis of primary Sjögren's syndrome.

OBJECTIVES: Hyperactivity of T lymphocytes might play an important role in the pathogenesis of primary Sjögren's syndrome (pSS). CD226/T cell immunoglobulin and ITIM domain (TIGIT) pathway is a newly identified immune checkpoint involved in the pathogenesis of cancer and rheumatic diseases. However, its role in the pathophysiology of pSS is obscure. Hence, this study aimed to explore the potential role of CD226/TIGIT expression on T cells in the pathogenesis of pSS. METHODS: In patients with pSS, other rheumatic disease controls (DCs), and healthy controls (HCs), the expression of CD226 and TIGIT on T cells along with their activity following stimulation were detected by flow cytometry. The correlations between the expression of CD226 and TIGIT on T cells and clinical data were analyzed. RESULTS: The frequencies of CD226/TIGIT expressing CD4+ and CD8+ T cells were significantly higher in patients with pSS than in HCs and DCs. Among them, the TIGIT/CD226 expressing CD4+ T cells closely correlated with pSS disease activity: the percentages of CD4+CD226+ and CD4+TIGIT+ T cells were significantly higher in the active pSS than the inactive pSS. The proportion of CD4+TIGIT+ T cells positively correlated with the erythrocyte sedimentation rate. Further in vitro analysis revealed that CD4+CD226+ T cells exerted superior effector function than the CD226- counterparts in both pSS and HCs. TIGIT was preferably expressed on activated cells, and the activity of CD4+TIGIT+ T cells was comparable with CD4+TIGIT- T cells in HCs. However, in pSS, CD4+TIGIT+ T cells showed enhanced activity than the CD4+ TIGIT- T cells. CONCLUSION: CD226/TIGIT checkpoint molecules were over-expressed on T cells in pSS. Proportional and functional alteration of CD226/TIGIT expressing CD4+ T cells may be involved in the pathogenesis of pSS, and be a potential novel therapeutic target for the disease.

Antagonizing miR-7 suppresses B cell hyperresponsiveness and inhibits lupus development.

OBJECTIVES: The objective of this study was to address the biological function of miR-7 in an animal model of systemic lupus erythematosus. METHODS: MRLlpr/lpr lupus mice were administrated antagomiR-7 or a scramble control by tail vein for 5weeks. Three groups of animals' tissues were assessed for lupus manifestations by immunofluorescence and immunohistochemistry, and serum was examined for levels of autoantibodies and inflammatory cytokines. Splenic B cell subsets were assessed for intracellular expression of PI3K signaling by FACS. Finally, the ability of the miR-7 antagomir to regulate the expansion of T follicular helper (Tfh) cells and B cell hyperresponsiveness was further explored. RESULTS: We found that miR-7 was up-regulated in MRLlpr/lpr lupus mice and directly targeted PTEN mRNA in B cells. Up-regulated miR-7 in MRLlpr/lpr lupus B cells was negatively correlated with PTEN expression. Notably, miR-7 antagomir treatment reduced lupus manifestations in MRLlpr/lpr lupus mice. miR-7-mediated down-regulation of PTEN/AKT signaling promoted B cell differentiation into plasmablasts/plasma cells and spontaneous germinal center (GC) formation, whereas miR-7 antagomir normalized splenic B cell subtypes. Besides suppressing the activation of B cells, miR-7 antagomir intervention also down-regulated STAT3 phosphorylation and production of IL-21 and reduced Tfh expansion. CONCLUSION: The above data have demonstrated the critical roles of miR-7 not only in regulating PTEN expression and also B cell and Tfh cell function in lupus-prone MRLlpr/lpr lupus mice. Furthermore, the disease manifestations in MRLlpr/lpr lupus mice are efficiently improved by miR-7 antagomir, indicating miR-7 as a potential treatment strategy in SLE.

Metagenomic profiling of the pro-inflammatory gut microbiota in ankylosing spondylitis.

