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1.
Toxicity and Mode of Action of Bacillus thuringiensis Cry Proteins in the Mediterranean Corn Borer, Sesamia nonagrioides (Lefebvre) 总被引:1,自引:0,他引:1
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Joel Gonzlez-Cabrera Gema P. Farins Silvia Caccia Mercedes Díaz-Mendoza Pedro Castaera Maria Giovanna Leonardi Barbara Giordana Juan Ferr 《Applied microbiology》2006,72(4):2594-2600
Sesamia nonagrioides is one of the most damaging pests of corn in Spain and other Mediterranean countries. Bt corn expressing the Bacillus thuringiensis Cry1Ab toxin is being grown on about 58,000 ha in Spain. Here we studied the mode of action of this Cry protein on S. nonagrioides (binding to specific receptors, stability of binding, and pore formation) and the modes of action of other Cry proteins that were found to be active in this work (Cry1Ac, Cry1Ca, and Cry1Fa). Binding assays were performed with 125I- or biotin-labeled toxins and larval brush border membrane vesicles (BBMV). Competition experiments indicated that these toxins bind specifically and that Cry1Aa, Cry1Ab, and Cry1Ac share a binding site. Cry1Ca and Cry1Fa bind to different sites. In addition, Cry1Fa binds to Cry1A's binding site with very low affinity and vice versa. Binding of Cry1Ab and Cry1Ac was found to be stable over time, which indicates that the observed binding is irreversible. The pore-forming activity of Cry proteins on BBMV was determined using the voltage-sensitive fluorescent dye DiSC3(5). Membrane permeability increased in the presence of the active toxins Cry1Ab and Cry1Fa but not in the presence of the nonactive toxin Cry1Da. In terms of resistance management, based on our results and the fact that Cry1Ca is not toxic to Ostrinia nubilalis, we recommend pyramiding of Cry1Ab with Cry1Fa in the same Bt corn plant for better long-term control of corn borers. 相似文献
2.
Can Zhao Juan Luis Jurat-Fuentes Heba M. Abdelgaffar Hongyu Pan Fuping Song Jie Zhang 《Applied and environmental microbiology》2015,81(11):3699-3705
Pyramiding of diverse cry toxin genes from Bacillus thuringiensis with different modes of action is a desirable strategy to delay the evolution of resistance in the European corn borer (Ostrinia nubilalis). Considering the dependency of susceptibility to Cry toxins on toxin binding to receptors in the midgut of target pests, a diverse mode of action is commonly defined as recognition of unique binding sites in the target insect. In this study, we present a novel cry1Ie toxin gene (cry1Ie2) as a candidate for pyramiding with Cry1Ab or Cry1Fa in corn to control Ostrinia species larvae. The new toxin gene encodes an 81-kDa protein that is processed to a protease-resistant core form of approximately 55 kDa by trypsin digestion. The purified protoxin displayed high toxicity to Ostrinia furnacalis and O. nubilalis larvae but low to no activity against Spodoptera or heliothine species or the coleopteran Tenebrio molitor. Results of binding assays with 125I-labeled Cry1Ab toxin and brush border membrane vesicles from O. nubilalis larvae demonstrated that Cry1Ie2 does not recognize the Cry1Ab binding sites in that insect. Reciprocal competition binding assays with biotin-labeled Cry1Ie2 confirmed the lack of shared sites with Cry1Ab or Cry1Fa in O. nubilalis brush border membrane vesicles. These data support Cry1Ie2 as a good candidate for pyramiding with Cry1Ab or Cry1Fa in corn to increase the control of O. nubilalis and reduce the risk of resistance evolution. 相似文献
3.
Importance of Cry1 δ-Endotoxin Domain II Loops for Binding Specificity in Heliothis virescens (L.)
