Mutated Cadherin Alleles from a Field Population of
            <i>Helicoverpa armigera</i>
            Confer Resistance to
            <i>Bacillus thuringiensis</i>
            Toxin Cry1Ac

Yang, Yajun; Chen, Haiyan; Wu, Yingliang; Yang, Yihua; Wu, Shuwen

doi:10.1128/aem.01703-07

Cited by 89 publications

(89 citation statements)

References 26 publications

(36 reference statements)

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“…However, the lack of an APN in S. exigua leads to resistance to Cry1C (62), which indicates that the APN also plays an important role in the intoxication pathway of Cry1C. Moreover, the midgut cadherin is a known midgut receptor for Cry1A toxins, and mutations of the midgut cadherin gene have been identified to be associated with high-level resistance to Cry1Ac in H. virescens, P. gossypiella, and H. armigera (9,12,14,63). Similarly, Cry3, Cry4, and Cry11 toxins also bind to the midgut cadherin in their target insects (64)(65)(66)(67), and it has been well documented that a fragment of the midgut cadherin from target insects could synergize the toxicity of Cry toxins from different groups, including in Cry1A, Cry1C, Cry3A, Cry3B, Cry4B, and Cry8C, in insects from Lepidoptera, Coleoptera, and Diptera (67)(68)(69)(70)(71)(72).…”

Section: Discussionmentioning

confidence: 99%

“…Studies of insect resistance to Bt toxins have so far been mostly on Lepidoptera pests to the toxin Cry1Ab or Cry1Ac (9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19), the two major Bt Cry toxins which are highly toxic to Lepidoptera pests and known to share the same binding sites in target insects (4,20). Cry1Ab and Cry1Ac are the primary insecticidal proteins expressed in the current commercial transgenic Bt maize and Bt cotton varieties to target Lepidoptera pests in the field (21).…”

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Resistance to Bacillus thuringiensis Toxin Cry2Ab in Trichoplusia ni Is Conferred by a Novel Genetic Mechanism

Song

Kain

Cassidy

et al. 2015

Appl Environ Microbiol

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The resistance to the Bacillus thuringiensis (Bt) toxin Cry2Ab in a greenhouse-originated Trichoplusia ni strain resistant to both Bt toxins Cry1Ac and Cry2Ab was characterized. Biological assays determined that the Cry2Ab resistance in the T. ni strain was a monogenic recessive trait independent of Cry1Ac resistance, and there existed no significant cross-resistance between Cry1Ac and Cry2Ab in T. ni. From the dual-toxin-resistant T. ni strain, a strain resistant to Cry2Ab only was isolated, and the Cry2Ab resistance trait was introgressed into a susceptible laboratory strain to facilitate comparative analysis of the Cry2Ab resistance with the susceptible T. ni strain. Results from biochemical analysis showed no significant difference between the Cry2Ab-resistant and -susceptible T. ni larvae in midgut proteases, including caseinolytic proteolytic activity and zymogram profile and serine protease activities, in midgut aminopeptidase and alkaline phosphatase activity, and in midgut esterases and hemolymph plasma melanization activity. For analysis of genetic linkage of Cry2Ab resistance with potential Cry toxin receptor genes, molecular markers for the midgut cadherin, alkaline phosphatase (ALP), and aminopeptidase N (APN) genes were identified between the original greenhouse-derived dual-toxin-resistant and the susceptible laboratory T. ni strains. Genetic linkage analysis showed that the Cry2Ab resistance in T. ni was not genetically associated with the midgut genes coding for the cadherin, ALP, and 6 APNs (APN1 to APN6) nor associated with the ABC transporter gene ABCC2. Therefore, the Cry2Ab resistance in T. ni is conferred by a novel but unknown genetic mechanism.T he Gram-positive soil bacterium Bacillus thuringiensis (Bt) has been widely used as a microbial insecticide in sprayable formulations, and Bt toxins are the primary insecticidal proteins expressed in genetically engineered crops to confer insect resistance (1; ISAAA's GM Approval Database, http://www.isaaa.org /gmapprovaldatabase/). Since the mid-1990s, insect-resistant Bt crops have been rapidly adopted with proven economic and environmental benefits (2, 3). However, development of insect resistance to Bt toxins threatens the long-term success of application of Bt toxins for insect pest control. The genetic potential of insect populations to evolve Bt resistance has been well shown in laboratory selections, and cases of insect resistance to Bt formulations and Bt crops have occurred in insect populations under selection pressure by Bt sprays and Bt crops in the field (4-8).Studies of insect resistance to Bt toxins have so far been mostly on Lepidoptera pests to the toxin Cry1Ab or Cry1Ac (9-19), the two major Bt Cry toxins which are highly toxic to Lepidoptera pests and known to share the same binding sites in target insects (4, 20). Cry1Ab and Cry1Ac are the primary insecticidal proteins expressed in the current commercial transgenic Bt maize and Bt cotton varieties to target Lepidoptera pests in the field (21). Resistance to Cry1Ac and Cry1Ab ...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Resistance to Bacillus thuringiensis Toxin Cry2Ab in Trichoplusia ni Is Conferred by a Novel Genetic Mechanism

Song

Kain

Cassidy

et al. 2015

Appl Environ Microbiol

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“…Screening performed in this study revealed two novel polymorphisms in the cqm1 gene, 16-and 25-nt deletions found at the same region which encompasses the 19-nt deletion originally found in cqm1 REC . The finding of one homozygous larva sample for cqm1 in the JAB population was not expected, considering its status of being a nontreated population, since data from a previous screening of B. sphaericus and Bt resistance alleles have shown such alleles only in heterozygous individuals under such conditions (4,42,45). The resistance phenotype conferred by cqm1 REC-D16 and cqm1 REC-D25 alleles could not be experimentally confirmed; nevertheless, the functional effect of these deletions on larva susceptibility is likely similar to that of cqm1 REC , since they all provoke frameshifts and introduce the same premature stop codon in the sequence, which prevents the expression of fulllength GPI-anchored proteins (6,8,29).…”

