Abstract
Tilapia (Oreochromis sp.) is one of the important economical fishes in the world. Streptococcosis is commonly found in tilapia, causing severe and devastating effects in tilapia cultures. Streptococcus agalactiae and Streptococcus iniae are the predominant pathogens causing tilapia streptococcosis. To understand the molecular mechanisms underlying differential streptococcal infection patterns, Nile tilapias (Oreochromis niloticus) were infected by 1 × 107 CFU/mL S. agalactiae, 1 × 107 CFU/mL S. iniae, and 1 × 107 CFU/mL S. agalactiae and S. iniae (1:1), respectively, and transcriptome analysis was conducted to the intestine samples of Nile tilapia (Oreochromis niloticus) at 6, 12, 24 h, and 7 days post-infection. A total of 6,185 genes that differentially expressed among groups were identified. Eight differentially expressed genes (DEGs) including E3 ubiquitin-protein ligase TRIM39-like, C-X-C motif chemokine 10-like(CXCL 10), C-C motif chemokine 19-like, interleukin-1 beta-like, IgM heavy chain VH region, partial, IgG Fc-binding protein, proteasome subunit beta type-8 (PSMB8), and ATP synthase F(0) complex subunit B1, mitochondrial that involved in the immune system were selected, and their expression levels in the coinfection group were significantly higher than those in either of the single infection groups. These genes were associated with four different KEGG pathways. Additionally, the differential expression of eight DEGs was validated by using the RT-qPCR approach, and their immunological importance was discussed. The results provided insights into the responses of tilapia against S. agalactiae and S. iniae at the transcriptome level, promoting our better understanding of immune responses for aquatic animal against Streptococcus.
Highlights
Tilapia (Oreochromis niloticus) is an economic and important aquaculture fish species in the world
The maximum number of differentially expressed genes (DEGs) in all experimental groups appeared at 24 h (3,792, 3,319, and 3,064, respectively) (Figure 1)
Our results revealed that more ubiquitin proteasomes were formed in the tilapia to participate in the immune response against the coinfection of S. agalactiae and S. iniae
Summary
Tilapia (Oreochromis niloticus) is an economic and important aquaculture fish species in the world. As a common disease caused by pathogenic bacteria, streptococcosis has devastating effects in tilapia cultures (Anshary et al, 2014). In 2019, the economic losses for the tilapia aquaculture industry caused by S. agalactiae and S. iniae have reached around 2.5 billion RMB (Huang et al, 2014; Tavares et al, 2018; Shiry et al, 2019). S. agalactiae is known as group B Streptococcus (Brown, 1939) Both of them are recognized as causative agents of zoonosis with a broad host range, including horse, pig, and fish (Mohan, 1947; Monteverde and Simeone, 1951; Poppert et al, 2009). Previous research studies on tilapia infected by S. agalactiae and S. iniae focused mainly on the isolation, identification and typing of strains, screening of drugs for the prevention and treatment of Streptococcus-infected tilapia, the drug resistance, and vaccine development (Suanyuk et al, 2008; Cai et al, 2020; De Sousa et al, 2021). The knowledge of the molecular mechanisms in immune response aspects against S. agalactiae and S. iniae in the intestine of tilapia is still limited
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
