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1.
Int J Mol Sci ; 22(7)2021 Mar 24.
Artigo em Inglês | MEDLINE | ID: mdl-33805017

RESUMO

Identification of novel agents for bladder cancer treatment is highly desirable due to the high incidence of tumor recurrence and the risk of progression to muscle-invasive disease. The key feature of the cholesterol-dependent toxin listeriolysin O mutant (LLO Y406A) is its preferential activity at pH 5.7, which could be exploited either directly for selective targeting of cancer cells or the release of accumulated therapeutics from acidic endosomes. Therefore, our goal was to compare the cytotoxic effect of LLO Y406A on cancer cells (RT4) and normal urothelial cells (NPU), and to identify which cell membranes are the primary target of LLO Y406A by viability assays, life-cell imaging, fluorescence, and electron microscopy. LLO Y406A decreased viability, altered cell morphology, provoked membrane blebbing, and induced apoptosis in RT4 cells, while it did not affect NPU cells. LLO Y406A did not cause endosomal escape in RT4 cells, while the plasma membrane of RT4 cells was revealed as the primary target of LLO Y406A. It has been concluded that LLO Y406A has the ability to selectively eliminate cancer urothelial cells through pore-forming activity at the plasma membrane, without cytotoxic effects on normal urothelial cells. This promising selective activity merits further testing as an anti-cancer agent.


Assuntos
Antineoplásicos/toxicidade , Toxinas Bacterianas/toxicidade , Membrana Celular/efeitos dos fármacos , Proteínas de Choque Térmico/toxicidade , Proteínas Hemolisinas/toxicidade , Neoplasias da Bexiga Urinária/metabolismo , Urotélio/efeitos dos fármacos , Animais , Toxinas Bacterianas/genética , Cálcio/metabolismo , Linhagem Celular Tumoral , Membrana Celular/metabolismo , Células Cultivadas , Endossomos/efeitos dos fármacos , Endossomos/metabolismo , Proteínas de Choque Térmico/genética , Proteínas Hemolisinas/genética , Humanos , Mutação , Suínos , Urotélio/metabolismo
2.
GM Crops Food ; 12(1): 292-302, 2021 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-33648412

RESUMO

Gossypium arboreum (Desi Cotton) holds a special place in cotton industry because of its inherent ability to withstand drought, salinity, and remarkable resistance to sucking pests and cotton leaf curl virus. However, it suffers yield losses due to weeds and bollworm infestation. Genetic modification of G. arboreum variety FBD-1 was attempted in the current study to combat insect and weedicide resistance by incorporating cry1Ac, cry2A and cp4-EPSPS genes under control of 35S promoter in two different cassettes using kanamycin and GUS as markers through Agrobacterium-mediated shoot apex cut method of cotton transformation. The efficiency of transformation was found to be 1.57%. Amplification of 1700 bp for cry1Ac, 167 bp for cry2A and 111 bp for cp4-EPSPS confirmed the presence of transgenes in cotton plants. The maximum mRNA expression of cry1Ac and cp4-EPSPS was observed in transgenic cotton line L3 while minimum in transgenic cotton line L1. The maximum protein concentrations of Cry1Ac, Cry2A and Cp4-EPSPS of 3.534 µg g-1, 2.534 µg g-1 and 3.58 µg-g-1 respectively were observed for transgenic cotton line L3 as compared to control cotton line. On leaf-feed-based insect bioassay, almost 99% mortality was observed for Helicoverpa armigera on the transgenic cotton plant (L3). It completely survived the 1900 ml hectare-1 glyphosate spray assay as compared to non-transgenic cotton plants. The necrotic spots appeared on the third day, leading to the complete death of control plants on the fifth day of assay. The successful multiple gene-stacking in G. arboreum FBD-1 variety could be further used for qualitative improvement of cotton fiber through plant breeding techniques.


Assuntos
Gossypium , Mariposas , Animais , Proteínas de Bactérias/genética , Endotoxinas , Gossypium/genética , Proteínas Hemolisinas/genética , Melhoramento Vegetal , Plantas Geneticamente Modificadas
3.
GM Crops Food ; 12(1): 303-314, 2021 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-33648419

RESUMO

The safety of transgenic Bt rice containing bacteria-derived mCry1Ac gene from Bacillus thuringiensis (Bt) was assessed by conducting field trials at two locations for two consecutive years in South Korea, using the near-isogenic line comparator rice cultivar ('Ilmi', non-Bt rice) and four commercial cultivars as references. Compositional analyses included measurement of proximates, minerals, amino acids, fatty acids, vitamins, and antinutrients. Significant differences between Bt rice and non-Bt rice were detected; however, all differences were within the reference range. The statistical analyses, including analysis of % variability, analysis of similarities (ANOISM), similarity percentage (SIMPER) analysis, and permutational multivariate analysis of variance (PERMANOVA) were performed to study factors contributing to compositional variability. The multivariate analyses revealed that environmental factors more influenced rice components' variability than by genetic factors. This approach was shown to be a powerful method to provide meaningful evaluations between Bt rice and its comparators. In this study, Bt rice was proved to be compositionally equivalent to conventional rice varieties through multiple statistical methods.


