Transcriptome analysis of genes expressed in the earthworm Eisenia fetida in response to cadmium exposure

Eisenia fetida earthworm is an ecotoxicologically important test species to monitor various pollutants. However, there is a little knowledge about the effects of cadmium (Cd) on earthworms at the transcriptional level. Firstly, we exposed E. fetida to soils supplemented with different concentrations (10, 30, 60 mg/kg soil) of Cd. Moreover, we depicted the characterization of gene expressions with E. fetida using high-throughput profiling of gene expression. In addition, a comparison of the gene expression profiles between each Cd treatment group and the control group suggested that differential expressional genes (DEGs) mainly enriched in enzyme activity, metabolism, oxidative stress, regeneration and apoptosis pathways. 8 DEGs from these pathways had been selected randomly to confirm the data of RNA-seq. Among these DEGs, six genes (metallothionein-2, phytochelatin synthase 1a, CuZn superoxide dismutase, sex determining region Y-box 2, sex determining region Y-box 4b, TP53-regulated inhibitor of apoptosis 1-like) up-regulated and 2 genes (beta-1,4-endoglucanase, apoptosis-stimulating of p53 protein 2-like) down-regulated in response to Cd exposure. The alteration of them indicated that earthworms could reduce the toxicity and bioavailability of Cd in polluted soil ecosystems through different pathways. This work lays an important foundation for linking earthworm transcriptional level with the ecological risk of Cd in soil ecosystem.