LAUSR

The Pearl River Estuary (PRE) is the largest estuary in southern China and under high metal stress. In the present study, we employed an integrated method of transcriptomics and proteomics to investigate the ecotoxicological effects of trace metals on the Hong Kong oyster Crassostrea hongkongensis. Three oyster populations with distinct spatial distributions of metals were sampled, including the Control (Station QA, the lowest metal levels), the High Cd (Station JZ, the highest Cd), and the High Zn-Cu-Cr-Ni (Station LFS, with the highest levels of zinc, copper, chromium, and nickel). Dominant metals in oysters were differentiated by principal component analysis (PCA), and theirgene and protein profiles were studied using RNA-seq and iTRAQ techniques. Of the 2250 proteins identified at both protein and RNA levels, 70 proteins exhibited differential expressions in response to metal stress in oysters from the two contaminated stations. There were 8 proteins altered at both stations, with the potential effects on mitochondria and endoplasmic reticulum by Ag. The genotoxicity, including impaired DNA replication and transcription, was specifically observed in the High Cd oysters with the dominating influence of Cd. The structural components (cytoskeleton and chromosome-associated proteins) were impaired by the over-accumulated Cu, Zn, Cr, and Ni at Station LFS. However, enhanced tRNA biogenesis and exosome activity might help the oysters to alleviate the toxicities resulting from their exposure to these metals. Our study provided comprehensive information on the molecular changes in oysters at both protein and RNA levels in responding to multi-levels of trace metal stress.