Effects of pentachlorophenol on Drosophila melanogaster transcriptome

ABSTRACT Among largely used synthetic molecules, the chlorinated ones have been extensively applied as pesticides. Pentachlorophenol (PCP) has been one of the most extensively used biocides in the United States and in Europe. In the last decades its use has been restricted in several countries worldwide, due to its toxicity to wildlife, the long persistence in the environment and bioaccumulation in fat tissues. Public increasing interest in an ecologically safe environment remediation, together with the awareness that biotechnology has high potential to satisfy this need, is leading towards different approaches for bioremediation. PCP-degrading bacteria and fungi catabolizing PCP are known, but looking for diverse and not yet characterized efficient degradation pathways can result in improving the available tools. Insects represent a potential and relatively unexplored source of metabolic mechanisms for detoxification of a wide variety of both natural and synthetic compounds due to their genetic plasticity. Drosophila melanogaster was used as a model insect, and a set of differentially expressed genes associated with PCP response in the fruitfly was identified on the basis of genome-wide microarray analysis. Two PCP doses were tested, 20 and 2000 ppm, the latter causing a higher level of response, in terms of significantly differentially expressed genes. The enrichment analysis of the overexpressed 2000 ppm PCP treatment highlighted a strong response in the biogenic amine metabolic pathways, with the induction of genes potentially involved in degradation pathways, such as the tyrosine monooxygenase. The main detoxifying gene families were involved in the PCP response, with overexpression of five CYPs and one GST. Moreover two ABC transporter genes were found to be induced. Two 2000 ppm PCP resistant Drosophila strains were selected, in order to obtain a deeper knowledge of the effects of PCP on Drosophila, and to elucidate PCP metabolic pathaways. For this purpose HPLC analyses were carried out on PCP supplied diet on which resistant larvae fed on, evidencing a reduction of PCP as a consequence of feeding activity.