RNA-Seq-Based Analysis of Cortisol-Induced Differential Gene Expression Associated with Piscirickettsia salmonis Infection in Rainbow Trout (Oncorhynchus mykiss) Myotubes

Abstract

Salmonid rickettsial septicemia (SRS) is the major infectious disease of the Chilean salmonid aquaculture industry caused by Piscirickettsia salmonis. Intensive farming conditions generate stress and increased susceptibility to diseases, being skeletal muscle mainly affected. However, the interplay between pathogen infection and stress in muscle is poorly understood. In this study, we perform an RNA-seq analysis on rainbow trout myotubes that are pretreated for 3 h with cortisol (100 ng/mL) and then infected with P. salmonis strain LF-89 for 8 h (MOI 50). Twelve libraries are constructed from RNA samples (n = 3 per group) and sequenced on Illumina HiSeq 4000. A total of 704,979,454 high-quality reads are obtained, with 70.25% mapped against the reference genome. In silico DETs include 175 total genes—124 are upregulated and 51 are downregulated. GO enrichment analysis reveals highly impacted biological processes related to apoptosis, negative regulation of cell proliferation, and innate immune response. These results are validated by RT-qPCR of nine candidate transcripts. Furthermore, cortisol pretreatment significantly stimulated bacterial gene expression of ahpC and 23s compared to infection. In conclusion, for the first time, we describe a transcriptomic response of trout myotubes infected with P. salmonis by inducing apoptosis, downregulating cell proliferation, and intrinsic immune-like response that is differentially regulated by cortisol.

Reference Intervals for Blood Biomarkers in Farmed Atlantic Salmon, Coho Salmon and Rainbow Trout in Chile: Promoting a Preventive Approach in Aquamedicine

“…Blood biomarkers profiling in salmonids has been used most frequently in the characterization of infectious diseases, defining and quantifying systemic functional profiles such as liver, renal, cardiac, pancreatic and other functions [ 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 ]. Furthermore, the number and percentages of the different types of leukocytes present have been demonstrated to change in response to infection and stress in salmonids [ 29 , 30 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 ].…”

Why Does Piscirickettsia salmonis Break the Immunological Paradigm in Farmed Salmon? Biological Context to Understand the Relative Control of Piscirickettsiosis

“…Trout skeletal muscle is an immunologically active organ that can implement an early immune response against P. salmonis ( 101 ). In fact, this response could be differentially regulated by cortisol, which could lead to bacterial outbreaks in muscle under stress conditions ( 102 , 103 ). A common transcriptional response associated with clathrin-mediated endocytosis and iron homeostasis has been shown in different tissues ( 12 , 96 , 97 , 104 , 105 ).…”

Effect of florfenicol on Piscirickettsia salmonis biofilm formed in materials used in salmonid nets, nylon and high‐density polyethylene

“…Despite all the pathology recorded in several countries of the north hemisphere (Rozas & Enríquez, 2014), the main disease outbreaks have been registered in Chile, generating severe economic losses and it being considered as a major economic threat to the sustainability of the Chilean salmon industry (Sernapesca, 2022a). In this sense, it is important to note that the intensive farming conditions generate stress due to a high stocking density and consequently, a competition for food among cultured fish, which increase the susceptibility to several infectious diseases, such as bacterial kidney disease, caligidosis and Piscirickettsiosis (Figueroa et al, 2019; Zuloaga et al, 2021). Nowadays, vaccines are the main prevention strategy against Piscirickettsiosis.…”