Transcriptome analysis and histopathological observations of Geloina erosa gills upon Cr(VI) exposure

The heavy metal contamination like Cr(VI) has been increased by human activities and that threats the ecosystem health of mangrove areas. Bioindicator is an emerging tool in the environmental contamination assessment. The objective of this study was to investigate the Geloina erosa response mechanisms and sensitivities of several biomarkers in the Cr(VI) exposure and identify the G. erosa capability of being used as heavy metals bioindicator. In this study, G. erosa was exposed to 100 μmol·L^-1 Cr(VI) for 48 h. After transcriptome sequencing, a total of 134,817 unigenes were obtained, including 12,555 up-regulated and 18,829 down-regulated differentially expressed genes and were validated through quantitative real-time PCR. In addition, a total of 12,185 SSRs and 1,428,214 candidate SNPs were identified from all the G. erosa transcriptome libraries. Histopathology of the gill indicated the Cr(VI) exposure induced damage of the organ leading to its immunization, detoxification or apoptosis reactions. Among eight genes of the selected biomarkers, Calm, HSP70, CYP450, ATG5, TLR2, MYD88 and CASP8 were up-regulated, while TLR4 was down-regulated in response to the Cr(VI) exposure.