Larval midgut modifications associated with Bti resistance in the yellow fever mosquito using proteomic and transcriptomic approaches.
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.
Laboratoire d'Ecologie Alpine, LECA-UMR 5553, Université de Grenoble 1, BP 53, 38041 Grenoble cedex 09, France. guillaume.tetreau@gmail.com
Guillaume
G
Tetreau
Krishnareddy
K
Bayyareddy
Christopher M
CM
Jones
Renaud
R
Stalinski
Muhammad A
MA
Riaz
Margot
M
Paris
Jean-Philippe
JP
David
Michael J
MJ
Adang
Laurence
L
Després
D000469:Alkaline Phosphatase / Q000235:genetics / Q000378:metabolism; D000626:Aminopeptidases / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001413:Bacillus thuringiensis / Q000378:metabolism* / Q000472:pathogenicity*; D009033:Culicidae / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology*; D007814:Larva / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology*; D020411:Oligonucleotide Array Sequence Analysis; D040901:Proteomics / Q000379:methods*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D059467:Transcriptome / Q000235:genetics*; D025262:Vacuolar Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism; D015004:Yellow Fever / Q000635:transmission*
D000469:Alkaline Phosphatase; D000626:Aminopeptidases; D025262:Vacuolar Proton-Translocating ATPases