Comparative de novo transcriptomics reveal the effect of lead on Leech in aquaculture environment

Whitmania pigra Whitman is a non-bloodsucking leech, which is included in the Pharmacopoeia of the People's Republic of China. As a traditional Chinese medicine, its main function is to remove the blood stasis. In the process of breeding, Whitmania pigra Whitman is easily affected by the pollution of the heavy metal lead. This study simulated the pond culture environment in the aquarium with the soil in the bottom. The soil lead contamination was caused by adding lead nitrate to the soil. The blank leech group and lead contaminated leech group were obtained after 50 days of culturing in the aquariums. Denovo assembly and analysis were performed to reveal the changes of gene expression in Whitmania pigra Whitman after lead contamination. The sequencing results showed that each sample had more than 45 million Raw Reads and the percentage of Clean reads was more than 96%. There were altogether 120,684 transcripts which average length is 1590.42 bp. 34,612 unigenes were annotated based on the sequence homology. In result, a total of 1110 differentially expressed genes were obtained, including 694 up-regulated genes and 416 down-regulated genes. The GO enrichment analysis of differentially expressed genes was significantly enriched to 85 GO entries. In the other hand, the KEGG enrichment analysis of differentially expressed genes was significantly enriched to 5 pathways, among which arachidonic acid metabolism and lysosomes were important pathways. In conclusion, the results of this study can provide data support for future studies on the quality of leech and provide a reference for the effects of heavy metal lead accumulation in the culture environment on aquatic organisms.