Hepatopancreas transcriptome alterations in red claw crayfish (Cherax quadricarinatus) under microcystin-LR (MC-LR) stress

Red claw crayfish (Cherax quadricarinatus) is a valuable aquatic species with fast growth, big size, delicious meat, and strong resistance to diseases worldwide. Microcystin-LR (MC-LR) is the most common and potently toxic and is known to infect aquatic animals. The present study was performed at the transcriptome level to investigate the mechanism of C. quadricarinatus in responses to MC-LR by RNA sequencing (RNA-seq) analysis. A total of 57,153,501, 51,955,723, and 56,316,927 clean reads were retrieved from the three libraries of C. quadricarinatus (0 h, 6 h, and 48 h). A total of 37,616 unigenes were identified and compared with NR, Swiss-Prot, Pfam, COG, GO, and KEGG databases. A total of 4980 and 4585 differentially expressed genes (DEGs) were obtained at 6 h and 48 h compared with control (0 h), respectively. Most of these DEGs were up-regulated in 6 h, but most were down-regulated in 48 h, indicating that gene expression levels were inhibited by MC-LR in 48 h. Based on the GO and KEGG pathways analyses of DEGs, we obtained various pathways related to apoptosis, immunity, and detoxification. A total of 234 DEGs were related to the immune system, including 19 immune metabolic pathways, such as the Toll-like receptor signaling pathway, Toll and Imd signaling pathway, interleukin-17 (IL-17) signaling pathway, etc. Besides, detoxification-associated and apoptosis-associated pathways were also identified, including drug metabolism-cytochrome P450 and glutathione metabolism, apoptosis and p53 signaling pathway, etc. Twelve DGEs involved in immune response and MC-LR detoxification were discovered and validated by quantitative real-time polymerase chain reaction (qRT-PCR). The results indicated that the C. quadricarinatus might counteract the toxicity of MC-LR at the transcriptomic level by increasing expression levels of immune- and detoxification-related genes. In summary, this study first reported the response mechanism of the C. quadricarinatus with injected MC-LR at the transcriptional level. The identification of differential expression genes and pathways can help us to understand further the response mechanism of C. quadricarinatus under MC-LR stress.