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1.
PLoS One ; 16(10): e0258836, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34714845

RESUMO

Cultivated cotton, such as Gossypium hirsutum L., produces extrafloral (EF) nectar on leaves (foliar) and reproductive structures (bracteal) as an indirect anti-herbivore defense. In exchange for this carbohydrate-rich substance, predatory insects such as ants protect the plant against herbivorous insects. Some EF nectar-bearing plants respond to herbivory by increasing EF nectar production. For instance, herbivore-free G. hirsutum produces more bracteal than foliar EF nectar, but increases its foliar EF nectar production in response to herbivory. This study is the first to test for systemically induced changes to the carbohydrate composition of bracteal EF nectar in response to foliar herbivory on G. hirsutum. We found that foliar herbivory significantly increased the sucrose content of bracteal EF nectar while glucose and fructose remained unchanged. Sucrose content is known to influence ant foraging behavior and previous studies of an herbivore-induced increase to EF nectar caloric content found that it led to increased ant activity on the plant. As a follow-up to our finding, ant recruitment to mock EF nectar solutions that varied in sucrose content was tested in the field. The ants did not exhibit any preference for either solution, potentially because sucrose is a minor carbohydrate component in G. hirsutum EF nectar: total sugar content was not significantly affected by the increase in sucrose. Nonetheless, our findings raise new questions about cotton's inducible EF nectar responses to herbivory. Further research is needed to determine whether an herbivore-induced increase in sucrose content is typical of Gossypium spp., and whether it constitutes a corollary of systemic sucrose induction, or a potentially adaptive mechanism which enhances ant attraction to the plant.


Assuntos
Formigas/fisiologia , Gossypium/química , Sacarose/química , Animais , Gossypium/parasitologia , Herbivoria , Folhas de Planta/química , Folhas de Planta/parasitologia , Néctar de Plantas/química
2.
Sci Rep ; 11(1): 14172, 2021 07 08.
Artigo em Inglês | MEDLINE | ID: mdl-34238948

RESUMO

Cotton leaf curl disease (CLCuD), caused by begomoviruses in combination with betasatellite molecule, has adversely affected cotton industry of Indian subcontinent. To devise a CLCuD-control strategy, RNAi-mediated approach was followed in this study. Gossypium hirsutum cv. HS6 plants were transformed with intron-hairpin RNAi (ihpRNAi-C4) construct carrying silencing suppressor C4 gene of Cotton leaf curl Multan virus (CLCuMuV). Efficacy of the construct in imparting CLCuD resistance was evaluated in transgenic (T0, T1) cotton lines. Accumulation of CLCuMuV/betasatellite and attenuation of CLCuD symptoms in the transgenic lines were monitored at different times interval after virus inoculation. Northern hybridization revealed the expression of C4-gene derived siRNA. Expression of the ihpRNAi transcript was recorded higher in transgenic lines expressing siRNA which supposedly targeted the C4 gene. A significant delay in detection of virus as well as betasatellite was observed in the transgenic lines. At 30 days post inoculation (dpi), none of the lines tested positive. At 45 dpi, however, it could be detected in few lines having much lower titre as compared to non-transformed control plants. Notably, till 60 dpi, no significant progression of the virus/betasatellite DNA was observed and the plants did not exhibit any characteristic CLCuD symptoms. A tolerance phenomenon leading to escape of CLCuD symptoms in the transformed cotton was described.


Assuntos
Begomovirus/genética , Engenharia Genética , Gossypium/virologia , Íntrons/genética , Conformação de Ácido Nucleico , Animais , DNA Satélite/genética , Genoma de Planta , Gossypium/parasitologia , Hemípteros/fisiologia , Doenças das Plantas/virologia , Plantas Geneticamente Modificadas , Transformação Genética
3.
PLoS One ; 16(5): e0251134, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33945577

RESUMO

The efficacy and non-target arthropod effects of transgenic DAS-21023-5 × DAS-24236-5 × SYN-IR102-7 Bt cotton, expressing proteins Cry1Ac, Cry1F and Vip3Aa19, was examined through field trials in Brazil. Fifteen field efficacy experiments were conducted from 2014 through the 2020 growing season across six different states in Brazil to evaluate performance against key lepidopteran pests through artificial infestations of Chrysodeixis includens (Walker), Spodoptera frugiperda (J.E. Smith,1797), Spodoptera cosmioides (Walker, 1858) and Chloridea virescens (F., 1781), and natural infestations of Alabama argillacea (Hübner) and S. frugiperda. The impact of this Bt cotton technology on the non-target arthropod community in Brazilian cotton production systems was also assessed in a multi-site experiment. DAS-21023-5 × DAS-24236-5 × SYN-IR102-7 cotton significantly reduced the feeding damage caused by S. frugiperda, S. cosmioides, C. includens, C. virescens and A. argillacea, causing high levels of mortality (greater than 99%) to all target lepidopteran pests evaluated during vegetative and/or reproductive stages of crop development. Non-target arthropod community-level analyses confirmed no unintended effects on the arthropod groups monitored. These results demonstrate the value of transgenic Bt cotton containing event DAS-21023-5 × DAS-24236-5 × SYN-IR102-7 for consideration as part of an integrated approach for managing key lepidopteran pests in Brazilian cotton production systems.