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We constructed a model for Bacillus thuringiensis Cry1 toxin binding to midgut membrane vesicles from Heliothis virescens. Brush border membrane vesicle binding assays were performed with five Cry1 toxins that share homologies in domain II loops. Cry1Ab, Cry1Ac, Cry1Ja, and Cry1Fa competed with 125I-Cry1Aa, evidence that each toxin binds to the Cry1Aa binding site in H. virescens. Cry1Ac competed with high affinity (competition constant [Kcom] = 1.1 nM) for 125I-Cry1Ab binding sites. Cry1Aa, Cry1Fa, and Cry1Ja also competed for 125I-Cry1Ab binding sites, though the Kcom values ranged from 179 to 304 nM. Cry1Ab competed for 125I-Cry1Ac binding sites (Kcom = 73.6 nM) with higher affinity than Cry1Aa, Cry1Fa, or Cry1Ja. Neither Cry1Ea nor Cry2Aa competed with any of the 125I-Cry1A toxins. Ligand blots prepared from membrane vesicles were probed with Cry1 toxins to expand the model of Cry1 receptors in H. virescens. Three Cry1A toxins, Cry1Fa, and Cry1Ja recognized 170- and 110-kDa proteins that are probably aminopeptidases. Cry1Ab and Cry1Ac, and to some extent Cry1Fa, also recognized a 130-kDa molecule. Our vesicle binding and ligand blotting results support a determinant role for domain II loops in Cry toxin specificity for H. virescens. The shared binding properties for these Cry1 toxins correlate with observed cross-resistance in H. virescens. 相似文献
4.
Analyses of Cry1Ab Binding in Resistant and Susceptible Strains of the European Corn Borer, Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae)
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Herbert A. A. Siqueira Joel Gonzlez-Cabrera Juan Ferr Ronald Flannagan Blair D. Siegfried 《Applied microbiology》2006,72(8):5318-5324
Cry1Ab toxin binding analysis was performed to determine whether resistance in laboratory-selected Ostrinia nubilalis strains is associated with target site alteration. Brush border membrane vesicles were prepared using dissected midguts from late instars of susceptible and resistant strains (Europe-R and RSTT) of O. nubilalis. Immunoblot analysis indicated that three different proteins bound to Cry1Ab toxin and were recognized by an anticadherin serum. In a comparison of resistant and susceptible strains, reduced Cry1Ab binding was apparent for all three bands corresponding to cadherin-like proteins in the Europe-R strain, while reduced binding was apparent in only one band for the RSTT strain. Real-time analysis of Cry1Ab binding to gut receptors using surface plasmon resonance suggested slight differences in affinity in both resistant strains. Additional binding analysis was conducted using 125I-labeled Cry1Ab, Cry1Ac, and Cry1Aa. Slight differences were again observed between the resistant and susceptible strains for Cry1Ab binding. However, when binding of 125I-labeled Cry1Aa was tested, a 10-fold reduction in the concentration of binding sites was observed in the Europe-R strain. Expression of the O. nubilalis cadherin gene was similar in both the resistant and susceptible strains and did not account for differences in binding. In combination, the results of the present work suggest that differences in susceptibility to Cry1A toxins in the Europe-R strain of O. nubilalis are associated with altered receptor binding, although the precise nature of this mechanism is still uncertain. 相似文献
5.
Kirouac M Vachon V Rivest S Schwartz JL Laprade R 《The Journal of membrane biology》2003,196(1):51-59
A potential-sensitive fluorescent probe, 3,3-dipropylthiadicarbocyanine iodide, was used to analyze, at pH 7.5 and 10.5, the effects of Bacillus thuringiensis toxins on the membrane potential generated by the efflux of K+ ions from brush border membrane vesicles purified from the midgut of the tobacco hornworm, Manduca sexta. Fluorescence levels were strongly influenced by the pH and ionic strength of the media. Therefore, characterization of the effects of the toxins was conducted at constant pH and ionic strength. Under these conditions, the toxins had little effect on the fluorescence levels measured in the presence or absence of ionic gradients, indicating that the ionic selectivity of their pores is similar to that of the intact membrane. Valinomycin greatly increased the potential generated by the diffusion of K+ ions although membrane permeability to the other ions used to maintain the ionic strength constant also influenced fluorescence levels. In the presence of valinomycin, active toxins (Cry1Aa, Cry1Ab, Cry1Ac, Cry1C and Cry1E) efficiently depolarized the membrane at pH 7.5 and 10.5. 相似文献
6.
