scholarly journals Novel genetic basis of resistance to Bt toxin Cry1Ac in Helicoverpa zea

2021 ◽  
Author(s):  
Kyle M Benowitz ◽  
Carson W Allan ◽  
Benjamin A Degain ◽  
Xianchun Li ◽  
Jeffrey A Fabrick ◽  
...  
Keyword(s):  
Helicoverpa Zea ◽  
Genetic Basis ◽  
Stop Codon ◽  
Premature Stop Codon ◽  
Pest Resistance ◽  
The United States ◽  
Chromosome 13 ◽  
Bt Toxin ◽  
Bt Toxins ◽  
A Genome

Crops genetically engineered to produce insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) have advanced pest management, but their benefits are diminished when pests evolve resistance. Elucidating the genetic basis of pest resistance to Bt toxins can improve resistance monitoring, resistance management, and design of new insecticides. Here, we investigated the genetic basis of resistance to Bt toxin Cry1Ac in the lepidopteran Helicoverpa zea, one of the most damaging crop pests in the United States. To facilitate this research, we built the first chromosome-level genome assembly for this species. Using a genome-wide association study, fine-scale mapping, and RNA-seq, we identified a 250kb QTL on chromosome 13 that was strongly associated with resistance in a strain of H. zea that had been selected for resistance in the field and lab. This QTL contains no genes with a previously reported role in resistance or susceptibility to Bt toxins. However, within this QTL, we discovered a premature stop codon in a kinesin gene. We hypothesize that this mutation contributes to resistance. The results indicate the mutation on chromosome 13 was necessary but not sufficient for resistance, and therefore conclude that mutations in more than one gene contributed to resistance. Moreover, we found no changes in gene sequence or expression consistently associated with resistance for 11 genes previously implicated in lepidopteran resistance to Cry1Ac. Thus, the results reveal a novel and polygenic basis of resistance and extend the list of genes contributing to pest resistance to Bt toxins.

scholarly journals Early Warning of Resistance to Bt Toxin Vip3Aa in Helicoverpa zea

Toxins ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 618
Author(s):  
Fei Yang ◽  
David L. Kerns ◽  
Nathan S. Little ◽  
José C. Santiago González ◽  
Bruce E. Tabashnik
Keyword(s):  
Early Warning ◽  
Helicoverpa Zea ◽  
The United States ◽  
Genetically Engineered ◽  
Bt Toxin ◽  
Bt Toxins ◽  
Evolution Of Resistance ◽  
Reported Data ◽  
Lepidopteran Pest ◽  
Urgent Action

Evolution of resistance by pests can reduce the benefits of crops genetically engineered to produce insecticidal proteins from Bacillus thuringiensis (Bt). Because of the widespread resistance of Helicoverpa zea to crystalline (Cry) Bt toxins in the United States, the vegetative insecticidal protein Vip3Aa is the only Bt toxin produced by Bt corn and cotton that remains effective against some populations of this polyphagous lepidopteran pest. Here we evaluated H. zea resistance to Vip3Aa using diet bioassays to test 42,218 larvae from three lab strains and 71 strains derived from the field during 2016 to 2020 in Arkansas, Louisiana, Mississippi, Tennessee, and Texas. Relative to the least susceptible of the three lab strains tested (BZ), susceptibility to Vip3Aa of the field-derived strains decreased significantly from 2016 to 2020. Relative to another lab strain (TM), 7 of 16 strains derived from the field in 2019 were significantly resistant to Vip3Aa, with up to 13-fold resistance. Susceptibility to Vip3Aa was significantly lower for strains derived from Vip3Aa plants than non-Vip3Aa plants, providing direct evidence of resistance evolving in response to selection by Vip3Aa plants in the field. Together with previously reported data, the results here convey an early warning of field-evolved resistance to Vip3Aa in H. zea that supports calls for urgent action to preserve the efficacy of this toxin.