Section: Discussionmentioning

confidence: 99%

Novel Mutations Associated with Resistance to Bacillus sphaericus in a Polymorphic Region of the Culex quinquefasciatus cqm1 Gene

Chalegre

Romão

Tavares

et al. 2012

Appl Environ Microbiol

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Bin toxin from Bacillus sphaericus acts on Culex quinquefasciatus larvae by binding to Cqm1 midgut-bound receptors, and disruption of the cqm1 gene is the major cause of resistance. The goal of this work was to screen for a laboratory-selected resistance cqm1 REC allele in field populations in the city of Recife, Brazil, and to describe other resistance-associated polymorphisms in the cqm1 gene. The cqm1 REC allele was detected in the four nontreated populations surveyed at frequencies from 0.001 to 0.017, and sequence analysis from these samples revealed a novel resistant allele (cqm1 REC-D16 ) displaying a 16-nucletotide (nt) deletion which is distinct from the 19-nt deletion associated with cqm1 REC . Yet a third resistant allele (cqm1 REC-D25 ), displaying a 25-nt deletion, was identified in samples from a treated area exposed to B. sphaericus. A comparison of the three deletion events revealed that all are located within the same 208-nt region amplified during the screening procedure. They also introduce equivalent frameshifts in the sequence and generate the same premature stop codon, leading to putative transcripts encoding truncated proteins which are unable to locate to the midgut epithelium. The populations analyzed in this study contained a variety of alleles with mutations disrupting the function of the corresponding Bin toxin receptor. Their locations reveal a hot spot that can be exploited to assess the resistance risk through DNA screening.T he utilization of biolarvicides based on Bacillus sphaericus requires monitoring strategies which can predict or prevent potential resistance selection among exposed mosquito populations. The binary (Bin) crystal toxin, which is the major active insecticidal factor found in commercial B. sphaericus strains, acts on mosquito larvae after ingestion, processing and binding to specific receptors located on the midgut epithelium (5, 24). Bin toxin displays high activity against larvae of the Culex pipiens complex and B. sphaericus has an excellent persistence under field conditions, which make this an effective biolarvicide for controlling these species in urban areas (17). However, the mode of action of Bin toxin relies entirely on its binding to a single class of midgut receptors which are glycosylphosphatidylinositol (GPI)-anchored ␣-glucosidases named Cpm1 and Cqm1 for Culex pipiens and Culex quinquefasciatus, respectively (7,29,30). Failure of toxins to bind to their midgut receptors has been described, in a wide range of target insects, as the primary resistance mechanism to insecticidal proteins from entomopathogenic bacteria (11,16,25). In the case of B. sphaericus, this is a critical aspect since resistance cases have also been reported after laboratory selection or field exposure (2,25,27,36,38,44).Investigation of the B. sphaericus resistance mechanisms has confirmed the essential role for the binding of Bin toxin to its receptors, since mutations within the cpm1/cqm1 genes, which are recessively inherited, are the major causes leading to the absence of ...

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“…6-7 million ha), including the Mato Grosso do Sul, PR, SC, and RS states neighbouring Paraguay, Argentina, and Uruguay. Resistances to Cry1Ac toxins in H. armigera are known to occur in China (Yang et al, 2007) and India (Kranthi et al, 2006), and it is important to note that the majority of the soybean crops planted in the Cone Sul region are GM plants expressing the Cry1Ac toxin. Bt corn expressing the Cry2Ab toxin is also cultivated in the Cone Sul region and monitoring of H. armigera will also need to consider resistance to Cry2Ab .…”

Section: Discussionmentioning

confidence: 99%

Mitochondrial DNA COI characterization of Helicoverpa armigera (Lepidoptera: Noctuidae) from Paraguay and Uruguay

Arnemann¹,

James²,

Walsh³

et al. 2016

Genet. Mol. Res.

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ABSTRACT. Since its detection in Brazil in 2013, the Old World cotton bollworm Helicoverpa armigera has been reported in Argentina, Paraguay, and Bolivia. Here we present evidence extending the South American range of H. armigera to Uruguay, using polymerase chain reaction and sequencing of the partial mitochondrial DNA (mtDNA) cytochrome oxidase I region. Molecular characterization of this gene region from individuals from Paraguay also supports previous morphological identification of H. armigera in Paraguay. Shared mtDNA haplotypes in H. armigera from Brazil, Uruguay, and Paraguay were identified. Additional surveying of populations in this region will be imperative to better monitor and understand factors that are underpinning its presence and successful adaptation in these South American regions. We discuss our findings with respect to the development of resistance pest management strategies of this invasive insect pest in a predominantly monoculture soybean crop landscape in the Southern Cone region.

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Mutated Cadherin Alleles from a Field Population of Helicoverpa armigera Confer Resistance to Bacillus thuringiensis Toxin Cry1Ac

Cited by 89 publications

References 26 publications

Resistance to Bacillus thuringiensis Toxin Cry2Ab in Trichoplusia ni Is Conferred by a Novel Genetic Mechanism

Resistance to Bacillus thuringiensis Toxin Cry2Ab in Trichoplusia ni Is Conferred by a Novel Genetic Mechanism

Novel Mutations Associated with Resistance to Bacillus sphaericus in a Polymorphic Region of the Culex quinquefasciatus cqm1 Gene

Mitochondrial DNA COI characterization of Helicoverpa armigera (Lepidoptera: Noctuidae) from Paraguay and Uruguay

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