Assuntos
Bacillus thuringiensis , Oryza , Animais , Bacillus thuringiensis/genética , Proteínas de Bactérias/genética , Endotoxinas/genética , Proteínas Hemolisinas/genética , Insetos , Oryza/genética , Plantas Geneticamente Modificadas/genética , República da Coreia
4.
Ecotoxicol Environ Saf ; 212: 111967, 2021 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-33524911

RESUMO

Non-target effects of genetically engineered (GE) plants on aquatic Daphnia magna have been studied by feeding the species with different maize materials containing insecticidal Cry proteins from Bacillus thuringiensis (Bt). The results of those studies were often difficult to interpret, because only one GE plant was compared to one related non-GE control. In such a setting, effects of the Cry proteins cannot be distinguished from plant background effects, in particular when the test species is nutritionally stressed. In the present study, we tested the suitability of three different maize materials, i.e., flour, leaves and pollen, from five diverse non-GE maize lines (including EXP 258, a breeding line that is closely related to a SmartStax Bt maize) as exclusive food sources for D. magna. The parameters recorded included survival, sublethal endpoints such as body size, number of moltings to first offspring, time to first offspring, number of individuals in first clutch, total number of clutches, total number of offspring, average number of offspring per clutch, and population measures such as net reproductive rate R0, generation time T and intrinsic rate of increase rm. The results showed that D. magna can survive, grow and reproduce when fed only maize materials, although the performance was poorer than when fed algae, which indicates nutritional stress. Large differences in life table and population parameters of D. magna were observed among the different maize lines. Our results suggest that confounding effects caused by nutritional stress and plant background might explain some of the conflicting results previously published on the effects of Bt crops on D. magna. Using 95% confidence intervals for the means of the five maize lines for all measured parameters of D. magna performance in our study, we captured the natural range of variation. This information is useful for the interpretation of observed differences in D. magna performance between a GE plant and its non-GE comparator as it helps judging whether observed effects are of biological relevance. If differences between a GE and comparator line are observed and their biological relevance needs to be assessed in future risk assessments of GE maize, 1) the data on natural variation of the different parameters generated by previous studies can be informative (e.g. data from our study for maize fed D. magna); 2) for additional experiments the inclusion of multiple unrelated non-GE comparators should be considered; In addition, it should be taken into account that nutritional stress can affect the outcome of the study.


Assuntos
Daphnia/fisiologia , Plantas Geneticamente Modificadas/fisiologia , Zea mays/fisiologia , Animais , Bacillus thuringiensis/metabolismo , Proteínas de Bactérias/metabolismo , Produtos Agrícolas/metabolismo , Daphnia/efeitos dos fármacos , Endotoxinas/metabolismo , Farinha , Proteínas Hemolisinas/genética , Inseticidas/farmacologia , Melhoramento Vegetal , Folhas de Planta/metabolismo , Plantas Geneticamente Modificadas/metabolismo , Plantas Geneticamente Modificadas/toxicidade , Pólen , Medição de Risco , Zea mays/metabolismo
5.
Pest Manag Sci ; 77(5): 2367-2374, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33415822

RESUMO

BACKGROUND: Helicoverpa zea is managed with foliar applications of chlorantraniliprole in cotton varieties that do not express the Vip3Aa19 toxin in the US Cotton Belt. Foliar insecticides and Bt could interact to influence larval susceptibility. Therefore, it has been suggested that chlorantraniliprole can be used as a tool for Bt resistance management. We designed field and laboratory studies to test the hypothesis that the interaction of Bt toxin and chlorantraniliprole application would result in lower H. zea larval survival when compared to the individual effect of Bt or chlorantraniliprole alone. We also tested for these interactions over time, since chlorantraniliprole residual has not been studied in cotton. RESULTS: Results from two field experiments and two laboratory experiments were similar. We found no interactions with Bt and chlorantraniliprole using data not corrected for natural mortality in untreated plots, indicating that these factors did not interact to influence survival. Moreover, we found that Bt and chlorantraniliprole did not interact to influence larval weight and instar. Chlorantraniliprole had lethal and sublethal effects on H. zea larval growth parameters feeding on cotton leaves up to 22 days after application, the final time period that we tested. Finally, concentration of chlorantraniliprole in the leaf was associated with larval survival for the duration of this study, but not larval growth or instar. CONCLUSION: Our findings complement the recommendation to use chlorantraniliprole for managing H. zea in cotton, given its long-residual effects. However, the utility of chlorantraniliprole as a Bt-resistance management tool for H. zea remains unclear. © 2021 Society of Chemical Industry.


