Transcriptomic analysis reveals the key immune-related signalling pathways of Sebastiscus marmoratus in response to infection with the parasitic ciliate Cryptocaryon irritans

Fei Yin,Dong Qian

doi:10.1186/s13071-017-2508-7

Abstract

BackgroundFalse kelpfish (Sebastiscus marmoratus) is one of the target species in artificial breeding in China, and is susceptible to infection by Cryptocaryon irritans, which is an obligate parasitic ciliate that lives in the epithelium of the fish gills, skin and fins. Here, we sought to understand the mechanisms of molecular immunity of S. marmoratus against C. irritans infection.MethodsWe carried out an extensive analysis of the transcriptome of S. marmoratus immune-related tissues. A paired-end library was constructed from the cDNA synthesized using a Genomic Sample Prep Kit. Five normalized cDNA libraries were constructed using RNA from the control group and the four groups of C. irritans-infected fish. The libraries were sequenced on an Illumina Mi-Seq platform, and functional annotation of the transcriptome was performed using bioinformatics software.ResultsThe data produced a total of 149,983,397 clean reads from five cDNA libraries constructed from S. marmoratus immune-related tissues. A total of 33,291 unigenes were assembled with an average length of 1768 bp. In eggNOG (Evolutionary Genealogy of Genes: non-supervised orthologous groups) categories, 333 unigenes (0.94%) were assigned to defense mechanisms. In the immune system process sub-categories of gene ontology (GO) enrichment analysis, with the passage of time post-infection, the number of differentially expressed genes (DEGs) was reduced from 24 h to 48 h but then increased from 72 h to 96 h. Specifically, the immune-related differentially expressed genes (IRDEGs), which belong to the KEGG (Kyoto encyclopedia of genes and genomes) pathways, such as the complement and coagulation cascades, chemokine signalling pathways and toll-like receptor signalling pathways were mainly observed at 24 h post-infection.ConclusionsInfection with C. irritans resulted in a large number of DEGs in the immune-related tissues of S. marmoratus. The rapid and significant response of the S. marmoratus immune signalling pathways following C. irritans infection may be associated with their involvement in the immune process.

Highlights

False kelpfish (Sebastiscus marmoratus) is one of the target species in artificial breeding in China, and is susceptible to infection by Cryptocaryon irritans, which is an obligate parasitic ciliate that lives in the epithelium of the fish gills, skin and fins
Previous research has indicated that C. irritans infection results in elevated of serum cortisol, glucose contents, accelerate respiratory rate, and reduced food intake in S. marmoratus [1, 3]
Infection with C. irritans caused a large number of differentially expressed genes (DEGs) in the IR-tissues of S. marmoratus

Summary

Introduction

False kelpfish (Sebastiscus marmoratus) is one of the target species in artificial breeding in China, and is susceptible to infection by Cryptocaryon irritans, which is an obligate parasitic ciliate that lives in the epithelium of the fish gills, skin and fins. As a common target species for the fishing industry, the false kelpfish (Sebastiscus marmoratus) is mainly distributed in the Western North Pacific. The small size and ease of feeding have made S. marmoratus a target species in artificial breeding programs in China. Available data indicate that S. marmoratus is a susceptible host to Cryptocaryon irritans [1]. For these reasons, this species of fish is a good candidate in which to study the aetiology and pathogenesis of C. irritans. To date, the patterns of immunological responses in infected S. marmoratus has not been thoroughly studied

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Results

Conclusion