Genetic Markers for Western Corn Rootworm Resistance to Bt Toxin

Flagel, Lex; Swarup, Shilpa; Chen, Mao; Bauer, Christopher; Wanjugi, Humphrey; Carroll, Matthew; Hill, Patrick; Tuscan, Meghan; Bansal, Raman; Flannagan, Ronald D.; Clark, Thomas L.; Michel, Andrew P.; Head, Graham P.; Goldman, Barry S.

doi:10.1534/g3.114.016485

Cited by 36 publications

(62 citation statements)

References 32 publications

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“…Similar to previous results with Lepidoptera [34], fragments of this cadherin synergize Cry3Aa and Cry3Bb activity against Diabrotica and Leptinotarsa [35] and the lesser mealworm, Alphitobius diaperinus [36], and a similar result was found for the cadherin from the mealworm, Tenebrio molitor [20]. The demonstration of genetic linkage between an ABC protein and Cry3Bb1 resistance in D. virgifera [16] was the first confirmation from Coleoptera of similar results in Lepidoptera [12,37]. In addition to a linkage analysis, our results add the molecular identity of the mutation in C. tremula , and a demonstration of the role of the CtABCB1 protein in cell killing by the Cry3Aa toxin.…”

Section: Discussionsupporting

confidence: 87%

“…These showed a four-base-pair deletion at position 1561 (GenBank Accession KX686490, Figure S1), introducing a frame shift with a premature stop codon leading to loss of the TpM1 transporter motif as well as the complete second transmembrane domain (Figure 1). A homolog of CtABCB1 in the western corn rootworm, Diabrotica virgifera virgifera , was shown to be genetically linked to resistance to the Bt Cry3Bb1 toxin; however, the resistance-conferring mutation was not reported [16] (Figure S4). The existence of cross-resistance between Cry3Bb1 and mCry3A (a modified version of Cry3Aa) in the western corn rootworm [17] suggested that CtABCB1 could be involved in resistance to Cry3Aa in C. tremula , and we investigated it further.…”

Section: Resultsmentioning

confidence: 99%

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A P-Glycoprotein Is Linked to Resistance to the Bacillus thuringiensis Cry3Aa Toxin in a Leaf Beetle

Pauchet

Bretschneider

Augustin³

et al. 2016

Toxins

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Chrysomela tremula is a polyvoltine oligophagous leaf beetle responsible for massive attacks on poplar trees. This beetle is an important model for understanding mechanisms of resistance to Bacillus thuringiensis (Bt) insecticidal toxins, because a resistant C. tremula strain has been found that can survive and reproduce on transgenic poplar trees expressing high levels of the Cry3Aa Bt toxin. Resistance to Cry3Aa in this strain is recessive and is controlled by a single autosomal locus. We used a larval midgut transcriptome for C. tremula to search for candidate resistance genes. We discovered a mutation in an ABC protein, member of the B subfamily homologous to P-glycoprotein, which is genetically linked to Cry3Aa resistance in C. tremula. Cultured insect cells heterologously expressing this ABC protein swell and lyse when incubated with Cry3Aa toxin. In light of previous findings in Lepidoptera implicating A subfamily ABC proteins as receptors for Cry2A toxins and C subfamily proteins as receptors for Cry1A and Cry1C toxins, this result suggests that ABC proteins may be targets of insecticidal three-domain Bt toxins in Coleoptera as well.

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Section: Discussionsupporting

confidence: 87%

Section: Resultsmentioning

confidence: 99%

A P-Glycoprotein Is Linked to Resistance to the Bacillus thuringiensis Cry3Aa Toxin in a Leaf Beetle

Pauchet

Bretschneider

Augustin³

et al. 2016

Toxins

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“…Similarly, Flagel et al. (, ) found that genetic markers within a QTL for resistance in the Hopkinton strain did not distinguish between other susceptible and resistant field populations of WCR.…”

Section: Discussionmentioning

confidence: 98%

“…Mutations in the ABC transporter sequences in H. virescens and B. mori decreased binding of Cry toxins (Atsumi et al., ; Gahan et al., ) and ABCC2 was found to be one of the genes present in a mapping study of the locus for resistance to Cry1Ac in P. xylostella and T. ni (Baxter et al., ) and in Cry1Fa‐resistant O. nubilalis (Coates & Siegfried, ). A mapping study in WCR also identified a link between Cry3Bb1 resistance and a gene coding for ABCB2 (Flagel et al., ) , an ABC transporter of a different family than the families of ABC transporters identified in Lepidoptera. Moreover, an ABCB2 has been genetically linked to Cry3A resistance and to its mode of action in another Chrysomelid, Chysomela tremula Fabricius (Pauchet et al., ).…”

Section: Discussionmentioning

confidence: 99%

Investigation of Cry3Bb1 resistance and intoxication in western corn rootworm by RNA sequencing