Assuntos
Bacillus thuringiensis , Mariposas , Animais , Bacillus thuringiensis/genética , Proteínas de Bactérias/genética , Endotoxinas , Gossypium/genética , Proteínas Hemolisinas/genética , Larva , Mariposas/genética , Plantas Geneticamente Modificadas , Zea mays/genética , ortoaminobenzoatos
6.
PLoS Pathog ; 17(1): e1009199, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-33465145

RESUMO

The insecticidal Cry11Aa and Cyt1Aa proteins are produced by Bacillus thuringiensis as crystal inclusions. They work synergistically inducing high toxicity against mosquito larvae. It was proposed that these crystal inclusions are rapidly solubilized and activated in the gut lumen, followed by pore formation in midgut cells killing the larvae. In addition, Cyt1Aa functions as a Cry11Aa binding receptor, inducing Cry11Aa oligomerization and membrane insertion. Here, we used fluorescent labeled crystals, protoxins or activated toxins for in vivo localization at nano-scale resolution. We show that after larvae were fed solubilized proteins, these proteins were not accumulated inside the gut and larvae were not killed. In contrast, if larvae were fed soluble non-toxic mutant proteins, these proteins were found inside the gut bound to gut-microvilli. Only feeding with crystal inclusions resulted in high larval mortality, suggesting that they have a role for an optimal intoxication process. At the macroscopic level, Cry11Aa completely degraded the gastric caeca structure and, in the presence of Cyt1Aa, this effect was observed at lower toxin-concentrations and at shorter periods. The labeled Cry11Aa crystal protein, after midgut processing, binds to the gastric caeca and posterior midgut regions, and also to anterior and medium regions where it is internalized in ordered "net like" structures, leading finally to cell break down. During synergism both Cry11Aa and Cyt1Aa toxins showed a dynamic layered array at the surface of apical microvilli, where Cry11Aa is localized in the lower layer closer to the cell cytoplasm, and Cyt1Aa is layered over Cry11Aa. This array depends on the pore formation activity of Cry11Aa, since the non-toxic mutant Cry11Aa-E97A, which is unable to oligomerize, inverted this array. Internalization of Cry11Aa was also observed during synergism. These data indicate that the mechanism of action of Cry11Aa is more complex than previously anticipated, and may involve additional steps besides pore-formation activity.


Assuntos
Aedes/efeitos dos fármacos , Sinergismo Farmacológico , Endotoxinas/metabolismo , Trato Gastrointestinal/efeitos dos fármacos , Proteínas Hemolisinas/metabolismo , Inseticidas/metabolismo , Larva/efeitos dos fármacos , Aedes/metabolismo , Animais , /toxicidade , Proteínas de Bactérias , Endotoxinas/genética , Endotoxinas/toxicidade , Trato Gastrointestinal/metabolismo , Proteínas Hemolisinas/genética , Proteínas Hemolisinas/toxicidade , Inseticidas/toxicidade , Larva/metabolismo , Ligação Proteica
7.
Ecotoxicol Environ Saf ; 208: 111680, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33396012

RESUMO

The widespread commercialization of genetically modified (GM) cotton makes it important to assess the potential impact of this recombinant crop on non-target organisms. As important natural enemies of cotton field predators, green lacewing Chrysoperla sinica larvae are exposed to Bt insecticidal proteins expressed by GM cotton by feeding on herbivorous pests, and adults are directly exposed to Bt proteins by cotton pollen consumption. However, potential impacts of transgenic Bt cotton on C. sinica remain unclear. In this study, we evaluated the effects of two transgenic cotton varieties, CCRI41 and CCRI45, which express Cry1Ac (Bt toxin) and CpTI (Cowpea Trypsin Inhibitor), on C. sinica larvae and adults. After being fed with cotton aphids Aphis gossypii reared on transgenic cotton, the survival rate, developmental duration, pupation rate, and emergence rate of larvae were not adversely affected. After being fed two types of transgenic cotton pollen, the 7-day weight of adults and the preoviposition period and the cumulative oviposition of females were not significantly different from control specimen. Taken together, these results indicate that the potential risks of the two tested GM cotton varieties for the predator C. sinica are negligible. CAPSULE: Our study indicated that GM cotton varieties CCRI41 and CCRI45 have no adverse effects on insect predator C. sinica.


Assuntos
/genética , Gossypium/crescimento & desenvolvimento , Insetos/efeitos dos fármacos , Larva/efeitos dos fármacos , Plantas Geneticamente Modificadas/crescimento & desenvolvimento , Inibidores da Tripsina/metabolismo , Animais , Endotoxinas/metabolismo , Feminino , Gossypium/genética , Gossypium/metabolismo , Proteínas Hemolisinas/genética , Insetos/metabolismo , Larva/metabolismo , Controle Biológico de Vetores , Plantas Geneticamente Modificadas/metabolismo , Pólen/genética , Pólen/metabolismo
8.
Pest Manag Sci ; 77(4): 1963-1970, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33314557

RESUMO

BACKGROUND: Pyramided Bacillus thuringiensis (Bt) crops could delay insect resistance development by expressing multiple distinct Bt proteins to manage the same insect pest. The efficacy of pyramiding strategy for resistance management could be jeopardized by positive cross-resistance, which is defined as insects showing resistance to one Bt protein also exhibiting resistance to other Bt proteins. The fall armyworm, Spodoptera frugiperda, is a destructive agricultural pest and target of Vip3Aa. In this study, we evaluate the cross-resistance of Vip3Aa resistance in S. frugiperda to Bt cotton and corn plants, as well as purified Bt proteins. RESULTS: Diet bioassay showed that Vip3Aa-resistant (RR), -heterozygous (RS), and -susceptible (SS) insects of S. frugiperda performed similarly against Cry2Ab2 purified protein. The data also indicated that genotypes RR and RS were more susceptible to Cry1F and Cry2Ae purified proteins relative to SS. The diet bioassays suggested that resistance to Vip3Aa does not confer any positive cross-resistance to Cry1F, Cry2Ae or Cry2Ab2 in S. frugiperda. The plant bioassay indicated that the S. frugiperda resistance to Vip3Aa conferred no cross-resistance to corn and no cross-crop resistance to cotton plants expressing Cry1 and/or Cry2 proteins. CONCLUSION: These findings indicate that a lack of positive cross-resistance to Cry1 and Cry2 proteins favors pyramiding strategy for managing S. frugiperda resistance to Vip3Aa protein. © 2020 Society of Chemical Industry.