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 Revelation by Single-Nucleotide Polymorphism Genotyping That Mutations Leading to a Premature Stop Codon in inlA Are Common among Listeria monocytogenes Isolates from Ready-To-Eat Foods but Not Human Listeriosis Cases

2010 ◽  
Vol 76 (9) ◽  
pp. 2783-2790 ◽  
Author(s):  
A. Van Stelten ◽  
J. M. Simpson ◽  
T. J. Ward ◽  
K. K. Nightingale
Keyword(s):  
United States ◽  
Single Nucleotide Polymorphism ◽  
Listeria Monocytogenes ◽  
Stop Codon ◽  
Human Health Risk ◽  
Premature Stop Codon ◽  
The United States ◽  
Nucleotide Polymorphism ◽  
Pathogenic Potential ◽  
Single Nucleotide

ABSTRACT Listeria monocytogenes utilizes internalin A (InlA; encoded by inlA) to cross the intestinal barrier to establish a systemic infection. Multiple naturally occurring mutations leading to a premature stop codon (PMSC) in inlA have been reported worldwide, and these mutations are causally associated with attenuated virulence. Five inlA PMSC mutations recently discovered among isolates from France and the United States were included as additional markers in our previously described inlA single-nucleotide polymorphism (SNP) genotyping assay. This assay was used to screen >1,000 L. monocytogenes isolates from ready-to-eat (RTE) foods (n = 502) and human listeriosis cases (n = 507) for 18 inlA PMSC mutations. A significantly (P < 0.0001) greater proportion of RTE food isolates (45.0%) carried a PMSC mutation in inlA compared to human clinical isolates (5.1%). The proportion of L. monocytogenes with or without PMSC mutations in inlA was similar among isolates from different RTE food categories except for deli meats, which included a marginally higher proportion (P = 0.12) of isolates carrying a PMSC in inlA. We also analyzed the distribution of epidemic clone (EC) strains, which have been linked to the majority of listeriosis outbreaks worldwide and are overrepresented among sporadic cases in the United States. We observed a significant (P < 0.05) overrepresentation of EC strains in deli and seafood salads and a significant (P < 0.05) underrepresentation of EC strains in smoked seafood. These results provide important data to predict the human health risk of exposure to L. monocytogenes strains that differ in pathogenic potential through consumption of contaminated RTE foods.

scholarly journals CRISPR-mediated mutations in the ABC transporter gene ABCA2 confer pink bollworm resistance to Bt toxin Cry2Ab

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jeffrey A. Fabrick ◽  
Dannialle M. LeRoy ◽  
Lolita G. Mathew ◽  
Yidong Wu ◽  
Gopalan C. Unnithan ◽  
...  
Keyword(s):  
Genetic Basis ◽  
Insect Pests ◽  
Pest Resistance ◽  
Genetically Engineered ◽  
Pink Bollworm ◽  
Specific Gene ◽  
Gene Encoding ◽  
Bt Crops ◽  
Bt Toxin ◽  
First Case

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

scholarly journals The Genetics and Evolution of Eye Color in Domestic Pigeons (Columba livia)

2020 ◽  
Author(s):  
Si Si ◽  
Xiao Xu ◽  
Yan Zhuang ◽  
Xiaodong Gao ◽  
Honghai Zhang ◽  
...  
Keyword(s):  
Glucose Transporter ◽  
Genome Wide Association Study ◽  
Stop Codon ◽  
Phylogenetic Analyses ◽  
Premature Stop Codon ◽  
Columba Livia ◽  
Eye Color ◽  
Iris Color ◽  
A Genome ◽  
Domestic Pigeons

The avian eye color, generally referred to the color of the iris, results from both pigments and structural coloration. Avian iris colors exhibit striking interspecific and, in some domestic species, intraspecific variations, suggesting unique evolutionary and ecological histories. Here we tackled the genetic basis of the pearl (white) iris color in domestic pigeons (Columba livia), to elucidate the largely unknown genetic mechanism underlying the evolution of avian iris coloration. Using a genome-wide association study (GWAS) in 92 pigeons, we mapped the pearl iris trait to a 9 kb region and a facilitative glucose transporter gene SLC2A11B. A nonsense mutation W49X leading to a premature stop codon in SLC2A11B was identified as the causal variant. Transcriptome analysis suggested that SLC2A11B loss-of-function may downregulate the xanthophore-differentiation gene CSF1R, and a key gene GCH1 involved in biosynthesis of pteridine, whose absence results in pearl iris. Coalescence and phylogenetic analyses indicated the mutation originated about 5,400 years ago coinciding with the onset of pigeon domestication, while positive selection was detected likely associated with artificial breeding. Within Aves, potentially impaired SLC2A11B was found in 10 species from six distinct lineages correlated to their signature brown or blue eyes. Analysis of vertebrate SLC2A11B orthologs revealed relaxed selection in the avian clade, consistent with the scenario that, during and after avian divergence from reptile ancestor, the SLC2A11B-involved development of dermal chromatophores likely degenerated due to feather coverage. Our findings provide new insight into the mechanism of avian iris color variations and the evolution of pigmentation in vertebrates.