Summary The voltage- and time-dependent K+ current,I
K
+
out
, elicited by depolarization of corn protoplasts, was inhibited by the addition of calcium channel antagonists (nitrendipine, nifedipine, verapamil, methoxyverapamil, bepridil, but not La3+) to the extracellular medium. These results suggested that the influx of external Ca2+ was necessary for K+ current activation. The IC50, concentration of inhibitor that caused 50% reduction of the current, for nitrendipine was 1 m at a test potential of +60 mV following a 20-min incubation period.In order to test whether intracellular Ca2+ actuated the K+ current, we altered either the Ca2+ buffering capacity or the free Ca2+ concentration of the intracellular medium (pipette filling solution). By these means,I
K
+
out
could be varied over a 10-fold range. Increasing the free Ca2+ concentration from 40 to 400nm also shifted the activation of the K+ current toward more negative potentials. Maintaining cytoplasmic Ca2+ at 500nm with 40nm EGTA resulted in a more rapid activation of the K+ current. Thus the normal rate of activation of this current may reflect changes in cytoplasmic Ca2+ on depolarization. Increasing intracellular Ca2+ to 500nm or 1 m also led to inactivation of the K+ current within a few minutes. It is concluded thatI
K
+
out
is regulated by cytosolic Ca2+, which is in turn controlled by Ca2+ influx through dihydropyridine-, and phenylalkylamine-sensitive channels. 相似文献
7.
Sek Yee Tan Bonifacio F. Cayabyab Edwin P. Alcantara Fangneng Huang Kanglai He Kenneth W. Nickerson Blair D. Siegfried 《Journal of invertebrate pathology》2013
The European (Ostrinia nubilalis Hübner) and Asian corn borers (Ostrinia furnacalis Guenée) are closely related and display similar sensitivity to Cry1 toxins. In this study, we compared the binding patterns of Cry1Ab and Cry1F toxins between both Ostrinia spp., as well as the expression of putative cadherin- and aminopeptidase-N (APN)-like protein receptors. Additionally, cDNA sequences of these putative toxin receptors from both Ostrinia species were compared. Ligand blots for both species indicated a similar binding pattern for Cry1Ab with the strongest immunoreactive band at 260 kDa in both species. In addition, similar expression of the putative cadherin- and APN-like protein receptors were observed at 260 and 135 kDa, respectively. A high degree of similarity (98% amino acid sequence identity) of cDNA sequences for both putative receptor sequences was observed. The Cry1F ligand blot revealed that O. furnacalis and O. nubilalis BBMV exhibited slightly different binding patterns, with strong binding to putative proteins at 150 and 140 kDa, respectively. Both proteins appeared to also bind Cry1Ab, although the signal intensity was much reduced with Cry1Ab. O. furnacalis showed an additional but weaker band at 210 kDa relative to the 150 kDa band. Diatraea saccharalis (Fabricius), which was used as an outgroup species, exhibited different binding patterns than either Ostrinia species, with both Cry1Ab and Cry1F toxins binding to a 210 kDa protein. These results support the previous experiments indicating that O. nubilalis and O. furnacalis share similar patterns of susceptibility to Cry toxins. 相似文献
8.