Assuntos
Bacillus thuringiensis , Proteínas de Bactérias , Animais , Bacillus thuringiensis/genética , Proteínas de Bactérias/genética , Endotoxinas/farmacologia , Proteínas Hemolisinas/genética , Proteínas Hemolisinas/farmacologia , Resistência a Inseticidas/genética , Larva/genética , Plantas Geneticamente Modificadas/genética , Spodoptera/genética , Zea mays/genética
9.
Pest Manag Sci ; 77(4): 2142-2150, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33336541

RESUMO

BACKGROUND: Extensive planting of transgenetic Bacillus thuringiensis crops has driven the evolution of pest resistance to Cry1Ac. Adjustment of cropping structures has promoted further outbreak of Helicoverpa armigera in China. To control this pest, a combination of pyramiding RNA interference (RNAi) and Cry2Ab is considered a promising strategy for countering cross-resistance and enhancing the toxicity of Cry2Ab to cotton bollworm. We explored the possibility of using calcineurin (CAN) as a target RNAi gene, because it is involved in cotton bollworm responses to the toxicity of Cry2Ab. RESULTS: Cry2Ab treatment led to a significant increase in HaCAN mRNA level and HaCAN activity. Suppression of HaCAN activity due to RNAi-mediated knockdown of HaCAN increased the susceptibility of midgut cells to Cry2Ab. The increase in HaCAN activity shown by heterologous expression of HaCAN reduced the cytotoxicity of Cry2Ab to Sf9 cells. Moreover, ingestion of HaCAN-specific inhibitor FK506 increased the toxicity of Cry2Ab in larvae. Interestingly, HaCAN does not function as a Cry2Ab direct binding protein that participates in Cry2Ab toxicity. CONCLUSIONS: The results in this study provide evidence that suppression of HaCAN not only affected the development of the cotton bollworm, but also enhanced the toxicity of Cry2Ab to the pest. HaCAN is therefore an important candidate gene in cotton bollworm that can be targeted for pest control when the pest infests RNAi+Cry2Ab crops. Meanwhile, the mechanism of action of HaCAN in Cry2Ab toxicity suggested that protein dephosphorylation was involved. © 2020 Society of Chemical Industry.


Assuntos
Bacillus thuringiensis , Mariposas , Animais , Proteínas de Bactérias/genética , Calcineurina/genética , China , Endotoxinas/genética , Endotoxinas/farmacologia , Gossypium , Proteínas Hemolisinas/genética , Resistência a Inseticidas , Larva/genética , Mariposas/genética , Plantas Geneticamente Modificadas
10.
Pest Manag Sci ; 77(4): 2106-2113, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33350567

RESUMO

BACKGROUND: Using natural populations of Helicoverpa zea from Arizona, we tested the hypotheses that gene flow between Bacillus thuringiensis (Bt) plants and non-Bt plants in a seed mixture of 10% non-Bt corn and 90% Bt corn producing Cry1A.105 and Cry2Ab reduces larval performance on ears from non-Bt plants, or increases performance on ears from Bt plants. RESULTS: Gene flow was not detected in blocks of non-Bt or Bt corn but was extensive in seed mixtures. Analyses of larval weight and abundance over a period of 3 to 4 weeks did not indicate consistent effects of gene flow on development rate and survival. However for non-Bt plants, the ear area damaged and percentage of ears with exit holes were significantly lower in the seed mixtures than blocks. By contrast, the percentage of ears with exit holes and ear damage did not differ significantly between the seed mixtures and blocks for Bt plants. Nearly 100% of the ears were damaged and the damaged area was substantial, showing that H. zea is a major ear-feeding pest in Arizona. Relative to non-Bt corn, the pyramided Bt corn did not significantly reduce the percentage of damaged ears and only reduced the ear area damaged by 21 to 39%, indicating that H. zea may have evolved resistance to Cry1A.105, Cry2Ab, or both. CONCLUSIONS: Our results indicate that gene flow between Bt and non-Bt plants in seed mixtures reduced effective refuge size, and that block refuges may be needed to manage the evolution of H. zea resistance to Bt corn in Arizona. © 2020 Society of Chemical Industry.