Assuntos
Ácido 4-Acetamido-4'-isotiocianatostilbeno-2,2'-dissulfônico/análogos & derivados , Artrópodes/crescimento & desenvolvimento , Gossypium/metabolismo , Gossypium/parasitologia , Ácido 4-Acetamido-4'-isotiocianatostilbeno-2,2'-dissulfônico/metabolismo , Animais , Brasil , Controle de Insetos , Larva/crescimento & desenvolvimento , Mariposas/crescimento & desenvolvimento , Controle Biológico de Vetores/métodos , Folhas de Planta/parasitologia , Plantas Geneticamente Modificadas/parasitologia , Spodoptera/crescimento & desenvolvimento
4.
Sci Rep ; 11(1): 10377, 2021 05 17.
Artigo em Inglês | MEDLINE | ID: mdl-34001946

RESUMO

Crops genetically engineered to produce insecticidal proteins from Bacillus thuringiensis (Bt) have many benefits and are important globally for managing insect pests. However, the evolution of pest resistance to Bt crops reduces their benefits. Understanding the genetic basis of such resistance is needed to better monitor, manage, and counter pest resistance to Bt crops. Previous work shows that resistance to Bt toxin Cry2Ab is associated with mutations in the gene encoding the ATP-binding cassette protein ABCA2 in lab- and field-selected populations of the pink bollworm (Pectinophora gossypiella), one of the world's most destructive pests of cotton. Here we used CRISPR/Cas9 gene editing to test the hypothesis that mutations in the pink bollworm gene encoding ABCA2 (PgABCA2) can cause resistance to Cry2Ab. Consistent with this hypothesis, introduction of disruptive mutations in PgABCA2 in a susceptible strain of pink bollworm increased the frequency of resistance to Cry2Ab and facilitated creation of a Cry2Ab-resistant strain. All Cry2Ab-resistant individuals tested in this study had disruptive mutations in PgABCA2. Overall, we found 17 different disruptive mutations in PgABCA2 gDNA and 26 in PgABCA2 cDNA, including novel mutations corresponding precisely to single-guide (sgRNA) sites used for CRISPR/Cas9. Together with previous results, these findings provide the first case of practical resistance to Cry2Ab where evidence identifies a specific gene in which disruptive mutations can cause resistance and are associated with resistance in field-selected populations.


Assuntos
Transportadores de Cassetes de Ligação de ATP/genética , Toxinas de Bacillus thuringiensis/genética , Gossypium/parasitologia , Resistência a Inseticidas/genética , Inseticidas/farmacologia , Animais , Bacillus thuringiensis/genética , Sistemas CRISPR-Cas/genética , Humanos , Larva/efeitos dos fármacos , Larva/genética , Larva/patogenicidade , Lepidópteros/efeitos dos fármacos , Lepidópteros/genética , Lepidópteros/patogenicidade , Mariposas/genética , Mariposas/patogenicidade , Mutação/genética
5.
PLoS One ; 16(4): e0249699, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33831084

RESUMO

Plants have developed various mechanisms to respond specifically to each biotrophic attack. It has been shown that the electrical signals emitted by plants are associated with herbivory stress responses and can lead to the activation of multiple defences. Bt cotton is a genetically modified pest-resistant plant that produces an insecticide from Bacillus thuringiensis (Bt) to control Lepidopteran species. Surprisingly, there is no study-yet, that characterizes the signalling mechanisms in transgenic cotton plants attacked by non-target insects, such as aphids. In this study, we characterized the production of electrical signals on Bt and non-Bt cotton plants infested with Aphis gossypii and, in addition, we characterized the dispersal behaviour of aphids to correlate this behaviour to plant signalling responses. Electrical signalling of the plants was recorded with an extracellular measurement technique. Impressively, our results showed that both Bt and non-Bt cotton varieties, when attacked by A. gossypii, emitted potential variation-type electrical signals and clearly showed the presence of distinct responses regarding their perception and the behaviour of aphids, with evidence of delay, in terms of signal amount, and almost twice the amount of Cry1F protein was observed on Bt cotton plants at the highest density of insects/plant. We present in our article some hypotheses that are based on plant physiology and insect behaviour to explain the responses found on Bt cotton plants under aphid stress.


