Mucus piRNAs profiles of Vibrio harveyi-infected Cynoglossus semilaevis: A hint for fish disease monitoring

The half-smooth tongue sole, Cynoglossus semilaevis, is an important cultured flatfish species. Vibrio harveyi is a common pathogen to this fish, which may result in great economic loss to C. semilaevis culture industry. piRNAs, a non-coding RNAs with 26-32 nt, have been regarded as promising biomarkers for cancer diagnosis and fish diseases. Here, we extracted the RNA from mucus of C. semilaevis and constructed the differential expression profiles of piRNAs between the sick fish (MS) and healthy fish (MC). We identified 45,696 differentially expressed piRNAs including 22,735 up-regulated piRNAs and 22,961 down-regulated piRNAs in MS group compared with MC group. The GO enrichment and KEGG pathway enrichment analyses of the differential piRNAs were carried out. The result showed immunity-related target genes mainly involved in immune system process, response to stimulus, cell killing, immune system, infectious diseases and cell growth and death. The 10 most differentially expressed piRNAs were chosen to perform the qRT-PCR, while only seven piRNAs were consistent with the sequence result. Compared with MC group, the expression levels of piR-mmu-72173>piR-rno-62831>piR-xtr-704880, piR-dme-15546979, piR-mmu-49941660, piR-mmu-29283297 and piR-mmu-1758399 were significantly lower, and piR-gga-10574 and piR-gga-134812 were significantly higher in MS group. These piRNAs may be potential biomarkers during the V. harveyi infection of C. semilaevis. This study could provide a new method to identify the infection status of C. semilaevis and understand better about the innate and adaptive immune system in C. semilaevis during bacterial infection.

Automated summary

The study identified differentially expressed piRNAs in the mucus of sick and healthy half-smooth tongue sole, with immunity-related target genes being the main focus. qRT-PCR results revealed significant differences in expression levels of specific piRNAs, which could serve as potential biomarkers during Vibrio harveyi infection in the fish.