Assuntos
Bacillus thuringiensis , Mariposas , Animais , Arizona , Bacillus thuringiensis/genética , Proteínas de Bactérias/genética , Endotoxinas/genética , Fluxo Gênico , Proteínas Hemolisinas/genética , Resistência a Inseticidas/genética , Mariposas/genética , Controle Biológico de Vetores , Plantas Geneticamente Modificadas/genética , Sementes , Zea mays/genética
11.
GM Crops Food ; 12(1): 47-56, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-32862762

RESUMO

The sugarcane (Saccharum X officinarum) is one of the most important crops used to produce sugar and raw material for biofuel in the world. One of the main causes for sucrose content and yield losses is the attack by insect. In this investigation, cry1Ac gene was introduced into sugarcane variety GT54-9(C9) using the Agrobacterium tumefaciens transformation method for transgenic sugarcane production presenting insect-resistance. The A. tumefaciens strain GV1303 including pARTcry1Ac vector was used for the production of transformed sugarcane. The Bacillus thuringiensis cry gene were successfully used to produce transgenic plants used for the improvement of both agronomic efficiency and product quality by acquiring insect resistance. PCR and Southern hybridization techniques were used to confirm the cry1Ac gene incorporation into sugarcane genome. Transformation percentage was 22.2% using PCR analysis with specific primers for cry1Ac and npt-II (Neomycin phosphotransferase) genes. The expression of cry1Ac gene was determined using reverse transcriptase polymerase chain reaction (RT-PCR), QuickStix test, and insect bioassays. Bioassays for transformed sugarcane plants showed high level of toxicity to Sesamia cretica giving 100% mortality of the larvae. Sugarcane insect resistance was improved significantly by using cry1Ac gene transformation.


Assuntos
Saccharum/genética , Agrobacterium , Animais , Proteínas de Bactérias/genética , Endotoxinas , Proteínas Hemolisinas/genética , Plantas Geneticamente Modificadas
12.
GM Crops Food ; 12(1): 192-211, 2021 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-33380258

RESUMO

Evolution of resistance to genetically modified Bacillus thuringiensis (Bt) crops in pest populations is a major threat to the sustainability of the technology. Incidents of field resistance that have led to control problems of Bt crops or significantly reduced susceptibility of individual Bt proteins in pyramided plants have increased dramatically across the world, especially in recent years. Analysis of globally published data showed that 61.5% and 60.0% of the cases of resistance with major alleles that allowed homozygous resistant genotypes to survival on Bt crops were functionally non-recessive and did not involve fitness costs, respectively. Dominance levels (DFLs) measured on Bt plants ranged from -0.02 to 1.56 with a mean (± sem) of 0.35 ± 0.13 for the 13 cases of single-gene resistance to Bt plants that have been evaluated. Among these, all six cases with field control problems were functionally non-recessive with a mean DFL of 0.63 ± 0.24, which was significantly greater than the DFL (0.11 ± 0.07) of the seven cases without field resistance. In addition, index of fitness costs (IFC) of major resistance was calculated for each case based on the fitness of resistant (R'R') and heterozygous (R'S') genotypes on non-Bt plants divided by the fitness of their susceptible (S'S') counterparts. The estimated IFCs for 15 cases of single-gene resistance were similar for R'R' and R'S', and for the cases with and without field resistance; and the values averaged 1.10 ± 0.12 for R'R' and 1.20 ± 0.18 for R'S'. Limited published data suggest that resistance of insects to dual/multiple-gene Bt crops is likely to be more recessive than the related single-gene resistance, but their IFCs are similar. The quantitative analysis of the global data documents that the prevalence of non-recessive resistance has played an essential role in the widespread evolution of resistance to Bt crops, while the lack of fitness costs is apparently not as critical as the non-recessive resistance. The results suggest that planting of 'high dose' traits is an effective method for Bt crop IRM and more comprehensive management strategies that are also effective for functionally non-recessive resistance should be deployed.


Assuntos
Bacillus thuringiensis , Animais , Bacillus thuringiensis/genética , Proteínas de Bactérias/genética , Produtos Agrícolas/genética , Endotoxinas , Proteínas Hemolisinas/genética , Insetos , Resistência a Inseticidas/genética , Controle Biológico de Vetores , Plantas Geneticamente Modificadas
13.
Ecotoxicol Environ Saf ; 207: 111215, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-32927159

RESUMO

Field cultivation of Genetically Modified (GM) Bt-plants has a potential environmental risk toward non-target Lepidoptera (NTLs) larvae through the consumption of Bt-maize pollen. The Bt-maize Cry protein targeting Lepidoptera species detrimental to the crop is also expressed in pollen which is dispersed by wind and can thus reach habitats of NTLs. To better assess the current ecological risk of Bt-maize at landscape scales, we developed a spatially-explicit exposure-hazard model considering (i) the dynamics of pollen dispersal obtained by convolving GM plants emission with a dispersal kernel and (ii) a toxicokinetic-toxicodynamic (TKTD) model accounting for the impact of toxin ingestion on individual lethal effects. We simulated the model using real landscape observations in Catalonia (Spain): GM-maize locations, flowering dates, rainfall time series and larvae emergence date of the European peacock butterfly Aglais io. While in average, the additional mortality appears to be negligible, we show significant additional mortality at sub-population level, with for instance a mortality higher than 40% within the 10m for the 10% most Bt-sensitive individuals. Also, using Pareto optimality we capture the best trade-off between isolation distance and additional mortality: up to 50 m are required to significantly buffer Bt-pollen impact on NTLs survival at the individual level. Our study clears up the narrow line between diverging conclusions: those claiming no risk by only looking at the average regional effect of Bt on NTLs survival and those pointing out a significant threaten when considering the variability of individuals mortality.


