Transcriptional activation of genes involved in oxidative stress in Salmo salar challenged with Piscirickettsia salmonis.

Piscirickettsiosis caused by Piscirickettsia salmonis constitutes one of the main problems in farmed salmonid and marine fishes. The objective of this study was to evaluate the modulation of genes involved in the oxidative stress in the liver and muscle of Salmo salar challenge with low dosage of P. salmonis. The treatment (in duplicate) were as follows: Control injection (culture medium) and P. salmonis injection (1 × 102 PFU/mL) with sampling (liver and muscle) at several time-points during the 42-days experimental period (dpi). In liver, the gene expression of superoxide dismutase (SOD) and acetylcholinesterase (AChE) had differences with the control group only at 7 dpi, compared with glutathione-S-transferase (GST) and heat shock protein 70 (HSP70) that presented increases at 7 and 21 dpi. The glutathione peroxidase (GPx) and catalase (CAT) mRNAs were elevated at 13 and 21 dpi, respectively. While glutathione reductase (GR) and cytochrome P450 (P450) did not show variations in their expression during the experimental course. In muscle, the expression of CAT and AChE was higher than in the control condition at 2 and 42 dpi, respectively. While the number of transcripts SOD, GPx, GR, GST, P450 and HSP70 showed increases at 7- and 42-days post injection. The results suggest a transcriptional activation of genes involved in oxidative stress in both liver and muscle, with expression profiles that were tissue-specific and dependent on the time. This is the first study that reveals the transcriptional participation of all these genes associated with oxidative stress in response to the injection of P. salmonis.