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Abstract
We developed a high-resolution expression microarray based on 2456 unique transcripts
from a cDNA library of the aquatic midge (Chironomus tentans). By using the microarray,
we detected that 146, 434 and 243 genes were differentially expressed after C. tentans
larvae were exposed to chlorpyrifos (organophosphate insecticide) at 0.1 and 0.5 μg/L,
and atrazine (triazine herbicide) at 1000 μg/L, respectively, for 48 h. The number
of differentially expressed genes in the larvae exposed to chlorpyrifos at 0.5 μg/L
was three times of that in the larvae exposed to chlorpyrifos at 0.1 μg/L. Among the
differentially expressed genes in response to chlorpyrifos exposures, 76 genes showed
significant Blast hits, and among them 42 were in common between the chlorpyrifos
and atrazine exposures. In 19 differentially expressed xenobiotic detoxification genes,
16 were significantly up-regulated in the larvae exposed to chlorpyrifos and/or atrazine.
Two cytochrome P450 genes (CtCYP6EV1 and CtCYP4DG2) were specifically up-regulated
by chlorpyrifos, whereas three cytochrome P450 genes (CtCYP4DG1, CtCYP6EX3 and CtCYP6EV3)
were specifically up-regulated by atrazine. Our results showed that chlorpyrifos exposures
even at low concentrations can lead to significant changes in gene expression. The
significant transcriptional responses are likely attributed to larval intoxication
by the insecticide. These results not only support our previous studies in which candidate
gene approaches were used, but also can potentially help develop specific molecular
markers for monitoring pesticide exposures in non-target organisms in aquatic systems.