Use of Bacillus thuringiensis Toxins for Control of the Cotton Pest Earias insulana (Boisd.) (Lepidoptera: Noctuidae)
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María A. Ibargutxi Anna Estela Juan Ferr Primitivo Caballero 《Applied microbiology》2006,72(1):437-442
Thirteen of the most common lepidopteran-specific Cry proteins of Bacillus thuringiensis have been tested for their efficacy against newly hatched larvae of two populations of the spiny bollworm, Earias insulana. At a concentration of 100 μg of toxin per milliliter of artificial diet, six Cry toxins (Cry1Ca, Cry1Ea, Cry1Fa, Cry1Ja, Cry2Aa, and Cry2Ab) were not toxic at all. Cry1Aa, Cry1Ja, and Cry2Aa did not cause mortality but caused significant inhibition of growth. The other Cry toxins (Cry1Ab, Cry1Ac, Cry1Ba, Cry1Da, Cry1Ia, and Cry9Ca) were toxic to E. insulana larvae. The 50% lethal concentration values of these toxins ranged from 0.39 to 21.13 μg/ml (for Cry9Ca and Cry1Ia, respectively) for an E. insulana laboratory colony originating from Egypt and from 0.20 to 4.25 μg/ml (for Cry9Ca and Cry1Da, respectively) for a laboratory colony originating from Spain. The relative potencies of the toxins in the population from Egypt were highest for Cry9Ca and Cry1Ab, and they were both significantly more toxic than Cry1Ac and Cry1Ba, followed by Cry1Da and finally Cry1Ia. In the population from Spain, Cry9Ca was the most toxic, followed in decreasing order by Cry1Ac and Cry1Ba, and the least toxic was Cry1Da. Binding experiments were performed to test whether the toxic Cry proteins shared binding sites in this insect. 125I-labeled Cry1Ac and Cry1Ab and biotinylated Cry1Ba, Cry1Ia, and Cry9Ca showed specific binding to the brush border membrane vesicles from E. insulana. Competition binding experiments among these toxins showed that only Cry1Ab and Cry1Ac competed for the same binding sites, indicating a high possibility that this insect may develop cross-resistance to Cry1Ab upon exposure to Cry1Ac transgenic cotton but not to the other toxins tested. 相似文献
9.
Ishikawa H Hoshino Y Motoki Y Kawahara T Kitajima M Kitami M Watanabe A Bravo A Soberon M Honda A Yaoi K Sato R 《Molecular biotechnology》2007,36(2):90-101
Theoretically, the activity of AB-type toxin molecules such as the insecticidal toxin (Cry toxin) from B. thuringiensis, which have one active site and two binding site, is improved in parallel with the binding affinity to its receptor. In this
experiment, we tried to devise a method for the directed evolution of Cry toxins to increase the binding affinity to the insect
receptor. Using a commercial T7 phage-display system, we expressed Cry1Aa toxin on the phage surface as fusions with the capsid
protein 10B. These recombinant phages bound to a cadherin-like protein that is one of the Cry1Aa toxin receptors in the model
target insect Bombyx mori. The apparent affinity of Cry1Aa-expressing phage for the receptor was higher than that of Cry1Ab-expressing phage. Phages
expressing Cry1Aa were isolated from a mixed suspension of phages expressing Cry1Ab and concentrated by up to 130,000-fold.
Finally, random mutations were made in amino acid residues 369–375 in domain 2 of Cry1Aa toxin, the mutant toxins were expressed
on phages, and the resulting phage library was screened with cadherin-like protein-coated beads. As a result, phages expressing
abnormal or low-affinity mutant toxins were excluded, and phages with high-affinity mutant toxins were selected. These results
indicate that a method combining T7 phage display with selection using cadherin-like protein-coated magnetic beads can be
used to increase the activity of easily obtained, low-activity Cry toxins from bacteria. 相似文献
10.
Summary Delta endotoxin, a 68 kilodalton protein isolated fromBacillus thuringiensis spp.Kurstaki, is a potent entomocidal agent that alters a K+ current across midgut tissue of many phytophagous insects. This toxin completely inhibited the vanadate-sensitive86Rb+ uptake and mimicked the vanadate-induced decrease in cytosolic pH in a cell line (CHE) originating fromManduca sexta embryonic tissue. The toxin also inhibited a K+-sensitive-ATPase in the plasma membranes isolated from these cells. Using the K+-sensitive-ATPase substratp-nitrophenyl phosphate, delta endotoxin was found to have aK
i
of 0.4 m. These data suggest that the toxin inhibits a K+-ATPase responsible for86Pb+ uptake in the CHE cells. The relationship between the toxin inhibition of K+-ATPase and toxin-altered K+ current is discussed. 相似文献
11.