scholarly journals Identification of the Genetic Basis for Clinical Menadione-Auxotrophic Small-Colony Variant Isolates of Staphylococcus aureus

2008 ◽  
Vol 52 (11) ◽  
pp. 4017-4022 ◽  
Author(s):  
Jonas Lannergård ◽  
Christof von Eiff ◽  
Gunnar Sander ◽  
Tina Cordes ◽  
Jochen Seggewiβ ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Antibiotic Therapy ◽  
Hemolytic Activity ◽  
Genetic Basis ◽  
Stop Codon ◽  
Premature Stop Codon ◽  
Normal Growth ◽  
Gene Encoding ◽  
Systemic Antibiotic Therapy ◽  
Small Colony

ABSTRACT Small-colony variants (SCVs) of Staphylococcus aureus are associated with persistent infections and may be selectively enriched during antibiotic therapy. Three pairs of clonally related S. aureus isolates were recovered from patients receiving systemic antibiotic therapy. Each pair consisted of an isolate with a normal phenotype and an isolate with an SCV phenotype. These SCVs were characterized by reduced susceptibility to gentamicin, reduced hemolytic activity, slow growth, and menadione auxotrophy. Sequencing of the genes involved in menadione biosynthesis revealed mutations in menB, the gene encoding naphthoate synthase, in all three strains with the SCV phenotype. The menB mutations were (i) a 9-bp deletion from nucleotides 55 to 63, (ii) a frameshift mutation that resulted in a premature stop codon at position 230, and (iii) a point mutation that caused the amino acid substitution Gly to Val at codon 233. Fluctuation tests showed that growth-compensated mutants arose in the SCV population of one strain, strain OM1b, at a rate of 1.8 × 10−8 per cell per generation. Sequence analyses of 23 independently isolated growth-compensated mutants of this strain revealed alterations in the menB sequence in every case. These alterations included reversions to the wild-type sequence and intragenic second-site mutations. Each of the growth-compensated mutants showed a restoration of normal growth and a loss of menadione auxotrophy, increased susceptibility to gentamicin, and restored hemolytic activity. These data show that mutations in menB cause the SCV phenotype in these clinical isolates. This is the first report on the genetic basis of menadione-auxotrophic SCVs determined in clinical S. aureus isolates.

scholarly journals The genetics and evolution of eye color in domestic pigeons (Columba livia)

PLoS Genetics ◽  
2021 ◽  
Vol 17 (8) ◽  
pp. e1009770
Author(s):  
Si Si ◽  
Xiao Xu ◽  
Yan Zhuang ◽  
Xiaodong Gao ◽  
Honghai Zhang ◽  
...  
Keyword(s):  
Glucose Transporter ◽  
Genome Wide Association Study ◽  
Stop Codon ◽  
Phylogenetic Analyses ◽  
Premature Stop Codon ◽  
Columba Livia ◽  
Eye Color ◽  
Iris Color ◽  
A Genome ◽  
Domestic Pigeons

The eye color of birds, generally referring to the color of the iris, results from both pigmentation and structural coloration. Avian iris colors exhibit striking interspecific and intraspecific variations that correspond to unique evolutionary and ecological histories. Here, we identified the genetic basis of pearl (white) iris color in domestic pigeons (Columba livia) to explore the largely unknown genetic mechanism underlying the evolution of avian iris coloration. Using a genome-wide association study (GWAS) in 92 pigeons, we mapped the pearl iris trait to a 9 kb region containing the facilitative glucose transporter gene SLC2A11B. A nonsense mutation (W49X) leading to a premature stop codon in SLC2A11B was identified as the causal variant. Transcriptome analysis suggested that SLC2A11B loss of function may downregulate the xanthophore-differentiation gene CSF1R and the key pteridine biosynthesis gene GCH1, thus resulting in the pearl iris phenotype. Coalescence and phylogenetic analyses indicated that the mutation originated approximately 5,400 years ago, coinciding with the onset of pigeon domestication, while positive selection was likely associated with artificial breeding. Within Aves, potentially impaired SLC2A11B was found in six species from six distinct lineages, four of which associated with their signature brown or blue eyes. Analysis of vertebrate SLC2A11B orthologs revealed relaxed selection in the avian clade, consistent with the scenario that during and after avian divergence from the reptilian ancestor, the SLC2A11B-involved development of dermal chromatophores likely degenerated in the presence of feather coverage. Our findings provide new insight into the mechanism of avian iris color variations and the evolution of pigmentation in vertebrates.