Assuntos
Afídeos/microbiologia , Bacillus thuringiensis/metabolismo , Gossypium/microbiologia , Gossypium/parasitologia , Estresse Fisiológico/fisiologia , Animais , Gossypium/genética , Herbivoria/fisiologia , Insetos/microbiologia , Inseticidas/metabolismo , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/microbiologia , Plantas Geneticamente Modificadas/parasitologia , Transdução de Sinais/genética , Estresse Fisiológico/genética
6.
Genes (Basel) ; 12(4)2021 03 29.
Artigo em Inglês | MEDLINE | ID: mdl-33805320

RESUMO

Alkaline phosphatases (ALPs: EC 3.1.3.1) are ubiquitous enzymes and play crucial roles in the fundamental phosphate uptake and secretory processes. Although insects are regarded as the most diverse group of organisms, the current understanding of ALP roles in insects is limited. As one type of destructive agricultural pest, whitefly Bemisia tabaci, a phloem feeder and invasive species, can cause extensive crop damage through feeding and transmitting plant diseases. In this study, we retrieved five ALP genes in MEAM1 whitefly, nine ALP genes in MED whitefly via comparative genomics approaches. Compared with nine other insects, whiteflies' ALP gene family members did not undergo significant expansion during insect evolution, and whiteflies' ALP genes were dispersed. Moreover, whiteflies' ALP gene family was conserved among insects and emerged before speciation via phylogenetic analysis. Whiteflies' ALP gene expression profiles presented that most ALP genes have different expression patterns after feeding on cotton or tobacco plants. Female/male MED whiteflies possessed higher ALP activities on both cotton and tobacco plants irrespective of sex, relative to MEAM1 whiteflies. Meanwhile, adult MED whiteflies possessed higher ALP activity in both whole insect and salivary samples, relative to MEAM1 whiteflies. We also found that both MED and MEAM1 whiteflies could upregulate ALP activities after feeding on cotton compared with feeding on tobacco plants. These findings demonstrated the functions of whiteflies ALPs and will assist the further study of the genomic evolution of insect ALPs.


Assuntos
Fosfatase Alcalina/metabolismo , Gossypium/parasitologia , Hemípteros/fisiologia , Proteínas de Insetos/metabolismo , Doenças das Plantas/parasitologia , Tabaco/parasitologia , Fosfatase Alcalina/genética , Animais , Feminino , Perfilação da Expressão Gênica , Hemípteros/enzimologia , Proteínas de Insetos/genética , Masculino
7.
Int J Biol Macromol ; 180: 539-546, 2021 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-33722622

RESUMO

To combat insect pests and vectors that are responsible for high losses in food and lives, insecticide discovery is of top priority. This study aimed to synthesize, characterize and investigate the insecticidal activity of 1,3,4-oxadiazole derivatives grafted on chitosan (CS) and modified polymethyl methacrylate (PMMA). 5-(pyridin-3-yl)-1,3,4-oxadiazole-2-thiol and 5-(pyridin-4-yl)-1,3,4-oxadiazole-2-thiol were respectively reacted with ethylchloroacetate and methyl-2-choloroacetoacetate. The resulted esters were grafted with CS and modified-PMMA. The products were characterized using FT-IR, 1H NMR, TGA, and XRD techniques. Four CS grafted ones were able to show good insecticidal activity against the cotton leafworm Spodoptera littoralis. Furthermore, the safety of these compounds was tested using MTT assay on a human cell line (WI-38). The results indicated that compounds 2a, 2b, 6a, and 6d are considered insecticide candidates to S. littoralis fourth-instar larvae. Cytotoxicity of 2b and 6d indicated that they are the least toxic to humans. It is concluded that both compounds may represent promising insecticide candidates.


Assuntos
Quitosana/química , Inseticidas/química , Oxidiazóis/química , Polimetil Metacrilato/química , Spodoptera/crescimento & desenvolvimento , Animais , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Gossypium/parasitologia , Humanos , Inseticidas/síntese química , Inseticidas/farmacologia , Larva/efeitos dos fármacos , Larva/crescimento & desenvolvimento , Modelos Químicos , Estrutura Molecular , Espectroscopia de Infravermelho com Transformada de Fourier , Difração de Raios X
8.
Sci Rep ; 11(1): 2101, 2021 01 22.
Artigo em Inglês | MEDLINE | ID: mdl-33483556

RESUMO

The toxicity of seven biorational insecticides [five insect growth regulators (Buprofezin, Fenoxycarb, Pyriproxyfen, Methoxyfenozide, and Tebufenozide) and two oil-extracts of neem and bitter gourd seeds] against Bemisia tabaci and their selectivity for its parasitoid, Encarsia formosa were evaluated in laboratory and field conditions for 2 years (2018-2019) in Pakistan. Toxicity results demonstrate that Pyriproxyfen, Buprofezin, and Fenoxycarb proved to be effective (80-91% mortality and 66.3-84.2% population-reduction) against B. tabaci followed by Methoxyfenozide, Tebufenozide (50-75% mortality and 47.8-52.4% population-reduction), and then oil-extracts of neem and bitter gourd (25-50% mortality and 36.5-39.8% population-reduction) in the laboratory [72 h post-application exposure interval (PAEI)] and field trails (168 h PAEI), respectively. All tested biorationals, except Methoxyfenozide [(slightly-harmful/Class-II), i.e., causing mortality of parasitoids between a range of 25-50%] and Tebufenozide [(moderately-harmful/Class-III), i.e., causing mortality of parasitoids between the ranges of 51-75%], proved harmless/Class-I biorationals at PAEI of 7-days in the field (parasitism-reduction < 25%) and 3-days in the lab (effect < 30%). In laboratory bioassays, exposure of parasitized-pseudopupae and adult-parasitoids to neem and bitter gourd oils demonstrated that these compounds proved harmless/Class-I biorationals (< 30% mortality). Alternatively, Pyriproxyfen, Buprofezin, Fenoxycarb, Methoxyfenozide, and Tebufenozide were slightly-harmful biorationals (30-79% mortality) against the respective stages of E. formosa. We conclude that most of the tested biorationals proved harmless or slightly harmful to E. formosa, except tebufenozide after PAEI of 7-days (168 h) in the field and, therefore, may be used strategically in Integrated Pest Management (IPM) of B. tabaci.


