Abstract
Pacu (Piaractus mesopotamicus) is a Neotropical fish of major importance for South American aquaculture. Septicemia caused by Aeromonas hydrophila bacteria is currently considered a substantial threat for pacu aquaculture that have provoked infectious disease outbreaks with high economic losses. The understanding of molecular aspects on progress of A. hydrophila infection and pacu immune response is scarce, which have limited the development of genomic selection for resistance to this infection. The present study aimed to generate information on transcriptome of pacu in face of A. hydrophila infection, and compare the transcriptomic responses between two groups of time-series belonging to a disease resistance challenge, peak mortality (HM) and mortality plateau (PM) groups of individuals. Nine RNA sequencing (RNA-Seq) libraries were prepared from liver tissue of challenged individuals, generating ∼160 million 150 bp pair-end reads. After quality trimming/cleanup, these reads were assembled de novo generating 211,259 contigs. When the expression of genes from individuals of HM group were compared to individuals from control group, a total of 4,413 differentially expressed transcripts were found (2,000 upregulated and 2,413 downregulated candidate genes). Additionally, 433 transcripts were differentially expressed when individuals from MP group were compared with those in the control group (155 upregulated and 278 downregulated candidate genes). The resulting differentially expressed transcripts were clustered into the following functional categories: cytokines and signaling, epithelial protection, antigen processing and presentation, apoptosis, phagocytosis, complement system cascades and pattern recognition receptors. The proposed results revealing relevant differential gene expression on HM and PM groups which will contribute to a better understanding of the molecular defense mechanisms during A. hydrophila infection.
Highlights
Disease outbreaks are considered a primary constraint and a continuous challenge to the growth of aquaculture sector (FAO, 2018)
We found the Interleukin-1 receptor type 1 (IL1R1) and Interleukin-1 receptor type 2 (IL1R2) transcripts upregulated in HM and PM groups
Transcriptome analysis by RNA-seq allowed the identification and comparative quantification of gene expression in pacu infected by A. hydrophila
Summary
Disease outbreaks are considered a primary constraint and a continuous challenge to the growth of aquaculture sector (FAO, 2018). Detrimental effects due improper management practices, high-density culture systems and fluctuating water parameters have facilitated the spreading of bacteria or other pathogens, resulting in frequent and often severe disease outbreaks. This scenario has led to the billions of dollars in losses to aquaculture every year, that may exceed 40% of global capacity of production (Lafferty et al, 2015; Stentiford et al, 2017; Owens, 2019). The incidence of sanitary problems linked to intensification of fish production from South America have resulted in large mortalities of Pacu (Piaractus mesopotamicus), one of the most important native fish species produced in Brazil (IBGE, 2016; Woynárovich and Van Anrooy, 2019). One of the main causes of disease associated with large mortalities for this species is the infection by Aeromonas hydrophila (Carraschi et al, 2012; Farias et al, 2016; Mastrochirico-Filho et al, 2019)
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