Assuntos
/toxicidade , Borboletas/fisiologia , Endotoxinas/toxicidade , Proteínas Hemolisinas/toxicidade , Plantas Geneticamente Modificadas/fisiologia , Zea mays/fisiologia , Animais , Bacillus thuringiensis/genética , Proteínas de Bactérias/metabolismo , Borboletas/efeitos dos fármacos , Borboletas/metabolismo , Endotoxinas/metabolismo , Proteínas Hemolisinas/genética , Larva/efeitos dos fármacos , Plantas Geneticamente Modificadas/metabolismo , Pólen , Espanha , Zea mays/genética
14.
GM Crops Food ; 12(1): 1-17, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-32762312

RESUMO

A biophysical survey was conducted in 15 cotton-growing districts of Pakistan. Four hundred cotton growers were approached and inquired about the production technology of Bt cotton. Further, 25 strip tests using combo strips (Cry1Ac, Cry2Ab, Vip3Aa and Cp4, EPSPS gene) were performed at each farmer's field. Out of 10,000 total-tested samples, farmers claimed 9682 samples as Bt and 318 samples as non-Bt. After performing a strip test, 1009 and 87 samples were found false negative and false positive, respectively. Only 53 samples were found positive for Cry2Ab, 214 for EPSPS and none for Vip3Aa gene. Quantification of Cry endotoxin and bioassay studies were performed by taking leaves from upper, middle, and lower canopies, and fruiting parts at approximately 80 days after sowing from 89 varieties. Expression was highly variable among different canopies and fruiting parts. Moreover, Cry endotoxin expression and insect mortality varied significantly among varieties from 0.26 µg g-1 to 3.54 µg g-1 with mortality ranging from 28 to 97%, respectively. Highest Cry1Ac expression (3.54 µg g-1) and insect mortality (97%) were observed for variety FH-142 from DG Khan. Cry endotoxin expression varied significantly across various plant parts, i.e., IUB-13 variety from upper canopy documented 0.34 µg g-1 expression with 37% insect mortality in Layyah to 3.42 µg g-1 expression and 96% insect mortality from DG Khan. Lethal dose, LD95 (2.20 µg g-1) of Cry1Ac endotoxin was optimized for effective control of H. armigera. Our results provided evidence of practical resistance in H. armigera and way forward.


Assuntos
Proteínas Hemolisinas/genética , Mariposas , Animais , Proteínas de Bactérias/genética , Endotoxinas , Gossypium , Resistência a Inseticidas , Larva , Paquistão , Plantas Geneticamente Modificadas
15.
Food Microbiol ; 93: 103604, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32912579

RESUMO

This study addresses the biodiversity of Bacillus cereus group population present along the value chain of milk for consumption. The B. cereus population did not grow and remained mainly unaltered during storage of milk at 4 °C while storage at a suboptimal temperature at 8 °C (representative of a broken cold chain) caused a major shift in its composition. Mesophilic strains dominated the B. cereus population in raw milk and after storage at 4 °C, while psycrotrophic strains dominated after storage at 8 °C. All psycrotrophic and mesophilic isolates (n = 368) demonstrated high spoilage potentials of the milk components. Fifteen out of 20 mesophilic isolates but only two out of 40 psychrotrophic isolates, exhibited vero cell toxicity. No genes encoding the emetic toxin cereulide were detected in the genomes of 100 milk isolates while 14 of them harbored the enterotoxin genes cytK1/cytK2. Both psycrotrophic and mesophilic isolates carried the enterotoxin genes nheA and hblA. Together, the results provide insight into the composition and properties, of the B. cereus population present in milk along the value chain and during storage at optimal refrigerated temperature and at suboptimal temperature. This knowledge is useful in the dairy industry's work to assure high quality products and for risk assessment.


Assuntos
Bacillus cereus/classificação , Bacillus cereus/genética , Bacillus cereus/isolamento & purificação , Microbiologia de Alimentos , Leite/microbiologia , Animais , Proteínas de Bactérias/genética , Toxinas Bacterianas/genética , Biodiversidade , DNA Bacteriano/genética , Depsipeptídeos , Enterotoxinas/genética , Fermentação , Contaminação de Alimentos/análise , Proteínas Hemolisinas/genética , Filogenia , Temperatura
16.
Ecotoxicol Environ Saf ; 207: 111214, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-32890949

RESUMO

The potential risk of Bt (Bacillus thuringiensis) crops on non-target organisms (NTOs) has drawn a lot of public concerns. Despite a series of risk assessments of Bt crops on NTOs has been conducted, a quantitative approach which could support a precise judgment of their safety is required. In the present work, hazard quotient (HQ) was applied in the safety evaluation of three Bt rice events (Cry1Ab, Cry1C and Cry2Aa rice) on NTOs. Eight NTOs in different functional guilds associated with Bt rice were selected to conduct the tests. The results showed that the HQs of three Bt rice events for eight NTOs were all below the trigger value 1, while the HQ of Cry1Ab rice for one target pest Chilo suppressalis was three times higher than 1. Our results assured the reliability of the HQ and indicated that the three Bt rice events would pose no risks to the eight NTOs. Further testing of three Bt proteins on biological parameters of one NTO Nasonia virtipennis under no observed adverse effect concentration (NOAEC) confirmed the robustness of HQ assessment. We recommend that the HQ could be applied in tier-1 risk assessments of Bt crops on NTOs as a reference data standard, which would provide more clear and credible safety information of transgenic crops for the public and policy makers.