Avilla C Vargas-Osuna E González-Cabrera J Ferré J González-Zamora JE 《Journal of invertebrate pathology》2005,90(1):51-54
Toxicity and larval growth inhibition of 11 insecticidal proteins of Bacillus thuringiensis were evaluated against neonate larvae of Helicoverpa armigera, a major pest of important crops in Spain and other countries, by a whole-diet contamination method. The most active toxins were Cry1Ac4 and Cry2Aa1, with LC50 values of 3.5 and 6.3 microg/ml, respectively. At the concentrations tested, Cry1Ac4, Cry2Aa1, Cry9Ca, Cry1Fa1, Cry1Ab3, Cry2Ab2, Cry1Da, and Cry1Ja1, produced a significant growth inhibition, whereas Cry1Aa3, Cry1Ca2, and Cry1Ea had no effect. 相似文献
12.
Eliseu J.G. Pereira Meibao Zhuang Blair D. Siegfried 《Journal of invertebrate pathology》2010,103(1):1-7
The biochemical mechanism of resistance to the Bacillus thuringiensis Cry1F toxin was studied in a laboratory-selected strain of Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae) showing more than 3000-fold resistance to Cry1F and limited cross resistance to other Cry toxins. Analyses of Cry1F binding to brush border membrane vesicles of midgut epithelia from susceptible and resistant larvae using ligand immunoblotting and Surface Plasmon Resonance (SPR) suggested that reduced binding of Cry1F to insect receptors was not associated with resistance. Additionally, no differences in activity of luminal gut proteases or altered proteolytic processing of the toxin were observed in the resistant strain. Considering these results along with previous evidence of relatively narrow spectrum of cross resistance and monogenic inheritance, the resistance mechanism in this Cry1F selected strain of O. nubilalis appears to be specific and may be distinct from previously identified resistance mechanisms reported in other Lepidoptera. 相似文献
13.
Muñoz-Garay C Sánchez J Darszon A de Maagd RA Bakker P Soberón M Bravo A 《The Journal of membrane biology》2006,212(1):61-68
The pore-formation activity of monomeric and oligomeric forms of different Cry1 toxins (from Cry1A to Cry1G) was analyzed
by monitoring ionic permeability across Manduca sexta brush border membrane vesicles. The membrane vesicles were isolated from microvilli structures, showing a high enrichment
of apical membrane markers and low intrinsic K+ permeability. A fluorometric assay performed with 3,3′-dipropylthiodicarbocyanine fluorescent probe, sensitive to changes
in membrane potential, was used. Previously, it was suggested that fluorescence determinations with this dye could be strongly
influenced by the pH, osmolarity and ionic strength of the medium. Therefore, we evaluated these parameters in control experiments
using the K+-selective ionophore valinomycin. We show here that under specific ionic conditions changes in fluorescence can be correlated
with ionic permeability without effects on osmolarity or ionic strength of the medium. It is extremely important to attenuate
the background response due to surface membrane potential and the participation of the endogenous permeability of the membrane
vesicles. Under these conditions, we analyzed the pore-formation activity induced by monomeric and oligomeric structures of
different Cry1 toxins. The Cry1 toxin samples containing oligomeric structures correlated with high pore activity, in contrast
to monomeric samples that showed marginal pore-formation activity, supporting the hypothesis that oligomer formation is a
necessary step in the mechanism of action of Cry toxins. 相似文献
14.
