Gene Expressions of the Dhb, Vtg, Arnt, CYP4, CYP314 in Daphnia magna Induced by Toxicity of Glyphosate and Methidathion Pesticides

Abstract

Pesticides, the chemicals used commonly in agriculture to control pests, pathogens and weeds, have been contributing to the serious contamination of the aquatic environment through spray drift, volatilization, drainage and leaching (Cerejeira et al., 2003; Pereira et al., 2009). Among various pesticides, methidathion is a highly toxic insecticide used to control a wide spectrum of agricultural insect and mite pests. In the other hand, glyphosate, the active ingredient in many commercial weed-killing formulation (e.g., Roundup), is widely used in agricultural, silvicultural and urban environment (Borggaard, K.O., and Gimsing, L.A., 2008). The results are an increasing detection of these pesticides in the environment, especially in aquatic system may have some ecotoxicological impacts on non-target aquatic organisms (Tsui et al., 2003; Vorkamp et al., 2002). D. magna, a freshwater crustacean, has been used extensively to evaluate the toxic effects of chemical on aquatic system (EPA, 2002) because of their high sensitivity to a wide range of chemicals, a short lifecycle, and ease of manipulation in the laboratory. In addition, the daphnia are ubiquitous and play a key role in aquatic food web (Soetaert et al., 2006). Conventionally, the toxicity assays (e.g., acute or chronic toxicity tests) have widely been used to evaluate the aquatic toxicity as well as the adverse impacts of the toxic chemicals on aquatic organisms based on the phynotic endpoints such as the survival, growth, and reproduction (Colleen et al., 2005; Heckmanna et al., 2007). These body responses result from some molecular responses (e.g., gene expression) in organisms that expose to a toxic environment. Therefore, changing in gene expression in the organisms should happen first, and be a more sensitive indicator to the toxic chemicals than the body responses (Jo et al., 2008; Le et al., 2010; Le et al., 2011). Notably, when an organism is exposed to a toxic environment, the metabolic activity in the organism will change to overcome the adverse effects (Ankley and Villeneuve, 2006). Certain genes, possessing the particular functions, express differently in organisms that are exposed to toxicants. For instance, hemoglobins (Dhb), the protein are distributed widely in all organisms, are composed of multiple two-domain chains with a relatively normal oxygen binding activity when found in the hemolymph of D. magna (Tokishita et al., 1997; Anderson et al., 2008). Vitellogenin (Vtg) is a major lipoprotein in many oviparous animals and has