Molecular impact of propiconazole on Daphnia magna using a reproduction-related cDNA array.

We have developed a first version cDNA microarray of the cladoceran Daphnia magna. Through Suppression Subtractive Hybridisation PCR (SSH-PCR) 855 life stage-specific cDNAs were collected and used to document the toxicological mode of action of the pesticide propiconazole. DNA sequencing analysis revealed gene fragments related to important functional classes such as embryo development, energy metabolism, molting and cell cycle. Major changes in transcription were observed in organisms exposed for 4 and 8 days to 1 microg/mL. After 4 days a 3-fold down-regulation of the gene encoding the yolk protein, vitellogenin, was observed indicating impaired oocyte maturation. Moreover, genes such as a larval-specific gene and chaperonin were repressed, whereas the heat shock 90 protein and ATP synthase were induced. Organismal effects clearly confirmed the major molecular findings: at the highest concentration (1 microg/mL) adult growth was significantly (p < 0.05) impaired and increased developmental effects in the offspring could be noted. We have demonstrated the potential of microarray analysis in toxicity screening with D. magna. The use of vitellogenin mRNA as a rapid biomarker of reproductive effects in chronic toxicity studies with cladocerans is suggested.