Rault

Siegfried

Gassmann

et al. 2018

J Applied Entomology

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The western corn rootworm (WCR) Diabrotica virgifera virgifera LeConte is a major pest of corn that has evolved resistance to transgenic maize that produces insecticidal Cry toxins. The specific mode of action of Cry3Bb1 and mechanism of resistance in WCR are unknown. This study compared gene expression between Cry3Bb1-susceptible and Cry3Bb1-resistant WCR neonates, in the presence and absence of Cry3Bb1. RNA-Seq data were analyzed to identify differentially expressed transcripts between strains of WCR, providing candidate transcripts for resistance to Cry3Bb1. Constitutive and Cry3Bb1-induced differences between strains caused the differential expression of 608 transcripts after 8 hr. Differentially expressed transcripts between strains included ABC transporters, proteases and α-amylases, which known to be receptors or activators of Cry toxins and involved in resistance to Cry toxins in other insects. The response to Cry3Bb1 treatment resulted in approximately 5,000 differentially expressed transcripts in the susceptible strain and included the same annotation categories found between strains but also included metalloproteases, cadherins and signaling proteins. None of these annotations were identified digitalcommons.unl.edu R a u l t e t a l . i n J o u r n a l o f A p p l i e d E n t o m o l o g y ,2 0 1 8 2in the response of the resistant strain to Cry3Bb1, which was represented by only 12 transcripts. Tissue-specific expression analysis of selected transcripts revealed that an α-amylase and a protease were expressed in the midgut, the target organ of Cry toxins. A protease inhibitor and two ABC transporters were expressed outside the midgut, suggesting a limited role in resistance. Numerous polymorphic sites were identified from the RNA-Seq data that showed allele frequency differences between the resistant and susceptible strains. Analysis of these polymorphisms in a larger set WCR strains suggested that the differences were due to genetic drift rather than being associated with resistance to Cry3Bb1. Polymorphisms identified in genes with known roles in resistance to Cry toxins did not appear to differ in frequency between resistant and susceptible strains.

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“…However, the recently observed resistance of some Lepidoptera and beetle pests has reduced these benefits (9) and is becoming the most serious threat to the continued efficacy of Bt crops. The "pyramided" strategy has been widely used to significantly delay resistance (10,11).…”

mentioning

confidence: 99%

Dissimilar Crystal Proteins Cry5Ca1 and Cry5Da1 Synergistically Act against Meloidogyne incognita and Delay Cry5Ba-Based Nematode Resistance

Geng

Liu

et al. 2017

Appl Environ Microbiol

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Cry proteins of Bacillus thuringiensis (Bt) have been successfully used as biopesticides and in transgenic crops throughout the world. However, resources against the most serious agricultural pathogens, plant root-knot nematodes, are limited. The genomes of several highly nematicidal virulent Bt strains from our laboratory have been sequenced, facilitating the identification of novel Cry proteins and other virulence factors. We identified two novel Cry proteins, Cry5Ca1 and Cry5Da1, that exhibit high toxicity against Meloidogyne incognita. Using the Caenorhabditis elegans model, the two Cry5 toxins were shown to negatively affect nematode life span, fertility, and survival. The 50% lethal concentrations (LC 50 s) of Cry5Ca1 and Cry5Da1 were 57.22 g/ml and 36.69 g/ml, respectively. Moreover, a synergistic effect (synergism factor, 1.61 to 2.04) was observed for nematicidal toxicity of Cry5Ca1 and Cry5Da1, which is accordant with the phylogenetic results suggesting that domain II of the two novel Cry5 toxins evolved into two independent clades. Through comparison of the depressed degree of toxicity in the ␤-methylgalactoside detoxification test, we found that the novel toxin Cry5D possesses a different galactosebinding epitope; meanwhile, the finding that Cry5D does not share a motif (GXXXE) in the corresponding loop of domain II with Cry5B could explain the different galactose binding performance. Additionally, low-level cross-resistance of C. elegans bre mutant strains was evident between Cry5B and Cry5D. These results suggest that Cry5D can be used as an alternative to delay the potential resistance of nematodes to Cry5B. IMPORTANCE Although proper gene resources for Bt crops against the most serious agricultural pathogens, plant root-knot nematodes, are limited, we have identified two novel nematicidal toxins, Cry5Ca1 and Cry5Da1, against M. incognita, which have supplied more gene candidates for Bt crops designed against nematodes. Moreover, the association of the dissimilarity between Cry5Da1 and Cry5Ba1 and their low crossresistance can be attributed not only to a low sequence similarity of domain II but also to the structural difference of the key motif and receptor-binding epitope in the loops. This association facilitates the selection of a proper candidate for the prospective design of pyramided Bt crops that can delay potential resistance.KEYWORDS Bacillus thuringiensis, Caenorhabditis elegans, Cry proteins, bre resistance, nematicidal T he agricultural economic damage caused by more than 4,100 species of plantparasitic nematodes (PPNs) has been estimated to cost US$80 billion per year (1, 2), and a large proportion of this cost is due to the serious damage caused by the plant-parasitic nematode Meloidogyne incognita (3). Although many nematophagous

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Genetic Markers for Western Corn Rootworm Resistance to Bt Toxin

Cited by 36 publications

References 32 publications

A P-Glycoprotein Is Linked to Resistance to the Bacillus thuringiensis Cry3Aa Toxin in a Leaf Beetle

A P-Glycoprotein Is Linked to Resistance to the Bacillus thuringiensis Cry3Aa Toxin in a Leaf Beetle

Investigation of Cry3Bb1 resistance and intoxication in western corn rootworm by RNA sequencing

Dissimilar Crystal Proteins Cry5Ca1 and Cry5Da1 Synergistically Act against Meloidogyne incognita and Delay Cry5Ba-Based Nematode Resistance

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