Assuntos
Gossypium/parasitologia , Hemípteros/fisiologia , Inseticidas/toxicidade , Controle Biológico de Vetores/métodos , Vespas/fisiologia , Animais , Azadirachta/química , Gossypium/genética , Interações Hospedeiro-Parasita/efeitos dos fármacos , Hidrazinas/toxicidade , Hormônios Juvenis/toxicidade , Larva/efeitos dos fármacos , Larva/fisiologia , Momordica charantia/química , Fenilcarbamatos/toxicidade , Extratos Vegetais/toxicidade , Plantas Geneticamente Modificadas , Piridinas/toxicidade , Tiadiazinas/toxicidade , Resultado do Tratamento
9.
Sci Rep ; 11(1): 436, 2021 01 11.
Artigo em Inglês | MEDLINE | ID: mdl-33432040

RESUMO

There is a global concern about the effects of climate change driven shifts in species phenology on crop pests. Using geographically and temporally extensive data set of moth trap catches and temperatures across the cotton growing states of India, we predicted the phenology of cotton pink bollworm Pectinophora gossypiella (Saunders). Our approach was centered on growing degree days (GDD), a measure of thermal accumulation that provides a mechanistic link between climate change and species' phenology. The phenology change was predicted by calculating absolute error associated with DD and ordinal date, an alternative predictor of phenology, for peak moth abundance. Our results show that GDD outperformed the ordinal dates in predicting peak moth abundance in 6 out of 10 selected locations. Using established thresholds of 13.0/34.0 °C, mean DD accumulated between the consecutive moth peaks across different years were estimated at 504.05 ± 4.84. Seven generations were determined for pink bollworm in a cropping season, the length of which varied between 35 and 73 days in response to temperature. Pink bollworm population reached its peak during third generation which can be the target for management actions. The study provides essential information for developing pink bollworm management strategies under climate change.


Assuntos
Adaptação Biológica/fisiologia , Mariposas/crescimento & desenvolvimento , Previsões Demográficas/métodos , Temperatura , Animais , Comportamento Animal/fisiologia , Mudança Climática , Clima Desértico , Geografia , Gossypium/parasitologia , Índia/epidemiologia , Modelos Teóricos , Mariposas/classificação , Mariposas/fisiologia , Fenótipo , Dinâmica Populacional/tendências , Estações do Ano , Clima Tropical
10.
J Cell Physiol ; 236(8): 5921-5936, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-33481281

RESUMO

Plant bugs (Miridae species) have become major agricultural pests that cause increasing and severe economic damage. Plant-mediated RNA interference (RNAi) is emerging as an eco-friendly, efficient, and reliable strategy for pest management. In this study, we isolated and characterized a lethal gene of Apolygus lucorum and named it Apolygus lucorum LIM (AlLIM), which produced A. lucorum mortality rates ranging from 38% to 81%. Downregulation of the AlLIM gene expression in A. lucorum by injection of a double-stranded RNA (dsRNA) led to muscle structural disorganization that resulted in metamorphosis deficiency and increased mortality. Then we constructed a plant expression vector that enabled transgenic cotton to highly and stably express dsRNA of AlLIM (dsAlLIM) by Agrobacterium-mediated genetic transformation. In the field bioassay, dsAlLIM transgenic cotton was protected from A. lucorum damage with high efficiency, with almost no detectable yield loss. Therefore, our study successfully provides a promising genetically modified strategy to overpower A. lucorum attack.