Assuntos
/toxicidade , Endotoxinas/toxicidade , Proteínas Hemolisinas/toxicidade , Oryza/genética , Plantas Geneticamente Modificadas , Animais , Bacillus thuringiensis/genética , Proteínas de Bactérias/metabolismo , Produtos Agrícolas/metabolismo , Endotoxinas/metabolismo , Proteínas Hemolisinas/genética , Mariposas , Oryza/metabolismo , Controle Biológico de Vetores/métodos , Reprodutibilidade dos Testes
17.
Pest Manag Sci ; 77(1): 335-342, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32729162

RESUMO

BACKGROUND: The widespread adoption of genetically modified crops, including Bacillius thuringensis (Bt) crops that target chewing insects, has transformed agricultural pest management. This increased use of Bt has raised concerns about the onset of resistance amongst target pests. Recent studies have shown that for some caterpillars, nutritional foraging (e.g. the ratio of proteins and carbohydrates consumed) can affect the insect susceptibility to the Bt toxin Cry1Ac. However, studies on both nutritional foraging and Bt susceptibility tend to rely on laboratory colonies without specifically addressing physiological differences that may occur between populations of the same species. Here, we used choice assays, no choice assays and dose response assays to address two overarching questions: Do populations of Spodoptera frugiperda (J.E. Smith) vary in their protein-carbohydrate foraging behavior? and Does protein-carbohydrate intake impact S. frugiperda's susceptibility to the Bt toxin Cry1F? RESULTS: All three of our S. frugiperda populations actively regulated their protein-carbohydrate intake, but we observed significant differences between populations with respect to their self-selected protein-carbohydrate intake. We also found that feeding at the protein-carbohydrate intake target slightly increased Cry1F susceptibility for one S. frugiperda population, but had no effect on the other two populations. CONCLUSIONS: Our findings indicate that inherent differences exist in the nutritional physiology of three S. frugiperda populations, possibly related to the time spent in culture. This suggests that population-level differences are an important consideration when drawing parallels between field-collected and laboratory-reared insects.


Assuntos
Bacillus thuringiensis , Proteínas Hemolisinas , Animais , Bacillus thuringiensis/genética , Proteínas de Bactérias/genética , Carboidratos , Produtos Agrícolas , Endotoxinas , Proteínas Hemolisinas/genética , Resistência a Inseticidas , Plantas Geneticamente Modificadas/genética , Spodoptera , Zea mays/genética
18.
PLoS One ; 15(9): e0238523, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32911522

RESUMO

Brazil and South Africa, countries with economies in transition, are characterized by a dual agrarian structure co-occurring, sometimes, alongside in the same region. Large-scale commercial farming produces crops for export to global markets on the one hand, and small-scale farming, on the other hand, provides for subsistence and local markets. In both systems, maize (Zea mays) is a key crop for these two countries. For the commercial system, maize is a commodity crop while for the small-scale system it is the prime staple crop. In commercial systems, farmers predominantly grow genetically modified (GM) hybrid maize. In small-scale systems, farmers rely on open pollinated varieties (OPVs) and/or landraces and are largely dependent on seed saving systems. The aim of this study was to understand the relationship between transgene expression rates, the resulting concentrations of the transgene product (Bt protein) and its bioactivity in insect pests following transgene flow from GM hybrid maize into non-genetically modified, non-GM near-isogenic maize hybrid (ISO) and OPVs. We modeled segregation patterns and measured cry1Ab transgene expression (mRNA quantification), Cry1Ab protein concentration and pest survival. Two groups of F1, F2 crosses and backcrosses with GM, ISO and OPV maize varieties from Brazil and South Africa were used. Bioassays with the larvae of two lepidopteran maize pest species, Helicoverpa armigera and Spodoptera littoralis, were carried out. Overall, the cry1Ab transgene outcrossed effectively into the genetic backgrounds tested. The cry1Ab transgene was stably expressed in both ISO and OPV genetic backgrounds. Transgene introgression led to consistent, though highly variable, concentrations of Cry1Ab toxins that were similar to those observed in GM parental maize. Most crosses, but not all, suggested the expected Mendelian segregation pattern. Transgene expression rates were significantly higher than expected from purely Mendelian segregation in the South African crosses. In South African materials, ISO and OPV crosses produced significantly lower Cry1Ab concentrations compared to the GM parental maize. The Cry1Ab toxins from crosses were bioactive and induced mortality rates of ≥92.19% in H. armigera and ≥40.63% in S. littoralis after a period of only 4 days. However, no correlations were observed between the quantitation of mRNA for cry1Ab and the corresponding Cry1Ab protein concentrations, nor between the Cry1Ab concentrations and insect mortality rates across different genetic backgrounds. We therefore suggest that while transcription of the cry1Ab transgene reliably determines the presence of Cry1Ab protein, mRNA levels do not reflect, by themselves, the end Cry1Ab protein concentrations found in the plant. Because predictably high Cry1Ab concentrations are a key prerequisite for effective insect resistance management (IRM) programs, this observation raises questions about the effectiveness of such programs in scenarios with complex crop genetic backgrounds. On the other hand, confirmed bioactivity in all crosses should be expected to impact small farmer's selection behavior, unknowingly favoring the insecticidal trait. This may lead to a fixation of the trait in the wider population, and may influence the genetic diversity of varieties maintained by small-scale farmers.


