scholarly journals Cadherin repeat 5 mutation associated with Bt resistance in a field-derived strain of pink bollworm

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Ling Wang ◽  
Yuemin Ma ◽  
Wei Wei ◽  
Peng Wan ◽  
Kaiyu Liu ◽  
...  
Keyword(s):  
Brush Border Membrane ◽  
Insect Cells ◽  
Transcript Abundance ◽  
Pink Bollworm ◽  
Cross Resistance ◽  
Bt Cotton ◽  
Wild Type ◽  
Bt Toxin ◽  
Bt Resistance ◽  
Evolution Of Resistance

Abstract 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.

scholarly journals Pink Bollworm Resistance to Bt Toxin Cry1Ac Associated with an Insertion in Cadherin Exon 20

Toxins ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 186 ◽  
Author(s):  
Ling Wang ◽  
Yuemin Ma ◽  
Xueqin Guo ◽  
Peng Wan ◽  
Kaiyu Liu ◽  
...  
Keyword(s):  
Insect Pests ◽  
Stop Codon ◽  
Premature Stop Codon ◽  
Pink Bollworm ◽  
Cross Resistance ◽  
Bt Cotton ◽  
Wild Type ◽  
Bt Toxin ◽  
Exon 20 ◽  
In Cells

Insecticidal proteins from Bacillus thuringiensis (Bt) are widely used to control insect pests, but their efficacy is reduced when pests evolve resistance. We report on a novel allele (r16) of the cadherin gene (PgCad1) in pink bollworm (Pectinophora gossypiella) associated with resistance to Bt toxin Cry1Ac, which is produced by transgenic cotton. The r16 allele isolated from a field population in China has 1545 base pairs of a degenerate transposon inserted in exon 20 of PgCad1, which generates a mis-spliced transcript containing a premature stop codon. A strain homozygous for r16 had 300-fold resistance to Cry1Ac, 2.6-fold cross-resistance to Cry2Ab, and completed its life cycle on transgenic Bt cotton producing Cry1Ac. Inheritance of Cry1Ac resistance was recessive and tightly linked with r16. Compared with transfected insect cells expressing wild-type PgCad1, cells expressing r16 were less susceptible to Cry1Ac. Recombinant cadherin protein was transported to the cell membrane in cells transfected with the wild-type PgCad1 allele, but not in cells transfected with r16. Cadherin occurred on brush border membrane vesicles (BBMVs) in the midgut of susceptible larvae, but not resistant larvae. These results imply that the r16 allele mediates Cry1Ac resistance in pink bollworm by interfering with the localization of cadherin.

scholarly journals Hybridizing transgenic Bt cotton with non-Bt cotton counters resistance in pink bollworm

2017 ◽  
Vol 114 (21) ◽  
pp. 5413-5418 ◽  
Author(s):  
Peng Wan ◽  
Dong Xu ◽  
Shengbo Cong ◽  
Yuying Jiang ◽  
Yunxin Huang ◽  
...  
Keyword(s):  
First Generation ◽  
Resistance Management ◽  
Genetically Engineered ◽  
Pink Bollworm ◽  
Bt Cotton ◽  
Bt Toxin ◽  
Random Mixture ◽  
Cotton Plants ◽  
Evolution Of Resistance ◽  
Insecticide Sprays

Extensive cultivation of crops genetically engineered to produce insecticidal proteins from the bacteriumBacillus thuringiensis(Bt) has suppressed some major pests, reduced insecticide sprays, enhanced pest control by natural enemies, and increased grower profits. However, these benefits are being eroded by evolution of resistance in pests. We report a strategy for combating resistance by crossing transgenic Bt plants with conventional non-Bt plants and then crossing the resulting first-generation (F1) hybrid progeny and sowing the second-generation (F2) seeds. This strategy yields a random mixture within fields of three-quarters of plants that produce Bt toxin and one-quarter that does not. We hypothesized that the non-Bt plants in this mixture promote survival of susceptible insects, thereby delaying evolution of resistance. To test this hypothesis, we compared predictions from computer modeling with data monitoring pink bollworm (Pectinophora gossypiella) resistance to Bt toxin Cry1Ac produced by transgenic cotton in an 11-y study at 17 field sites in six provinces of China. The frequency of resistant individuals in the field increased before this strategy was widely deployed and then declined after its widespread adoption boosted the percentage of non-Bt cotton plants in the region. The correspondence between the predicted and observed outcomes implies that this strategy countered evolution of resistance. Despite the increased percentage of non-Bt cotton, suppression of pink bollworm was sustained. Unlike other resistance management tactics that require regulatory intervention, growers adopted this strategy voluntarily, apparently because of advantages that may include better performance as well as lower costs for seeds and insecticides.