Assuntos
Gossypium/parasitologia , Heterópteros/genética , Insetos/genética , Interferência de RNA/imunologia , Animais , Plantas/parasitologia
11.
Microb Ecol ; 81(2): 523-534, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32968841

RESUMO

Maintaining an adaptive seasonality is a basic ecological requisite for cold-blooded organism insects which usually harbor various symbionts. However, how coexisting symbionts coordinate in insects during seasonal progress is still unknown. The whitefly Bemisia tabaci in China harbors the obligate symbiont Portiera that infects each individual, as well as various facultative symbionts. In this study, we investigated whitefly populations in cucumber and cotton fields from May to December 2019, aiming to reveal the fluctuations of symbiont infection frequencies, symbiont coordination in multiple infected individuals, and host plants effects on symbiont infections. The results indicated that the facultative symbionts Hamiltonella (H), Rickettsia (R), and Cardinium (C) exist in field whiteflies, with single (H) and double (HC and HR) infections occurring frequently. Infection frequencies of Hamiltonella (always 100%) and Cardinium (29.50-34.38%) remained steady during seasonal progression. Rickettsia infection frequency in the cucumber whitefly population decreased from 64.47% in summer to 35.29% in winter. Significantly lower Rickettsia infection frequency (15.55%) was identified in cotton whitefly populations and was not subject to seasonal fluctuation. Nevertheless, Rickettsia had a significantly quantitative advantage in the symbiont community of whitefly individuals and populations from both cucumber and cotton field all through the seasons. Moreover, higher Portiera and Hamiltonella densities were found in HC and HR whitefly than in H whitefly, suggesting these symbionts may contribute to producing nutrients for their symbiont partners. These results provide ample cues to further explore the interactions between coexisting symbionts, the coevolutionary relationship between symbionts and host symbiont-induced effects on host plant use.


Assuntos
Hemípteros/microbiologia , Microbiota , Rickettsia/isolamento & purificação , Simbiose , Animais , Bactérias/classificação , Bactérias/genética , Bactérias/isolamento & purificação , China , Cucumis sativus/parasitologia , Gossypium/parasitologia , Interações Microbianas , Rickettsia/classificação , Rickettsia/genética , Estações do Ano
12.
Int J Mol Sci ; 21(22)2020 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-33187355

RESUMO

Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is an important agricultural pest worldwide. Uridine diphosphate (UDP)-glucuronosyltransferases (UGTs) are one of the largest and most ubiquitous groups of proteins. Because of their role in detoxification, insect UGTs are attracting increasing attention. In this study, we identified and analyzed UGT genes in B. tabaci MEAM1 to investigate their potential roles in host adaptation and reproductive capacity. Based on phylogenetic and structural analyses, we identified 76 UGT genes in the B. tabaci MEAM1 genome. RNA-seq and real-time quantitative PCR (RT-qPCR) revealed differential expression patterns of these genes at different developmental stages and in association with four host plants (cabbage, cucumber, cotton and tomato). RNA interference results of selected UGTs showed that, when UGT352A1, UGT352B1, and UGT354A1 were respectively silenced by feeding on dsRNA, the fecundity of B. tabaci MEAM1 was reduced, suggesting that the expressions of these three UGT genes in this species may be associated with host-related fecundity. Together, our results provide detailed UGTs data in B.tabaci and help guide future studies on the mechanisms of host adaptation by B.tabaci.


Assuntos
Glucuronosiltransferase/genética , Hemípteros/genética , Difosfato de Uridina/genética , Animais , Brassica/parasitologia , Cucumis sativus/parasitologia , Estudo de Associação Genômica Ampla , Gossypium/parasitologia , Proteínas de Insetos/genética , Lycopersicon esculentum/parasitologia , Filogenia , RNA de Cadeia Dupla/genética
13.
Sci Rep ; 10(1): 16840, 2020 10 08.
Artigo em Inglês | MEDLINE | ID: mdl-33033325

RESUMO

Evolution of resistance by pests reduces the benefits of transgenic crops that produce insecticidal proteins from Bacillus thuringiensis (Bt). Here we analyzed resistance to Bt toxin Cry1Ac in a field-derived strain of pink bollworm (Pectinophora gossypiella), a global pest of cotton. We discovered that the r14 allele of the pink bollworm cadherin gene (PgCad1) has a 234-bp insertion in exon 12 encoding a mutant PgCad1 protein that lacks 36 amino acids in cadherin repeat 5 (CR5). A strain homozygous for this allele had 237-fold resistance to Cry1Ac, 1.8-fold cross-resistance to Cry2Ab, and developed from neonate to adult on Bt cotton producing Cry1Ac. Inheritance of resistance to Cry1Ac was recessive and tightly linked with r14. PgCad1 transcript abundance in midgut tissues did not differ between resistant and susceptible larvae. Toxicity of Cry1Ac to transformed insect cells was lower for cells expressing r14 than for cells expressing wild-type PgCad1. Wild-type PgCad1 was transported to the cell membrane, whereas PgCad1 produced by r14 was not. In larval midgut tissue, PgCad1 protein occurred primarily on the brush border membrane only in susceptible larvae. The results imply r14 mediates pink bollworm resistance to Cry1Ac by reduced translation, increased degradation, and/or mislocalization of cadherin.