González-Cabrera J Farinós GP Caccia S Díaz-Mendoza M Castañera P Leonardi MG Giordana B Ferré J 《Applied and environmental microbiology》2006,72(4):2594-2600
Sesamia nonagrioides is one of the most damaging pests of corn in Spain and other Mediterranean countries. Bt corn expressing the Bacillus thuringiensis Cry1Ab toxin is being grown on about 58,000 ha in Spain. Here we studied the mode of action of this Cry protein on S. nonagrioides (binding to specific receptors, stability of binding, and pore formation) and the modes of action of other Cry proteins that were found to be active in this work (Cry1Ac, Cry1Ca, and Cry1Fa). Binding assays were performed with (125)I- or biotin-labeled toxins and larval brush border membrane vesicles (BBMV). Competition experiments indicated that these toxins bind specifically and that Cry1Aa, Cry1Ab, and Cry1Ac share a binding site. Cry1Ca and Cry1Fa bind to different sites. In addition, Cry1Fa binds to Cry1A's binding site with very low affinity and vice versa. Binding of Cry1Ab and Cry1Ac was found to be stable over time, which indicates that the observed binding is irreversible. The pore-forming activity of Cry proteins on BBMV was determined using the voltage-sensitive fluorescent dye DiSC(3)(5). Membrane permeability increased in the presence of the active toxins Cry1Ab and Cry1Fa but not in the presence of the nonactive toxin Cry1Da. In terms of resistance management, based on our results and the fact that Cry1Ca is not toxic to Ostrinia nubilalis, we recommend pyramiding of Cry1Ab with Cry1Fa in the same Bt corn plant for better long-term control of corn borers. 相似文献
15.
Specific Binding of Bacillus thuringiensis Cry2A Insecticidal Proteins to a Common Site in the Midgut of Helicoverpa Species 总被引:2,自引:0,他引:2
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Carmen Sara Hernndez-Rodríguez Adri Van Vliet Nadine Bautsoens Jeroen Van Rie Juan Ferr 《Applied microbiology》2008,74(24):7654-7659
For a long time, it has been assumed that the mode of action of Cry2A toxins was unique and different from that of other three-domain Cry toxins due to their apparent nonspecific and unsaturable binding to an unlimited number of receptors. However, based on the homology of the tertiary structure among three-domain Cry toxins, similar modes of action for all of them are expected. To confirm this hypothesis, binding assays were carried out with 125I-labeled Cry2Ab. Saturation assays showed that Cry2Ab binds in a specific and saturable manner to brush border membrane vesicles (BBMVs) of Helicoverpa armigera. Homologous-competition assays with 125I-Cry2Ab demonstrated that this toxin binds with high affinity to binding sites in H. armigera and Helicoverpa zea midgut. Heterologous-competition assays showed a common binding site for three toxins belonging to the Cry2A family (Cry2Aa, Cry2Ab, and Cry2Ae), which is not shared by Cry1Ac. Estimation of Kd (dissociation constant) values revealed that Cry2Ab had around 35-fold less affinity than Cry1Ac for BBMV binding sites in both insect species. Only minor differences were found regarding Rt (concentration of binding sites) values. This study questions previous interpretations from other authors performing binding assays with Cry2A toxins and establishes the basis for the mode of action of Cry2A toxins. 相似文献
16.