Assuntos
Proteínas de Bactérias/genética , Endotoxinas/genética , Proteínas Hemolisinas/genética , Controle Biológico de Vetores , Plantas Geneticamente Modificadas/genética , Zea mays/genética , Animais , Produtos Agrícolas/genética , Cruzamentos Genéticos , Resistência à Doença , Doenças das Plantas/genética , Doenças das Plantas/parasitologia , Plantas Geneticamente Modificadas/parasitologia , Spodoptera/fisiologia , Transgenes , Zea mays/parasitologia
19.
Wei Sheng Yan Jiu ; 49(4): 569-573, 2020 Jul.
Artigo em Chinês | MEDLINE | ID: mdl-32928347

RESUMO

OBJECTIVE: To evaluate the effects of genetically modified maize with Cry1Ab and epsps genes on immune function in F3 rats. METHODS: A total of 180 weaning SD rats for F0 generation were randomly divided into three groups, which were treated with AIN-93 G feed control diet, parental maize diet and genetically modified maize diet respectively. After three generations of breeding, antibody producing cells determination, concanavalin A(ConA)-induced lymphocyte transformation test, natural killer(NK)cells activities assay, whole blood lymphocyte subtype detection, delayed type hypersensitivity test and immunity organ index were performed. RESULTS: There were no significant differences between parental maize diet and genetically modified maize diet in terms of the number of antibody-producing cells, ConA-induced spleen lymphocyte proliferation, NK cell activity, whole blood lymphocyte subsets, delayed type hypersensitivity and thymus index(P>0. 05). CONCLUSION: Under the conditions of this experiment, no significant effects were found on immune function of F3 SD rats through the three generation development study of genetically modified maize with CrylAb and epsps genes.


Assuntos
Alimentos Geneticamente Modificados , Zea mays/genética , Animais , Proteínas de Bactérias/genética , Endotoxinas , Proteínas Hemolisinas/genética , Plantas Geneticamente Modificadas , Ratos , Ratos Sprague-Dawley
20.
Proc Natl Acad Sci U S A ; 117(38): 23774-23781, 2020 09 22.
Artigo em Inglês | MEDLINE | ID: mdl-32878997

RESUMO

Intracellular pathogens are responsible for an enormous amount of worldwide morbidity and mortality, and each has evolved specialized strategies to establish and maintain their replicative niche. Listeria monocytogenes is a facultative intracellular pathogen that secretes a pore-forming cytolysin called listeriolysin O (LLO), which disrupts the phagosomal membrane and, thereby, allows the bacteria access to their replicative niche in the cytosol. Nonsynonymous and synonymous mutations in a PEST-like domain near the LLO N terminus cause enhanced LLO translation during intracellular growth, leading to host cell death and loss of virulence. Here, we explore the mechanism of translational control and show that there is extensive codon restriction within the PEST-encoding region of the LLO messenger RNA (mRNA) (hly). This region has considerable complementarity with the 5' UTR and is predicted to form an extensive secondary structure that overlaps the ribosome binding site. Analysis of both 5' UTR and synonymous mutations in the PEST-like domain that are predicted to disrupt the secondary structure resulted in up to a 10,000-fold drop in virulence during mouse infection, while compensatory double mutants restored virulence to WT levels. We showed by dynamic protein radiolabeling that LLO synthesis was growth phase-dependent. These data provide a mechanism to explain how the bacteria regulate translation of LLO to promote translation during starvation in a phagosome while repressing it during growth in the cytosol. These studies also provide a molecular explanation for codon bias at the 5' end of this essential determinant of pathogenesis.


Assuntos
Toxinas Bacterianas , Proteínas de Choque Térmico , Proteínas Hemolisinas , Listeria monocytogenes , RNA Bacteriano/química , RNA Mensageiro/química , Regiões 5' não Traduzidas/genética , Animais , Toxinas Bacterianas/química , Toxinas Bacterianas/genética , Toxinas Bacterianas/metabolismo , Replicação do DNA/genética , Proteínas de Choque Térmico/química , Proteínas de Choque Térmico/genética , Proteínas de Choque Térmico/metabolismo , Proteínas Hemolisinas/química , Proteínas Hemolisinas/genética , Proteínas Hemolisinas/metabolismo , Listeria monocytogenes/genética , Listeria monocytogenes/patogenicidade , Listeriose , Camundongos , Conformação de Ácido Nucleico , RNA Bacteriano/genética , RNA Mensageiro/genética
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