Assuntos
Antígenos CD/genética , Toxinas de Bacillus thuringiensis/farmacologia , Bacillus thuringiensis , Caderinas/genética , Resistência a Inseticidas/genética , Inseticidas/farmacologia , Mariposas/genética , Mariposas/microbiologia , Mutação , Controle Biológico de Vetores , Alelos , Animais , Éxons , Gossypium/parasitologia
14.
PLoS One ; 15(10): e0239910, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33002075

RESUMO

Transgenic cotton expressing Cry51Aa2.834_16 Bt toxin (hereafter referred to as MON 88702) has the potential to be an important tool for pest management due to its unique activity against tobacco thrips, Frankliniella fusca. Unlike other Bt toxins targeting lepidopteran cotton pests, MON 88702 does not cause direct mortality but has an antixenotic effect that suppresses F. fusca oviposition. Previous work has shown neonicotinoid seed treated (NST) crops have similar behavioral effects on thrips. This study used non-choice and common garden experiments to examine how the presence of MON 88702 cotton and soybean (another F. fusca host) with and without NSTs might alter F. fusca infestation distributions. In a no-choice environment, significant larval establishment differences were observed, with untreated soybean plants becoming most heavily infested. In choice experiments, plants expressing MON 88702 or were neonicotinoid treated had significantly lower larval establishment. Larval density decreased as dispersal distance increased, suggesting reproductive decisions were negatively related to distance from the release point. Understanding how F. fusca responds to MON 88702 in an environment where adults can choose among multiple host plants will provide valuable context for projections regarding design of MON 88702 resistance refuges. Reduced larval establishment on NST cotton and soybean suggests that area-wide use of NSTs could reduce the number of susceptible F. fusca generated in unstructured crop refuges for MON 88702. These results also suggest that although the presence of NST MON 88702 could suppress reproduction and resistance selection, over time this benefit could erode resulting in increased larval establishment on NST cotton and soybean due to increased frequency of neonicotinoid resistant F. fusca populations.


Assuntos
Gossypium/parasitologia , Inseticidas/farmacologia , Neonicotinoides/farmacologia , Doenças das Plantas/prevenção & controle , Tisanópteros/efeitos dos fármacos , Animais , Bacillus thuringiensis/genética , Toxinas Bacterianas/genética , Toxinas Bacterianas/metabolismo , Gossypium/genética , Oviposição/efeitos dos fármacos , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/parasitologia , Sementes/parasitologia , Soja/genética , Soja/parasitologia , Tisanópteros/patogenicidade , Tisanópteros/fisiologia
15.
J Biosci ; 452020.
Artigo em Inglês | MEDLINE | ID: mdl-32975236

RESUMO

The cotton bollworm, Helicoverpa armigera, is a highly polyphagous pest, causing enormous losses to various economically important crops. The identification and in vitro functional validation of target genes of a pest is a prerequisite to combat pest via host-mediated RNA interference (RNAi). In the present study, six hormonal biosynthesis genes of H. armigera were chosen and evaluated by feeding insect larvae with dsRNAs corresponding to each target gene, viz., juvenile hormone acid methyltransferase (HaJHAMT), prothoracicotropic hormone (HaPTTH), pheromone biosynthesis-activating peptide (HaPBAP), molt regulating transcription factor (HaHR3), activated protein 4 (HaAP-4) and eclosion hormone precursor (HaEHP). The loss of function phenotypes for these hormonal genes were observed by releasing second instar larvae on to artificial diet containing target gene-specific dsRNAs. Ingestion of dsRNAs resulted in mortality ranging from 60% to 90%, reduced larval weight, phenotypic deformities and delayed pupation. The quantitative real-time PCR (qRT-PCR) analysis showed that the target gene transcript levels were decreased drastically (31% to 77%) as compared to control or unrelated control (GFP-dsRNA), and correlated well with the mortality and developmental defects of larvae. Also, a comparison of the silencing efficacy of un-diced long HaPTTH -dsRNAwith RNase III diced HaPTTH-dsRNA (siRNAs) revealed that long dsRNAs were more efficient in silencing the target gene. These results indicated that the hormonal biosynthesis genes have varied sensitivity towards RNAi and could be the vital targets for insect resistance in crop plants like cotton which are infested by H. armigera.


Assuntos
Controle de Insetos/métodos , Proteínas de Insetos/antagonistas & inibidores , Larva/genética , Mariposas/genética , Interferência de RNA , RNA Mensageiro/genética , Animais , Regulação da Expressão Gênica no Desenvolvimento , Genes Reporter , Gossypium/parasitologia , Proteínas de Fluorescência Verde/antagonistas & inibidores , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Hormônios de Inseto/antagonistas & inibidores , Hormônios de Inseto/genética , Hormônios de Inseto/metabolismo , Proteínas de Insetos/genética , Proteínas de Insetos/metabolismo , Larva/crescimento & desenvolvimento , Larva/metabolismo , Longevidade/genética , Metiltransferases/antagonistas & inibidores , Metiltransferases/genética , Metiltransferases/metabolismo , Mariposas/crescimento & desenvolvimento , Mariposas/metabolismo , Neuropeptídeos/antagonistas & inibidores , Neuropeptídeos/genética , Neuropeptídeos/metabolismo , RNA de Cadeia Dupla/genética , RNA de Cadeia Dupla/metabolismo , RNA Mensageiro/antagonistas & inibidores , RNA Mensageiro/metabolismo
16.
J Chem Ecol ; 46(10): 967-977, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32979116