The efficacy and mechanism of -dendrotoxin (DTX) block of K+ channel currents in Vicia stomatal guard cells was examined. Currents carried by inward- and outward-rectifying K+ channels were determined under voltage clamp in intact guard cells, and block was characterized as a function of DTX and external K+ (K+) concentrations. Added to the bath, 0.1-30 nM DTX blocked the inward-rectifying K+ current (IK,in), but was ineffective in blocking current through the outward-rectifying K+ channels (IK,out) even at concentrations of 30 nM. DTX block was independent of clamp voltage and had no significant effect on the voltage-dependent kinetics for IK,in, neither altering its activation at voltages negative of –120 mV nor its deactivation at more positive voltages. No evidence was found for a use dependence to DTX action. Block of IK,in followed a simple titration function with an apparent K1/2 for block of 2.2 nM in 3 mm K
o
+
. However, DTX block was dependent on the external K+ concentration. Raising K+ from 3 to 30 mm slowed block and resulted in a 60–70% reduction in its efficacy (apparent K
i
= 10 mm in 10 nm DTX). The effect of K+ in protecting I
K,in
was competitive with DTX and specific for permeant cations. A joint analysis of IK,in block with DTX and K+ concentration was consistent with a single class of binding sites with a K
d
for DTX of 240 pm. A K
d
of 410 m for extracellular K+ was also indicated. These results complement previous studies implicating a binding site requiring extracellular K+ (K1/2 1 mm) for IK,in activation; they parallel features of K+ channel block by DTX and related peptide toxins in many animal cells, demonstrating the sensitivity of plant plasma membrane K+ channels to nanomolar toxin concentrations under physiological conditions; the data also highlight one main difference: in the guard cells, DTX action appears specific to the K+ inward rectifier.We thank J.O. Dolly (Imperial, London) and S.M. Jarvis (University of Kent, Canterbury) for several helpful discussions. This work was supported by SERC grant GR/H07696 and was aided by equipment grants from the Gatsby Foundation, the Royal Society and the University of London Central Research Fund. G.O. was supported by an Ausbildungsstipendium (OB 85/1-1) from the Deutsche Forschungsgemeinschaft. F.A. holds a Sainsbury Studentship. 相似文献
17.
Bioassays and binding tests between Cry toxins (CrylAa, CrylAb, CrylAc, and Cry2Ab) and brush-border membrane vesicles (BBMVs) from larvae of a Bacillus thurningiensis (Bt)-susceptible (96S) and two CrylAc-resistant strains (BtR and LFR10) were conducted for investigating cross-resistance of CrylAc-resistant strains to Cry2Ab in Helicoverpa armigera (Hiibner) (Lepidoptera: Noctuidae). The resistance ratio (RR) values of the BtR and LFR10 strains to CrylAc and Cry2Ab were 2,971- and 1.1-fold and 253- and 1.0-fold, respectively, indicating that there was no cross-resistance to Cry2Ab. The binding experiments between Cry toxins and BBMVs from BtR, LFR10, and 96S larvae showed that all of the toxins could bind with these BBMVs, but the Cry2Ab could not displace 125I labeled CrylAc and CrylAb. The same results were observed in reciprocal binding tests, demonstrating that CrylA and Cry2Ab had different binding sites in H. armigera and providing a potential mechanism for the lack of cross-resistance between CrylA and Cry2Ab toxins. These results suggest that the transgenic cotton, Gossypium hirsutum L., expressing CrylAc and Cry2Ab genes may be deployed for management of CrylAc resistant H. armigera. 相似文献
18.
The influx of K+(86Rb+) into intact roots of rye (Secale cereale L. cv. Rheidal) exposed to a differential temperature (DT) between the root (8° C) and shoot (20° C) is initially reduced compared with warm-grown (WG) controls with both shoot and root maintained at 20° C. Over a period of 3 d, however, K+-influx rates into DT plants are restored to levels similar to or greater than those of the WG controls, the absolute rates of K+ influx being strongly dependent upon the shoot/root ratio. Acclimation in DT plants results in a reduction of K+ influx into the apical (0–2 cm) region of the seminal root which is associated with a compensatory increase in K+ influx into the more mature, basal regions of the root. Values of V
max and apparent K
m for K+ influx into DT plants were similar to those for WG plants at assay temperatures of 8° C and 20° C except for an increase in the apparent K
m at 8° C. The influx of K+ from solutions containing 0.6 mol·m-3 K+ into both WG and DT plants was found to be linearly related to assay temperature over the range 2–27° C, and the temperature sensitivity of K+ influx to be dependent upon shoot/root ratio. At high shoot/root ratios, the ratio of K+ influx at 20° C:K+ influx at 8° C for WG plants approached a minimum value of 1.9 whereas that for DT plants approached unity indicating that K+ influx into DT plants has a large temperature-insensitive component. Additionally, when plants were grown in solutions of low potassium concentration, K+ influx into DT plants was consistently greater than that into WG plants, in spite of having a greater root potassium concentration ([K+]int). This result indicates some change in the regulation of K+ influx by [K+]int in plants exposed to low root temperatures. We suggest that K+ influx into rye seedlings exposed to low root temperatures is regulated by the increased demand placed on the root system by a proportionally larger shoot and that the acclimation of K+ influx to low temperatures may be the result of an increased hydraulic conductivity of the root system.Abbreviations DT
differential temperature pretreatment
- [K+]int
root potassium concentration
- [K+]ext
potassium concentration of nutrient medium
- WG
warm-grown pretreatment 相似文献
19.
