Abstract:
Background: Anopheles gambiae larvae traditionally thrive in non-polluted
environments. We previously documented the presence of the larvae in heavy
metal polluted urban aquatic environments and the associated biological cost.
The goal of this study was to unravel the molecular dynamics involved in the
adaptation of the mosquitoes to the heavy metals.
Methods: Total RNA was extracted from third instar larvae of both cadmium
treated populations and untreated control populations. The RNA concentrations
were normalized and complementary DNAs were prepared. Then annealing
control primer (ACP) technology was applied to establish transcriptional
responses in An. gambiae larvae following several generational (n=90) chronic
exposures to cadmium. Differentially expressed genes were determined by
their differential banding patterns on an agarose gel. Gel extraction and
purification was then carried out on the DEGs and these were later cloned and
sequenced to establish the specific transcripts.
Results: We identified 14 differentially expressed transcripts in response to the
cadmium exposure in the larvae. Most (11) of the transcripts were up-regulated
in response to the cadmium exposure and were putatively functionally
associated with metabolism, transport and protein synthesis processes. The
transcripts included ATP-binding cassette transporter, eupolytin, ribosomal
RNA, translation initiation factor, THO complex, lysosomal alpha-mannosidase,
sodium-independent sulfate anion transporter and myotubularin related protein
2. The down-regulated transcripts were functionally associated with signal
transduction and proteolytic activity and included Protein G12, adenylate
cyclase and endoplasmic reticulum metallopeptidase.
Conclusions: Our findings shed light on pathways functionally associated with
the adaptation to heavy metals that can be targeted in integrated vector control
programs, and potential An. gambiae larvae biomarkers for assessment of
environmental stress or contamination.