RESUMO

In solitary endoparasitoids, oviposition in a host previously parasitized by a conspecific (superparasitism) leads to intraspecific competition, resulting in the elimination of all but one parasitoid offspring. Therefore, avoidance of parasitized hosts presents a strong selective advantage for such parasitoid species. Parasitoids use herbivore-induced plant volatiles (HIPVs) to find their hosts. In this study, we evaluated the ability of Microplitis croceipes (Hymenoptera: Braconidae) to discriminate between unparasitized and parasitized Heliothis virescens (Lepidoptera: Noctuidae) larvae using cotton plant odors as cues. A combination of behavioral and analytical techniques were used to test two hypotheses: (i) parasitoids will show preference for plant odors induced by unparasitized hosts over odors induced by parasitized hosts, and (ii) the parasitism status of herbivores affects HIPV emission in plants. Heliothis virescens larvae were parasitized for varying durations (0, 2 and 6-days after parasitism (DAP)). In four-choice olfactometer bioassays, female M. croceipes showed greater attraction to plant odors induced by unparasitized hosts compared to plant odors induced by parasitized hosts (2 and 6-DAP). Comparative gas chromatography-mass spectrometry analyses of cotton volatiles indicated reduced emission of 10 out of 21 identified compounds from plants infested by parasitized hosts compared with plants infested by unparasitized hosts. The results suggest that changes in plant volatile emission due to the parasitism status of infesting herbivores affect recruitment of parasitoids. Avoidance of superparasitism using plant odors optimizes host foraging in M. croceipes, and this strategy may be widespread in solitary parasitoid species.


Assuntos
Gossypium/parasitologia , Interações Hospedeiro-Parasita , Lepidópteros/crescimento & desenvolvimento , Compostos Orgânicos Voláteis/farmacologia , Vespas/fisiologia , Animais , Cromatografia Gasosa-Espectrometria de Massas , Gossypium/química , Herbivoria , Larva/efeitos dos fármacos , Larva/crescimento & desenvolvimento , Lepidópteros/efeitos dos fármacos , Oviposição , Compostos Orgânicos Voláteis/análise
17.
Toxins (Basel) ; 12(9)2020 08 28.
Artigo em Inglês | MEDLINE | ID: mdl-32872277

RESUMO

Insecticidal toxins from Bacillus thuringiensis (Bt) are valuable tools for pest management worldwide, contributing to the management of human disease insect vectors and phytophagous insect pests of agriculture and forestry. Here, we report the effects of dual and triple Bt toxins expressed in transgenic cotton cultivars on the fitness and demographic performance of Helicoverpa zea (Boddie)-a noctuid pest, known as cotton bollworm and corn earworm. Life-history traits were determined for individuals of three field populations from a region where H. zea overwintering is likely. Triple-gene Bt cotton cultivars that express Cry and Vip3Aa toxins killed 100% of the larvae in all populations tested. In contrast, dual-gene Bt cotton that express Cry1Ac+Cry1F and Cry1Ac+Cry2Ab allowed population growth with the intrinsic rate of population growth (rm) 38% lower than on non-Bt cotton. The insects feeding on Bt cotton plants that express Cry1Ac+Cry2Ab, Cry1Ac+Cry1F, or Cry1Ab+Cry2Ae exhibited reduced larval weight, survival rate, and increased development time. Additionally, fitness parameters varied significantly among the insect populations, even on non-Bt cotton plants, likely because of their different genetic background and/or previous Bt toxin exposure. This is the first report of the comparative fitness of H. zea field populations on dual-gene Bt cotton after the recent reports of field resistance to certain Bt toxins. These results document the population growth rates of H. zea from an agricultural landscape with 100% Bt cotton cultivars. Our results will contribute to the development and validation of resistance management recommendations.


Assuntos
Toxinas de Bacillus thuringiensis/metabolismo , Proteínas de Bactérias/metabolismo , Endotoxinas/metabolismo , Gossypium/parasitologia , Proteínas Hemolisinas/metabolismo , Mariposas/metabolismo , Controle Biológico de Vetores , Plantas Geneticamente Modificadas/parasitologia , Animais , Toxinas de Bacillus thuringiensis/genética , Proteínas de Bactérias/genética , Endotoxinas/genética , Feminino , Regulação da Expressão Gênica de Plantas , Aptidão Genética , Gossypium/genética , Gossypium/metabolismo , Proteínas Hemolisinas/genética , Masculino , Mariposas/embriologia , Mariposas/genética , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/metabolismo , Dinâmica Populacional , Fatores de Tempo
18.
PLoS One ; 15(8): e0237318, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32804952