Cry1Ab protein levels in phytophagous insects feeding on transgenic corn: implications for secondary exposure risk assessment 总被引:10,自引:0,他引:10
Graham Head Christopher R. Brown Mark E. Groth Jian J. Duan 《Entomologia Experimentalis et Applicata》2001,99(1):37-45
Enzyme-linked immunosorbent assays (ELISA) and bioassays were used to estimate levels of Cry1Ab protein in four species of phytophagous insects after feeding on transgenic Bt-corn plants expressing Cry1Ab protein or artificial diets containing Cry1Ab protein. The level of Cry1Ab in insects feeding on sources containing the Cry1Ab protein was uniformly low but varied with insect species as well as food source. For the corn leaf aphid, Rhopalosiphum maidis (Fitch), feeding on diet solutions containing Cry1Ab protein, the level of the protein in the aphid was 250–500 times less than the original levels in the diet, whereas no Cry1Ab was detected by ELISA in aphids feeding on transgenic Bt-Corn plants. For the lepidopteran insects, Ostrinia nubilalis (Hübner), Helicoverpa zea (Boddie), and Agrotis ipsilon (Hufnagel), levels of Cry1Ab in larvae varied significantly with feeding treatment. When feeding for 24 h on artificial diets containing 20 and 100 ppm of Cry1Ab, the level of Cry1Ab in the larvae was about 57 and 142 times lower, respectively, than the original protein level in the diet for O. nubilalis, 20 and 34 times lower for H. zea, and 10 to 14 times lower for A. ipsilon. Diet incorporation bioassays with a susceptible insect (first instar O. nubilalis) showed significant Cry1Ab bioactivity present within whole body tissues of R. maidis and O. nubilalis that had fed on diet containing a minimum of 20 ppm or higher concentrations (100 or 200 ppm) of Cry1Ab, but no significant bioactivity within the tissues of these insects after feeding on transgenic Bt-corn plants. The relevance of these findings to secondary exposure risk assessment for transgenic Bt crops is discussed. 相似文献
20.
Potential of the Bacillus thuringiensis Toxin Reservoir for the Control of Lobesia botrana (Lepidoptera: Tortricidae), a Major Pest of Grape Plants
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Iigo Ruiz de Escudero Anna Estela Baltasar Escriche Primitivo Caballero 《Applied microbiology》2007,73(1):337-340
The potential of Bacillus thuringiensis Cry proteins to control the grape pest Lobesia botrana was explored by testing first-instar larvae with Cry proteins belonging to the Cry1, Cry2, and Cry9 groups selected for their documented activities against Lepidoptera. Cry9Ca, a toxin from B. thuringiensis, was the protein most toxic to L. botrana larvae, followed in decreasing order by Cry2Ab, Cry1Ab, Cry2Aa, and Cry1Ia7, with 50% lethal concentration values of 0.09, 0.1, 1.4, 3.2, and 8.5 μg/ml of diet, respectively. In contrast, Cry1Fa and Cry1JA were not active at the assayed concentration (100 μg/ml). In vitro binding and competition experiments showed that none of the toxins tested (Cry1Ia, Cry2Aa, Cry2Ab, and Cry9C) shared binding sites with Cry1Ab. We conclude that either Cry1Ia or Cry9C could be used in combination with Cry1Ab to control this pest, either as the active components of B. thuringiensis sprays or expressed together in transgenic plants. 相似文献