Differential Expression Genes of the Head Kidney and Spleen in Streptococcus iniae-Infected East Asian Fourfinger Threadfin Fish (Eleutheronema tetradactylum)

Shun Maekawa; Pei-Chi Wang; Shih-Chu Chen

doi:10.3390/ijms24043832

Differential Expression Genes of the Head Kidney and Spleen in Streptococcus iniae-Infected East Asian Fourfinger Threadfin Fish (Eleutheronema tetradactylum)

Int J Mol Sci. 2023 Feb 14;24(4):3832. doi: 10.3390/ijms24043832.

Authors

Shun Maekawa^{1

2

3}, Pei-Chi Wang^{1

2}, Shih-Chu Chen^{1

2}

Affiliations

¹ Department of Veterinary Medicine, College of Veterinary Medicine, National Pingtung University of Science and Technology, Pingtung 91201, Taiwan.
² International Degree Program of Ornamental Fish Technology and Aquatic Animal Health, International College, National Pingtung University of Science and Technology, Pingtung 91201, Taiwan.
³ General Research Service Centre, National Pingtung University of Science and Technology, Pingtung 91201, Taiwan.

Abstract

Streptococcus iniae is a Gram-positive bacterium and is considered a harmful aquaculture pathogen worldwide. In this study, S. iniae strains were isolated from East Asian fourfinger threadfin fish (Eleutheronema tetradactylum) reared on a farm in Taiwan. A transcriptome analysis of the head kidney and spleen was performed in the fourfinger threadfin fish 1 day after infection using the Illumina HiSeq™ 4000 platform for RNA-seq to demonstrate the host immune mechanism against S. iniae. A total of 7333 genes based on the KEGG database were obtained after the de novo assembly of transcripts and functional annotations. Differentially expressed genes (DEGs) (2-fold difference) were calculated by comparing the S. iniae infection and phosphate-buffered saline control group gene expression levels in each tissue sample. We identified 1584 and 1981 differentially expressed genes in the head kidney and spleen, respectively. Based on Venn diagrams, 769 DEGs were commonly identified in both the head kidney and spleen, and 815 and 1212 DEGs were specific to the head kidney and spleen, respectively. The head-kidney-specific DEGs were enriched in ribosome biogenesis. The spleen-specific and common DEGs were found to be significantly enriched in immune-related pathways such as phagosome, Th1, and Th2 cell differentiation; complement and coagulation cascades; hematopoietic cell lineage; antigen processing and presentation; and cytokine-cytokine receptor interactions, based on the KEGG database. These pathways contribute to immune responses against S. iniae infection. Inflammatory cytokines (IL-1β, IL-6, IL-11, IL-12, IL-35, and TNF) and chemokines (CXCL8 and CXCL13) were upregulated in the head kidney and spleen. Neutrophil-related genes, including phagosomes, were upregulated post-infection in the spleen. Our results could offer a strategy for the treatment and prevention of S. iniae infection in fourfinger threadfin fish.

Keywords: East Asian fourfinger threadfin fish (Eleutheronema tetradactylum); RNA-seq; Streptococcus iniae; head kidney; immune response; spleen.

MeSH terms

Animals
Fish Diseases*
Fishes
Head Kidney
Spleen
Streptococcal Infections*
Streptococcus iniae

Grants and funding

(grant number MOST111-2313-B-020-004)/the National Science and Technology Council, Taiwan