Approved Abstracts

Gene expression study alerted to possible impairment in Daphnia magna individuals as a consequence of exposure to sublethal concentrations of prochloraz

Author(s): Salesa B; Torres-Gavilá FJ; Ferrando-Rodrigo MD; Sancho-Aguilar E;
Presenter: Beatriz Salesa Landete

Aquatic animals could be affected at very low concentrations of toxicants in their medium, the relationship between contamination levels and ecosystems safety is a stone question for aquatic toxicology studies. Studies about gene expression in exposed animals could be an early tool to alert about some genetic biomarkers disfunctions and advertise of a possible damage before individual or population level were affected.
In the present study, Daphnia magna individuals were exposed for 21 days to 87, 130, 170, 230 and 380 μg/L of prochloraz (sublethal concentrations based on the prochloraz CE50- 48 h).
After fungicide exposure, the expression of genes related to lipid metabolism (fabd), oxidative stress (cat and gst), heat shock proteins synthesis (hsp70 and hsp90), hemoglobin synthesis (hgb1 and hgb2), metalotioneins synthesis (mt-a, mt-b and mt-c), and vitelogenines synthesis (vgt1 y vgt2), plus reference gene (GAPDH) were analyzed.
At 21st day, 6 individuals from each test concentration, were collected for RNA extraction, synthesis of cDNA and the real-time qPCR were performed.
Results showed that some gene expression in D. magna was altered as a consequence of the individual exposure to the fungicide. The genes fabd, vtg1 and vtg2, cat and gst resulted unaltered by the exposure of the daphnids to different fungicide concentrations. However, daphnid exposure to 380 μg/L of prochloraz resulted in an overexpression (p<0.05) of hsp70 gene which indicated an alteration of the normal protein synthesis and its integrity maintenance. On the other hand, mt-b gene resulted significantly underexpressed (p<0.05) in daphnids exposed to the lowest fungicide concentrations (87, 130 and 170 μg/L, respectively). Although metalotioneins had been usually related to metal detoxification, also it can be altered by the presence of other kind of pollutants including pesticides.
In addition, hgb1 and hgb2 genes which are related with the hemoglobin synthesis were significantly overexpressed (p<0.05). Results showed that hgb1 gene was overexpressed more than 200 times in daphnids exposed for 21 days to 170, 230 and 380 μg/L compared to control values. Similar results were found on hgb2 gene which was also overexpressed in daphnids exposed to all tested fungicide concentrations (p<0.05). At the same time, the disfunction of both hemoglobin genes were correlated with an increase of daphnid pigmentation during the experiment.
Alteration in the hemoglobin gene expression is historically associated with hypoxic or anoxic situations. However, many authors advocate by an association of these gene expression changes with the presence of contaminants in the medium, in fact they could be used as a good indicator of early contamination at low concentrations of toxicants.

Keywords: Gene expression; Early biomarkers; Daphnia magna




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