RESUMO

The mirid bug Lygus pratensis is an important pest of cotton, and is primarily managed through insecticide application. In this study, conducted in Xinjiang (China), we assessed the relative attractiveness of sunflower (Helianthus annuus) to L. pratensis adults in local cotton plots from 2015-2016 and quantified the associated contribution of inter-planted sunflower strips to suppress field-level L. pratensis populations from 2016-2017. Field-plot trials showed that among six combinations of two sunflower varieties (XKZ6 and SH363) and three planting dates (early-, middle- and late-planted), adult abundance of L. pratensis was highest on early-planted XKZ6 and attained 3.7-5.8 times higher levels than in neighboring cotton plots. In commercial cotton fields, the combined deployment of sunflower strips at field edges and the periodic application of insecticides directed to those strips was found to (1) reduce the mean abundance of L. pratensis population on cotton by 41.9-44.0%, (2) lower the rate of cotton leaf damage by 27.3-30.6% and boll damage by 44.8-46.0%, and (3) increase the number of mature bolls by 7.5%-8.0%. Our work emphasizes how sunflower can be an effective trap crop for L. pratensis and that the establishment of sunflower strips could contribute to its effective and environmentally-sound management in cotton crops.


Assuntos
Proteção de Cultivos/métodos , Produtos Agrícolas/parasitologia , Gossypium/parasitologia , Helianthus/parasitologia , Heterópteros/fisiologia , Animais , China , Comportamento Alimentar , Folhas de Planta/parasitologia
19.
PLoS One ; 15(7): e0235344, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32628728

RESUMO

A Glycine max (soybean) hemicellulose modifying gene, xyloglucan endotransglycoslase/hydrolase (XTH43), has been identified as being expressed within a nurse cell known as a syncytium developing within the soybean root undergoing the process of defense to infection by the parasitic nematode, Heterodera glycines. The highly effective nature of XTH43 overexpression in suppressing H. glycines parasitism in soybean has led to experiments examining whether the heterologous expression of XTH43 in Gossypium hirsutum (upland cotton) could impair the parasitism of Meloidogyne incognita, that form a different type of nurse cell called a giant cell that is enclosed within a swollen root structure called a gall. The heterologous transgenic expression of XTH43 in cotton resulted in an 18% decrease in the number of galls, 70% decrease in egg masses, 64% decrease in egg production and a 97% decrease in second stage juvenile (J2) production as compared to transgenic controls. The heterologous XTH43 expression does not significantly affect root mass. The results demonstrate XTH43 expression functions effectively in impairing the development of M. incognita at numerous life cycle stages occurring within the cotton root. The experiments reveal that there are highly conserved aspects of the defense response of G. max that can function effectively in G. hirsutum to impair M. incognita having a different method of parasitism.


Assuntos
Glicosiltransferases/genética , Gossypium/parasitologia , Doenças das Plantas/prevenção & controle , Proteínas de Soja/genética , Soja/enzimologia , Tylenchoidea , Animais , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Glicosiltransferases/metabolismo , Gossypium/genética , Doenças das Plantas/parasitologia , Raízes de Plantas/parasitologia , Plantas Geneticamente Modificadas , Proteínas de Soja/metabolismo , Soja/genética
20.
Proc Natl Acad Sci U S A ; 117(29): 16928-16937, 2020 07 21.
Artigo em Inglês | MEDLINE | ID: mdl-32636269

RESUMO

Whereas most of the arthropod-borne animal viruses replicate in their vectors, this is less common for plant viruses. So far, only some plant RNA viruses have been demonstrated to replicate in insect vectors and plant hosts. How plant viruses evolved to replicate in the animal kingdom remains largely unknown. Geminiviruses comprise a large family of plant-infecting, single-stranded DNA viruses that cause serious crop losses worldwide. Here, we report evidence and insight into the replication of the geminivirus tomato yellow leaf curl virus (TYLCV) in the whitefly (Bemisia tabaci) vector and that replication is mainly in the salivary glands. We found that TYLCV induces DNA synthesis machinery, proliferating cell nuclear antigen (PCNA) and DNA polymerase δ (Polδ), to establish a replication-competent environment in whiteflies. TYLCV replication-associated protein (Rep) interacts with whitefly PCNA, which recruits DNA Polδ for virus replication. In contrast, another geminivirus, papaya leaf curl China virus (PaLCuCNV), does not replicate in the whitefly vector. PaLCuCNV does not induce DNA-synthesis machinery, and the Rep does not interact with whitefly PCNA. Our findings reveal important mechanisms by which a plant DNA virus replicates across the kingdom barrier in an insect and may help to explain the global spread of this devastating pathogen.


Assuntos
Begomovirus/fisiologia , DNA Polimerase III/metabolismo , Hemípteros/virologia , Proteínas de Insetos/metabolismo , Insetos Vetores/virologia , Replicação Viral , Animais , Begomovirus/genética , DNA Polimerase III/genética , Gossypium/parasitologia , Gossypium/virologia , Hemípteros/patogenicidade , Interações Hospedeiro-Patógeno , Proteínas de Insetos/genética , Insetos Vetores/patogenicidade , Glândulas Salivares/metabolismo , Glândulas Salivares/virologia
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