The microRNA Targeting Cu/Zn-SOD Increases the Susceptibility To WSSV Under Ammonia Stress in Pacific White Shrimp Litopenaeus vannamei.

The high concentration of ammonia from deteriorated aquaculture environments and intensive culture system increases the susceptibility to white spot syndrome virus (WSSV) and causes high mortality in Pacific white shrimp Litopenaeus vannamei. However, its molecular mechanism remains to be elucidated. In the present study, small RNA sequencing was performed for understanding the molecular mechanism of acute ammonia toxicity increasing susceptibility to WSSV in Pacific white shrimp with the individuals under normal conditions (LC group), ammonia stress (LA group), WSSV infection (LV group), and WSSV infection with ammonia stress (LAV group). Compared with other groups, more significantly upregulated differentially expressed miRNAs (DEMs) were identified in the LAV group, which targeted to the immune-, energy metabolism-, and ROS scavenging-related genes. The KEGG enrichment analysis showed that the target genes of the DEMs in LA and LAV groups (both with ammonia stress) were specially involved in viral carcinogenesis, and those in LAV group were also specially involved in hippo signaling pathway and chemokine signaling pathway. The copper zinc superoxide dismutase (Cu/Zn-SOD) was predicted as the target gene of the specific DEMs of novel_59 and novel_71 in the LAV group. The mRNA expression and enzyme activity of Cu/Zn-SOD was significantly lower in the LAV group than other groups, but the ROS production rate was the highest in the LAV. This study provides new insights for understanding the molecular mechanism of high WSSV-infection under ammonia toxicity in shrimps from the post-transcriptional perspective.