Abstract
Lymphocystis disease virus (LCDV) infection may induce a variety of host gene expression changes associated with disease development; however, our understanding of the molecular mechanisms underlying host-virus interactions is limited. In this study, RNA sequencing (RNA-seq) was employed to investigate differentially expressed genes (DEGs) in the gill of the flounder (Paralichthys olivaceus) at one week post LCDV infection. Transcriptome sequencing of the gill with and without LCDV infection was performed using the Illumina HiSeq 2500 platform. In total, RNA-seq analysis generated 193,225,170 clean reads aligned with 106,293 unigenes. Among them, 1812 genes were up-regulated and 1626 genes were down-regulated after LCDV infection. The DEGs related to cellular process and metabolism occupied the dominant position involved in the LCDV infection. A further function analysis demonstrated that the genes related to inflammation, the ubiquitin-proteasome pathway, cell proliferation, apoptosis, tumor formation, and anti-viral defense showed a differential expression. Several DEGs including β actin, toll-like receptors, cytokine-related genes, antiviral related genes, and apoptosis related genes were involved in LCDV entry and immune response. In addition, RNA-seq data was validated by quantitative real-time PCR. For the first time, the comprehensive gene expression study provided valuable insights into the host-pathogen interaction between flounder and LCDV.
Highlights
Lymphocystis disease virus (LCDV), which belongs to the lymphocystivirus genus within Iridoviridae family and has a dsDNA genome, is the causative agent of lymphocystis disease, which has affected more than 140 marine and freshwater fish species worldwide, including flounder (Paralichthys olivaceus), an economically important fish in Asian countries such as Japan, Korea, and China [1], resulting in great economic losses [2,3,4,5]
The flounder suffering from lymphocystis disease is characterized by the appearance of tumor-like nodules consisting of hypertrophied lymphocystis cells on the skin, fins, gill, mouth, and even the internal organs, leading to loss of commercial value and sometimes causing death [1]
The resultant data disclosed a large amount of novel gene information and showed significant expression changes in response to LCDV infection, which would promote a better understanding of pathogenesis and fish defense mechanisms to LCDV infection
Summary
Lymphocystis disease virus (LCDV), which belongs to the lymphocystivirus genus within Iridoviridae family and has a dsDNA genome, is the causative agent of lymphocystis disease, which has affected more than 140 marine and freshwater fish species worldwide, including flounder (Paralichthys olivaceus), an economically important fish in Asian countries such as Japan, Korea, and China [1], resulting in great economic losses [2,3,4,5]. The mechanism of lymphocystis cell formation from the viewpoint of differentially expressed genes (DEGs) in the infected flounder fin has been investigated recently by using microarrays [15]; microarray technology has limited capacity to identify novel transcriptional profiles and quantify transcripts at a relatively low level [16]. The gill from the LCDV-infected and non-infected control groups at one week post intramuscular injection [24] was used to prepare sequencing libraries, and the transcriptional sequence of flounder gill and a comparative analysis of transcriptome data between the two groups was performed using Illumina HiSeq 2500 sequencing platform. QRT-PCR was conducted to verify several randomly selected DEGs. The resultant data disclosed a large amount of novel gene information and showed significant expression changes in response to LCDV infection, which would promote a better understanding of pathogenesis and fish defense mechanisms to LCDV infection
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