scholarly journals Evaluating Cross-Resistance to Cry and Vip Toxins in Four Strains of Helicoverpa armigera With Different Genetic Mechanisms of Resistance to Bt Toxin Cry1Ac

2021 ◽  
Vol 12 ◽  
Author(s):  
Liangxuan Qi ◽  
Hanyang Dai ◽  
Zeng Jin ◽  
Huiwen Shen ◽  
Fang Guan ◽  
...  
Keyword(s):  
Helicoverpa Armigera ◽  
Genetic Basis ◽  
Cross Resistance ◽  
Bt Cotton ◽  
Bt Toxin ◽  
Field Control ◽  
Helicoverpa Armígera ◽  
Genetic Mechanisms ◽  
Evolution Of Resistance ◽  
Control Failures

Evolution of resistance by pests has diminished the efficacy of transgenic crops producing insecticidal proteins from Bacillus thuringiensis (Bt). In China, where transgenic cotton producing Bt toxin Cry1Ac has been planted since 1997, field control failures have not been reported but the frequency of resistance to Cry1Ac has increased in the cotton bollworm, Helicoverpa armigera. This provides incentive to switch to multi-toxin Bt cotton, which is grown in many other countries. Previous work created four laboratory strains of H. armigera with >100-fold resistance to Cry1Ac, with the genetic basis of resistance known in all but the LF256 strain. Here, we analyzed the genetic basis of resistance in Cry1Ac in LF256 and evaluated cross-resistance of all four strains to three toxins produced by widely planted multi-toxin Bt cotton: Cry1Fa, Cry2Ab, and Vip3Aa. DNA sequencing revealed that LF256 lacked the mutations in three genes (HaTSPAN1, HaABCC2, and HaABCC3) that confer resistance to Cry1Ac in two other strains of H. armigera we analyzed. Together with previous results, the data reported here show that each of the four strains examined has a different genetic basis of resistance to Cry1Ac. Significant positive cross-resistance occurred to Cry1Fa in three of the four strains tested but not to Cry2Ab or Vip3Aa in any strain. Thus, Cry2Ab and Vip3Aa are likely to be especially valuable for increasing the efficacy and durability of Bt cotton against H. armigera populations that have some resistance to Cry1Ac.

scholarly journals Two–toxin strategies for management of insecticidal transgenic crops: can pyramiding succeed where pesticide mixtures have not?

1998 ◽  
Vol 353 (1376) ◽  
pp. 1777-1786 ◽  
Author(s):  
R. T. Roush
Keyword(s):  
At Risk ◽  
Insect Pests ◽  
Extended Period ◽  
Transgenic Crops ◽  
Cross Resistance ◽  
Bt Toxin ◽  
Pesticide Mixtures ◽  
Highly Sensitive ◽  
Evolution Of Resistance ◽  
Bt Gene

Transgenic insect–resistant crops that express toxins from Bacillus thuringiensis (Bt) offer significant advantages to pest management, but are at risk of losing these advantages to the evolution of resistance in the targeted insect pests. All commercially available cultivars of these crops carry only a single Bt gene, and are particularly at risk where the targeted insect pests are not highly sensitive to the Bt toxin used. Under such circumstances, the most prudent method of avoiding resistance is to ensure that a large proportion of the pest population develops on non–transgenic ‘refuge’ hosts, generally of the crop itself. This has generated recommendations that 20% or more of the cotton and maize in any given area should be non–transgenic. This may be costly in terms of yields and may encourage further reliance on and resistance to pesticides. The use of two or more toxins in the same variety (pyramiding) can reduce the amount of refuge required to delay resistance for an extended period. Cross–resistance among the toxins appears to have been overestimated as a potential risk to the use of pyramids (and pesticide mixtures) because cross–resistance is at least as important when toxicants are used independently. Far more critical is that there should be nearly 100% mortality of susceptible insects on the transgenic crops. The past failures of pesticide mixtures to manage resistance provide important lessons for the most efficacious deployment of multiple toxins in transgenic crops.