scholarly journals Significant Shift in Median Guinea Pig Infectious Dose Shown by an Outbreak-AssociatedListeria monocytogenesEpidemic Clone Strain and a Strain Carrying a Premature Stop Codon Mutation ininlA

2011 ◽  
Vol 77 (7) ◽  
pp. 2479-2487 ◽  
Author(s):  
A. Van Stelten ◽  
J. M. Simpson ◽  
Y. Chen ◽  
V. N. Scott ◽  
R. C. Whiting ◽  
...  
Keyword(s):  
Dose Response ◽  
Guinea Pigs ◽  
Stop Codon ◽  
Premature Stop Codon ◽  
The United States ◽  
Risk Assessments ◽  
Significant Shift ◽  
Infectious Dose ◽  
Internalin A ◽  
E Cadherin

ABSTRACTListeria monocytogenescontains (i) epidemic clone (EC) strains, which have been linked to the majority of listeriosis outbreaks worldwide and are overrepresented among sporadic cases in the United States, and (ii) strains commonly isolated from ready-to-eat foods that carry a mutation leading to a premature stop codon (PMSC) ininlA, which encodes the key virulence factor internalin A (InlA). Internalin A binds certain isoforms of the cellular receptor E-cadherin to facilitate crossing the intestinal barrier during the initial stages of anL. monocytogenesinfection. Juvenile guinea pigs, which express the human isoform of E-cadherin that binds InlA, were intragastrically challenged with a range of doses of (i) an EC strain associated with a listeriosis outbreak or (ii) a strain carrying a PMSC mutation ininlA. Recovery ofL. monocytogenesfrom tissues (i.e., liver, spleen, mesenteric lymph nodes, and ileum) was used to develop strain-specific dose-response curves on the basis of individual and combined organ data. Modeling of individual and combined organ data revealed an approximate 1.2 to 1.3 log10increase in the median infectious dose for the strain carrying a PMSC ininlArelative to that for the EC strain. Inclusion of the strain parameter significantly improved the goodness of fit for individual and combined organ models, indicating a significant shift in median infectious dose for guinea pigs challenged with aninlAPMSC strain compared to that for guinea pigs challenged with an EC strain. Results from this work provide evidence that theL. monocytogenesdose-response relationship is strain specific and will provide critical data for enhancement of current risk assessments and development of future risk assessments.

Ectopic Transcript Analysis Indicates that Allelic Exclusion is an Important Cause of Type I Protein C Deficiency in Patients with Nonsense and Frameshift Mutations in the PROC Gene

1996 ◽  
Vol 75 (06) ◽  
pp. 870-876 ◽  
Author(s):  
José Manuel Soria ◽  
Lutz-Peter Berg ◽  
Jordi Fontcuberta ◽  
Vijay V Kakkar ◽  
Xavier Estivill ◽  
...  
Keyword(s):  
Splice Site ◽  
Protein C ◽  
Stop Codon ◽  
Premature Stop Codon ◽  
Allelic Exclusion ◽  
Polymorphism Analysis ◽  
Type I ◽  
Protein C Deficiency ◽  
Nonsense Mutations ◽  
Stop Codons

SummaryNonsense mutations, deletions and splice site mutations are a common cause of type I protein C deficiency. Either directly or indirectly by altering the reading frame, these' lesions generate or may generate premature stop codons and could therefore be expected to result in premature termination of translation. In this study, the possibility that such mutations could instead exert their pathological effects at an earlier stage in the expression pathway, through “allelic exclusion” at the RNA level, was investigated. Protein C (PROC) mRNA was analysed in seven Spanish type I protein C deficient patients heterozygous for two nonsense mutations, a 7bp deletion, a 2bp insertion and three splice site mutations. Ectopic RNA transcripts from patient and control lymphocytes were analysed by RT-PCR and direct sequencing of amplified PROC cDNA fragments. The nonsense mutations and the deletion were absent from the cDNAs indicating that only mRNA derived from the normal allele had been expressed. Similarly for the splice site mutations, only normal PROC cDNAs were obtained. In one case, exclusion of the mutated allele could be confirmed by polymorphism analysis. In contrast to these six mutations, the 2 bp insertion was not associated with loss of mRNA from the mutated allele. In this case, cDNA analysis revealed the absence of 19 bases from the PROC mRNA consistent with the generation and utilization of a cryptic splice site 3’ to the site of mutation, which would result in a frameshift and a premature stop codon. It is concluded that allelic exclusion is a common causative mechanism in those cases of type I protein C deficiency which result from mutations that introduce premature stop codons

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