The survival of any organism exposed to an environmental stress depends on its ability to elicit a stress response. This response is characterized by the induction or repression of multiple stress-response genes. We are examining the effects of cadmium exposure on C. elegans to characterize the mechanism(s) responsible for the transcriptional regulation of the stress response. The RT-PCR differential display protocol was used to identify mRNAs whose steady-state levels of expression are affected following ~8 or 24h cadmium-treatments. We identified 14 cDNAs that have altered levels of expression in cadmium-treated C elegans, compared to non-treated control worms. DNA sequences of 8 clones were 100% identical to C. elegans
mtl-1 cDNA, confirming the efficacy of this method in identifying mRNAs whose level of expression change in response to cadmium. BLAST analysis indicates that clones designated VL19 and VL21 are homologous pyruvate carboxylase (>70% identity) and identical to C. elegans
hsp-70 precursor, respectively. Northern blot and quantitative RT-PCR analyses confirmed that VL19 and VL21 mRNAs increased in response to cadmium-treatment. BLAST analysis shows that the translated amino acid sequences of the other differentially displayed cDNAs are novel and are not significantly homologous to proteins in the database. The effect of cadmium-treatment on the expression of C. elegans homologs of the stress-response genes, superoxide dismutase, catalase, ubiquitin-like protein, ubiquitin conjugating enzyme and heat shock proteins, was determined by Northern blot analysis. Cadmium-treatment caused an increase in the levels of catalase and ubiquitin-like protein mRNAs, and did not affect SOD mRNA levels. The effect of cadmium-treatment on the levels of other stress-inducible mRNAs is currently under investigation.