scholarly journals Dual Resistance to Bacillus thuringiensis Cry1Ac and Cry2Aa Toxins in Heliothis virescens Suggests Multiple Mechanisms of Resistance

2003 ◽  
Vol 69 (10) ◽  
pp. 5898-5906 ◽  
Author(s):  
Juan Luis Jurat-Fuentes ◽  
Fred L. Gould ◽  
Michael J. Adang
Keyword(s):  
Bacillus Thuringiensis ◽  
Brush Border ◽  
Heliothis Virescens ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Cross Resistance ◽  
Gene Stacking ◽  
Mechanisms Of Resistance ◽  
Toxin Binding ◽  
Evolution Of Resistance

ABSTRACT One strategy for delaying evolution of resistance to Bacillus thuringiensis crystal (Cry) endotoxins is the production of multiple Cry toxins in each transgenic plant (gene stacking). This strategy relies upon the assumption that simultaneous evolution of resistance to toxins that have different modes of action will be difficult for insect pests. In B. thuringiensis-transgenic (Bt) cotton, production of both Cry1Ac and Cry2Ab has been proposed to delay resistance of Heliothis virescens (tobacco budworm). After previous laboratory selection with Cry1Ac, H. virescens strains CXC and KCBhyb developed high levels of cross-resistance not only to toxins similar to Cry1Ac but also to Cry2Aa. We studied the role of toxin binding alteration in resistance and cross-resistance with the CXC and KCBhyb strains. In toxin binding experiments, Cry1A and Cry2Aa toxins bound to brush border membrane vesicles from CXC, but binding of Cry1Aa was reduced for the KCBhyb strain compared to susceptible insects. Since Cry1Aa and Cry2Aa do not share binding proteins in H. virescens, our results suggest occurrence of at least two mechanisms of resistance in KCBhyb insects, one of them related to reduction of Cry1Aa toxin binding. Cry1Ac bound irreversibly to brush border membrane vesicles (BBMV) from YDK, CXC, and KCBhyb larvae, suggesting that Cry1Ac insertion was unaffected. These results highlight the genetic potential of H. virescens to become resistant to distinct Cry toxins simultaneously and may question the effectiveness of gene stacking in delaying evolution of resistance.

scholarly journals Need for growing non-Bt cotton refugia to overcome Bt resistance problem in targeted larvae of the cotton bollworms, Helicoverpa armigera and Pectinophora gossypiella

2021 ◽  
Vol 31 (1) ◽  
Author(s):  
Muhammad Rafiq Shahid ◽  
Muhammad Farooq ◽  
Muhammad Shakeel ◽  
Misbah Ashraf ◽  
Zia Ullah Zia ◽  
...  
Keyword(s):  
Helicoverpa Armigera ◽  
Larval Mortality ◽  
Pectinophora Gossypiella ◽  
Bt Cotton ◽  
Insect Larvae ◽  
Plant Parts ◽  
Arthropod Species ◽  
Bt Resistance ◽  
American Bollworm ◽  
Helicoverpa Armígera

