Abstract
The hybrid sturgeon (Huso dauricus × Acipenser schrenckii) is an economically important species in China. With the increasing aquaculture of hybrid sturgeon, the bacterial diseases are a great concern of the industry. In this study, de novo sequencing was used to compare the difference in transcriptome in spleen of the infected and mock infected sturgeon with Aeromonas hydrophila. Among 187,244 unigenes obtained, 87,887 unigenes were annotated and 1,147 unigenes were associated with immune responses genes. Comparative expression analysis indicated that 2,723 differently expressed genes between the infected and mock-infected group were identified, including 1,420 up-regulated and 1,303 down-regulated genes. 283 differently expressed anti-bacterial immune related genes were scrutinized, including 168 up-regulated and 115 down-regulated genes. Ten of the differently expressed genes were further validated by qRT-PCR. In this study, toll like receptors (TLRs) pathway, NF-kappa B pathway, class A scavenger receptor pathway, phagocytosis pathway, mannose receptor pathway and complement pathway were shown to be up-regulated in Aeromonas hydrophila infected hybrid sturgeon. Additionally, 65,040 potential SSRs and 2,133,505 candidate SNPs were identified from the hybrid sturgeon spleen transcriptome. This study could provide an insight of host immune genes associated with bacterial infection in hybrid sturgeon.
Highlights
Sturgeon is an important fish species farmed worldwide, which has significant economic value as an animal protein source, including caviar and meat[1,2]
Transcriptome sequencing and assembly. 137,779,578 and 138,474,832 raw reads from the spleen of Aeromonas hydrophila infected and mock infected hybrid sturgeons, respectively, were obtained using Illumina Hiseq. 2000 deep sequencing analysis
The length distribution showed that 62.63% of the unigenes were clustered in a group with 200–1000 bp in length and 7.56% of the unigenes were longer than 3000 bp, which was similar to previous transcriptomes of the Amur sturgeon spleen and liver that were based on Illumina sequencing[19,26]
Summary
Sturgeon is an important fish species farmed worldwide, which has significant economic value as an animal protein source, including caviar and meat[1,2]. The hybrid sturgeon (Huso dauricus × Acipenser schrenckii) is one of the five dominant sturgeon strains that was widely bred in China for caviar and meat production[3], showing the advantage on growth and disease resistant[4,5]. With the rapid development of aquaculture, outbreaks of disease caused by bacterial infection lead to high mortality and catastrophic economic losses in hybrid sturgeon aquacultured[6]. The most severe bacterial disease in farmed sturgeons is Aeromonas hydrophila infection in China[7]. As an important aquaculture species in recent years, it is important to understand the defense mechanism of immune system for the control of bacterial infection in hybrid sturgeon (Huso dauricus × Acipenser schrenckii) aquaculture. This study represents the first report of transcriptome analysis of hybrid sturgeon infected with Aeromonas hydrophila. The different genes expression and enrichment analysis of pathways may contribute significant new information regarding the pathogenic mechanisms of the bacterial and the host anti-bacterial immune mechanisms
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