OBJECTIVE: Gut dysbiosis has been reported implicated in ankylosing spondylitis (AS), a common chronic inflammatory disease mainly affects sacroiliac joints and spine. Utilizing deep sequencing on the feces of untreated AS patients, our study aimed at providing an in-depth understanding of AS gut microbiota. METHODS: We analyzed the fecal metagenome of 85 untreated AS patients and 62 healthy controls by metagenomic shotgun sequencing, and 23 post-treatment feces of those AS patients were collected for comparison. Comparative analyses among different cohorts including AS, rheumatoid arthritis and Behcet's disease were performed to uncover some common signatures related to inflammatory arthritis. Molecular mimicry of a microbial peptide was also demonstrated by ELISpot assay. RESULTS: We identified AS-enriched species including Bacteroides coprophilus, Parabacteroides distasonis, Eubacterium siraeum, Acidaminococcus fermentans and Prevotella copri. Pathway analysis revealed increased oxidative phosphorylation, lipopolysaccharide biosynthesis and glycosaminoglycan degradation in AS gut microbiota. Microbial signatures of AS gut selected by random forest model showed high distinguishing accuracy. Some common signatures related to autoimmunity, such as Bacteroides fragilis and type III secretion system (T3SS), were also found. Finally, in vitro experiments demonstrated an increased amount of IFN-γ producing cells triggered by a bacterial peptide of AS-enriched species, mimicking type II collagen. CONCLUSIONS: These findings collectively indicate that gut microbiota was perturbed in untreated AS patients with diagnostic potential, and some AS-enriched species might be triggers of autoimmunity by molecular mimicry. Additionally, different inflammatory arthritis shared some common microbial signatures.

Defence priming in tomato by the green leaf volatile (Z)-3-hexenol reduces whitefly transmission of a plant virus.

Green leaf volatiles (GLVs) can induce defence priming, that is, can enable plants to respond faster or more strongly to future stress. The effects of priming by GLVs on defence against insect herbivores and pathogens have been investigated, but little is known about the potential of GLVs to prime crops against virus transmission by vector insects. Here, we tested the hypothesis that exposure to the GLV Z-3-hexenol (Z-3-HOL) can prime tomato (Solanum lycopersicum) for an enhanced defence against subsequent Tomato yellow leaf curl virus (TYLCV) transmission by the whitefly Bemisia tabaci. Bioassays showed that Z-3-HOL priming reduced subsequent plant susceptibility to TYLCV transmission by whiteflies. Z-3-HOL treatment increased transcripts of jasmonic acid (JA) biosynthetic genes and increased whitefly-induced transcripts of salicylic acid (SA) biosynthetic genes in plants. Using chemical inducers, transgenics and mutants, we demonstrated that induction of JA reduced whitefly settling and successful whitefly inoculation, while induction of SA reduced TYLCV transmission by whiteflies. Defence gene transcripts and flavonoid levels were enhanced when whiteflies fed on Z-3-HOL-treated plants. Moreover, Z-3-HOL treatment reduced the negative impact of whitefly infestation on tomato growth. These findings suggest that Z-3-HOL priming may be a valuable tool for improving management of insect-transmitted plant viruses.

Molecular characterization of an NADPH cytochrome P450 reductase from Bemisia tabaci Q: Potential involvement in susceptibility to imidacloprid.

NADPH cytochrome P450 reductase (CPR) is an integral component of cytochrome P450-mediated biological reactions, such as the metabolism of xenobiotics, including insecticides. CPR has been reported to be associated with insecticide tolerance in several insects. However, the biochemical characteristics and biological function of CPR in Bemisia tabaci Q (BtCPR) remain undefined. In this study, BtCPR was cloned, and bioinformatic analysis showed that BtCPR is a transmembrane protein with a molecular weight (MW) of 76.73 kDa and contains conserved binding domains (FMN, FAD, and NADPH). Tissue- and developmental stage-dependent expression indicated that the highest expression levels of BtCPR occurred in head tissue and in male adults. Transcripts of BtCPR in the field B. tabaci Q strain were 1.62-fold higher than those of the laboratory B. tabaci Q strain. In both field and laboratory adults, the susceptibility of BtCPR-knockdown B. tabaci Q to imidacloprid substantially increased compared to that of the B. tabaci Q control group. Furthermore, the heterologous expression of BtCPR in Sf9 cells exhibited catalytic activity for cytochrome c reduction, following Michaelis-Menten kinetics. Sf9 cells overexpressing BtCPR had greater viability than the control cells when treated with imidacloprid. The results suggest that BtCPR could affect the susceptibility of B. tabaci Q to imidacloprid and could also be considered a novel target for pest control.