Abstract Background The effectiveness of Bacillus thuringiensis (Bt) cotton against target arthropod larvae is decreasing day by day. The comparative effect of Bt expression among Bt cotton varieties and different plant parts was observed against the cotton bollworms: Helicoverpa armigera and Pectinophora gossypiella larvae. Results In the present study, larval mortality of H. armigera was higher than P. gossypiella among selected Bt cultivars. Median lethal concentration (LC50) values were 8.91, 13.4, 14.0, and 36.4 for P. gossypiella, while 5.91, 4.04, 2.37, and 8.26 for H. armigera of FH-142, MNH-886, IR-3701, and FH-Lalazar, respectively. These values depicted that P. gossypiella had more Bt resistance problem than H. armigera larvae. The host range of both targeted insect larvae was different from each other due to the polyphagous feeding nature of the larvae of H. armigera that feed on different host plants, but P. gossypiella attacked only cotton with monophagous feeding habit. It was also notable from results that Bt expression in reproductive parts where the attacked pink bollworm was lower than the American bollworm, so the former had the maximum chance of resistance due to repeated exposure to Bt. Conclusions It was concluded that farmers be advised to follow the practice of growing non-Bt as a refuge crop to reduce the problem of Bt resistance in the target arthropod species.

Environmental impact and risk management strategies of Bt cotton commercialization in China

2007 ◽  
Vol 4 (2) ◽  
pp. 93-97 ◽  
Author(s):  
Wu Kong-Ming
Keyword(s):  
Risk Management ◽  
Environmental Impact ◽  
Management Strategies ◽  
Cotton Bollworm ◽  
Bt Cotton ◽  
Resistance Risk ◽  
Factors Associated ◽  
Major Threat ◽  
Risk Management Strategies ◽  
Evolution Of Resistance

AbstractTransgenic cotton expressing the Cry1Ac toxin from Bacillus thuringiensis has been planted widely in China since 1997, and reached 70% of the total cotton area in 2006. The results of monitoring the environmental impact of Bt cotton commercialization indicated that the target pests, cotton bollworm (Helicoverpa armigera) and pink bollworm (Pectinophora gossypiella), were effectively controlled while the mirids (Hemiptera: Miridae) evolved to be key pests in the cotton system. There were no significant changes in resistance gene frequency of field populations of cotton bollworm, but a shift toward increased tolerance was apparent in the area of intensive planting of Bt cotton, indicating that the potential risk of resistance of the target pest has become a major threat for sustainable planting of Bt cotton. Considering the factors associated with the evolution of resistance, risk management strategies are discussed in this paper.

scholarly journals Proteolytic processing of Semliki Forest virus-specific non-structural polyprotein by nsP2 protease

2001 ◽  
Vol 82 (4) ◽  
pp. 765-773 ◽  
Author(s):  
Andres Merits ◽  
Lidia Vasiljeva ◽  
Tero Ahola ◽  
Leevi Kääriäinen ◽  
Petri Auvinen
Keyword(s):  
Mammalian Cells ◽  
Active Sites ◽  
Insect Cells ◽  
Semliki Forest Virus ◽  
Point Mutations ◽  
Proteolytic Processing ◽  
Wild Type ◽  
In Trans ◽  
Polyprotein Precursor

The RNA replicase proteins of Semliki Forest virus (SFV) are translated as a P1234 polyprotein precursor that contains two putative autoproteases. Point mutations introduced into the predicted active sites of both proteases nsP2 (P2) and nsP4 (P4), separately or in combination, completely abolished virus replication in mammalian cells. The effects of these mutations on polyprotein processing were studied by in vitro translation and by expression of wild-type polyproteins P1234, P123, P23, P34 and their mutated counterparts in insect cells using recombinant baculoviruses. A mutation in the catalytic site of the P2 protease, C478A, (P2CA) completely abolished the processing of P12CA34, P12CA3 and P2CA3. Co-expression of P23 and P12CA34 in insect cells resulted in in trans cleavages at the P2/3 and P3/4 sites. Co-expression of P23 and P34 resulted in cleavage at the P3/4 site. In contrast, a construct with a mutation in the active site of the putative P4 protease, D6A, (P1234DA) was processed like the wild-type protein. P34 or its truncated forms were not processed when expressed alone. In insect cells, P4 was rapidly destroyed unless an inhibitor of proteosomal degradation was used. It is concluded that P2 is the only protease needed for the processing of SFV polyprotein P1234. Analysis of the cleavage products revealed that P23 or P2 could not cleave the P1/2 site in trans.

Sign in / Sign up

Export Citation Format

Share Document