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Open Access Highly Accessed Research article

Larval midgut modifications associated with Bti resistance in the yellow fever mosquito using proteomic and transcriptomic approaches

Guillaume Tetreau1*, Krishnareddy Bayyareddy2, Christopher M Jones3, Renaud Stalinski1, Muhammad A Riaz1, Margot Paris1, Jean-Philippe David1, Michael J Adang24 and Laurence Després1

Author Affiliations

1 Laboratoire d’Ecologie Alpine, LECA-UMR 5553, Université de Grenoble 1, BP 53, 38041, Grenoble cedex 09, France

2 Department of Entomology, University of Georgia, Athens, GA, 30602-2603, USA

3 Vector Group, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK

4 Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602-2603, USA

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BMC Genomics 2012, 13:248  doi:10.1186/1471-2164-13-248

Published: 15 June 2012

Abstract

Background

Bacillus thuringiensis var. israelensis (Bti) is a natural larval mosquito pathogen producing pore-forming toxins targeting the midgut of Diptera larvae. It is used worldwide for mosquito control. Resistance mechanisms of an Aedes aegypti laboratory strain selected for 30 generations with field-collected leaf litter containing Bti toxins were investigated in larval midguts at two levels: 1. gene transcription using DNA microarray and RT-qPCR and 2. differential expression of brush border membrane proteins using DIGE (Differential In Gel Electrophoresis).

Results

Several Bti Cry toxin receptors including alkaline phosphatases and N-aminopeptidases and toxin-binding V-ATPases exhibited altered expression levels in the resistant strain. The under-expression of putative Bti-receptors is consistent with Bt-resistance mechanisms previously described in Lepidoptera. Four soluble metalloproteinases were found under-transcribed together with a drastic decrease of metalloproteinases activity in the resistant strain, suggesting a role in resistance by decreasing the amount of activated Cry toxins in the larval midgut.

Conclusions

By combining transcriptomic and proteomic approaches, we detected expression changes at nearly each step of the ingestion-to-infection process, providing a short list of genes and proteins potentially involved in Bti-resistance whose implication needs to be validated. Collectively, these results open the way to further functional analyses to better characterize Bti-resistance mechanisms in mosquitoes.

Keywords:
Aedes aegypti; Bacillus thuringiensis israelensis; DIGE; Microarray; RT-qPCR; Resistance; Transcriptomics; Proteomics; Midgut; Mosquito; Candidate genes