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. 2015 Jul 29;16(1):558.
doi: 10.1186/s12864-015-1751-6.

Transcriptional analysis of susceptible and resistant European corn borer strains and their response to Cry1F protoxin

Neetha Nanoth Vellichirammal  1 , Haichuan Wang  2 , Seong-Il Eyun  3 , Etsuko N Moriyama  4 , Brad S Coates  5 , Nicholas J Miller  6 , Blair D Siegfried  7
Affiliations

Transcriptional analysis of susceptible and resistant European corn borer strains and their response to Cry1F protoxin

Neetha Nanoth Vellichirammal et al. BMC Genomics. .

Abstract

Background: Despite a number of recent reports of insect resistance to transgenic crops expressing insecticidal toxins from Bacillus thuringiensis (Bt), little is known about the mechanism of resistance to these toxins. The purpose of this study is to identify genes associated with the mechanism of Cry1F toxin resistance in European corn borer (Ostrinia nubilalis Hübner). For this, we compared the global transcriptomic response of laboratory selected resistant and susceptible O. nubilalis strain to Cry1F toxin. We further identified constitutive transcriptional differences between the two strains.

Results: An O. nubilalis midgut transcriptome of 36,125 transcripts was assembled de novo from 106 million Illumina HiSeq and Roche 454 reads and used as a reference for estimation of differential gene expression analysis. Evaluation of gene expression profiles of midgut tissues from the Cry1F susceptible and resistant strains after toxin exposure identified a suite of genes that responded to the toxin in the susceptible strain (n = 1,654), but almost 20-fold fewer in the resistant strain (n = 84). A total of 5,455 midgut transcripts showed significant constitutive expression differences between Cry1F susceptible and resistant strains. Transcripts coding for previously identified Cry toxin receptors, cadherin and alkaline phosphatase and proteases were also differentially expressed in the midgut of the susceptible and resistant strains.

Conclusions: Our current study provides a valuable resource for further molecular characterization of Bt resistance and insect response to Cry1F toxin in O. nubilalis and other pest species.

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Figures

Fig. 1
Fig. 1
Ortholog hit ratio analysis of the O. nubilalis transcriptome assembly. OHR values for the O. nubilalis transcripts when compared to B. mori sequences. Of the 12,446 O. nubilalis sequences with a BLAST hit, 70.42 % have an ortholog hit ratio (OHR) ≥0.5 and 50.49 % have an OHR of ≥0.8
Fig. 2
Fig. 2
Transcripts that show significant differential expression in the O. nubilalis midgut. Results shown for transcriptional response to Cry1F protoxin in the susceptible strain (S), transcriptional response to Cry1F protoxin exposure in the resistant strain (R), and Constitutive differences between the Cry1F resistant and susceptible strains. Cutoffs for estimated differential expression set at FDR adjusted p-values ≤ 0.05
Fig. 3
Fig. 3
Transcripts differentially expressed between the Cry1F resistant and susceptible O. nubilalis strains. The x-axis indicates the total numbers of genes differentially expressed in each category. Only the constitutive differences between the Cry1F resistant and susceptible strains are shown in the figure
Fig. 4
Fig. 4
Different gene expression comparisons in this study. 1: Cry1F toxin induced transcriptional differences in the susceptible strain, 2: Cry1F toxin induced transcriptional differences in the resistant strain, 3: Constitutive transcriptional differences between the susceptible and resistant strain, 4: Strain and Cry1F toxin interactions. S and Cry1F-S represents the susceptible and Cry1F treated susceptible strain respectively. R and Cry1F-R represents the resistant and Cry1F treated resistant strain respectively
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References

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