Dose‐dependent effects of metals on gene expression in the sydney rock oyster, Saccostrea glomerata

Abstract

In the current study, we tested the effects of common environmental contaminants (the metals zinc and lead) on gene expression in Sydney rock oysters (Saccrostrea glomerata). Oysters were exposed to a range of metal concentrations under controlled laboratory conditions. The expression of 14 putative stress response genes was then measured using quantitative, real-time (q) PCR. The expression of all 14 genes was significantly affected (p < 0.05 vs. nonexposed controls) by at least one of the metals, and by at least one dose of metal. For 5 of the 14 target genes (actin, calmodulin, superoxide dismutase, topoisomerase I, and tubulin) the alteration of expression relative to controls was highest at intermediate (rather than high) doses of metals. Such responses may reflect adaptive (acclimation) reactions in gene expression at low to intermediate doses of contaminants, followed by a decline in expression resulting from exposure at higher doses. The data are discussed in terms of the intracellular pathways affected by metal contamination, and the relevance of such gene expression data to environmental biomonitoring.

The biology of environmental stress: molecular biomarkers in Sydney rock oysters (Saccostrea glomerata)

“…Once the reference database of cDNA sequences had been assembled, we began a series of laboratory-based experiments in which different groups of oysters were exposed separately to four metals (cadmium, copper, lead and zinc) that are commonly associated with anthropogenic pollution in Sydney Harbour and other coastal estuaries on Australia's eastern seaboard. [65][66][67][68][69] Oysters were exposed to different concentrations of each metal (5 mg l À1 to 100 mg l À1 ) for four days before their gills or hemocytes (blood cells) were collected for analysis. The doses of metals used are biologically relevant, representing low to relatively high concentrations found in contaminated environments.…”

“…The doses of metals used are biologically relevant, representing low to relatively high concentrations found in contaminated environments. 69 Initially, we tested the transcriptional expression of a selected set of seven genes (superoxide dismutase, ferritin, colin, defensin, HSP70, HSP90 and metallothionein) in gill samples from oysters exposed to the 100 mg l À1 doses. 65 These target genes were chosen from our NGS database because changes in their transcript abundance had previously been reported in other bivalves responding to environmental contamination.…”

“…2). 69 This expanded set of target genes included several that were identied by proteomic analyses (described below 68 ) and fell into a range of intracellular functional pathways. The expression of all 14 genes was signicantly affected (p < 0.05 vs. non-exposed controls) by at least one of the metals tested, and by at least one dose of that metal.…”

“…This meant that some key proteins were associated with responsiveness in most, if not all of our studies. [65][66][67][68][69]86,88,92 We were able to assign identities to 317 proteins in our six studies of Sydney rock oysters exposed to environmental stress. Molecular chaperones (heat shock proteins, HSPs) were the most commonly identied, representing 32 of the 317 identications.…”

Antioxidant and detoxification responses of oysters Crassostrea hongkongensis in a multimetal‐contaminated estuary

“…No significant correlation between metal concentration of oyster tissues and SOD activity was observed in the present study, which may be because of possible antagonistic effects of some trace metals. Expression of SOD in hemolymph of Sydney rock oyster ( Saccostrea glomerata ) was inhibited after Cd exposure but was significantly up‐regulated after Zn exposure . A change in SOD expression level may lead to a change in SOD activity.…”