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Highlights: [•] Glutathione biosynthesis genes from Chironomus riparius were characterized. [•] Transcriptional regulation of GSH biosynthesis genes was studied after exposure to Cd and NP. [•] Modulation in the expression of GSH biosynthesis genes was observed after exposure to Cd and NP. [•] Potentially used as biomarkers of Cd and NP stress in aquatic environment. [ABSTRACT FROM AUTHOR]

Abstract: Superoxide dismutase (SOD, EC 1.15.1.1) is an enzyme involved in the scavenging of reactive oxygen species (ROS) into molecular oxygen and hydrogen peroxide. In this study, a copper–zinc superoxide dismutase (Cu–ZnSOD) gene and a manganese superoxide dismutase (MnSOD) gene in aquatic midge, Chironomus riparius (CrSODs) was identified using an Expressed Sequence Tag (EST) database generated by 454 pyrosequencing. A multiple sequence alignment of C. riparius sequences revealed high homology with other insect sequences in terms of the amino acid level. Phylogenetic analysis of the CrSODs revealed that they were grouped with SODs of other organisms, such as Polypedilum vanderplanki, Drosophila melanogaster, Aedes aegypti, Anopheles gambiae, Culex quinquefasciatus and Bombyx mori. Expression of the corresponding CrSODs was analyzed during different developmental stages and following exposure to various environmental contaminants with different mode of actions i.e., paraquat, cadmium, benzo[a]pyrene, and chloropyrifos. CrSOD gene expression was significantly up or down regulated in response to exposure to the chemicals tested. The overall results suggested that SOD gene expression provided a platform for the understanding of oxidative stress responses caused by exposure to various environmental contaminants, and the SOD genes could be used as biomarkers for environmental disturbances such as oxidative stress initiated by xenobiotics. [Copyright &y& Elsevier]

Abstract: In this study, we report the identification and characterization of 13 cytosolic GST genes in Chironomus riparius from Expressed Sequence Tags (ESTs) database generated using pyrosequencing. Comparative and phylogenetic analyses were undertaken with Drosophila melanogaster and Anopheles gambiae GSTs and 3 Delta, 4 Sigma, 1 each in Omega, Epsilon, Theta, Zeta and 2 unclassified classes of GSTs were identified and characterized. The relative mRNA expression levels of all of the C. riparius GSTs (CrGSTs) genes under different developmental stages were varied with low expression in the larval stage. The antioxidant role of CrGSTs was studied by exposing fourth instar larvae to a known oxidative stress inducer Paraquat and the relative mRNA expression to different concentrations of cadmium (Cd) and silver nanoparticles (AgNPs) for various time intervals were also studied. All the CrGSTs showed up- or down regulation to varying levels based upon the concentration, and duration of exposure. The highest mRNA expression was noticed in Delta3, Sigma4 and Epsilon1 GST class in all treatments. These results show the role of CrGST genes in defense against oxidative stress and its potential as a biomarker to Cd and AgNPs exposure. [Copyright &y& Elsevier]