Expression Differences of Stress and Immunity Genes in Rainbow Trout (Oncorhynchus mykiss, Walbaum 1792) with Different Bacterial Fish Diseases

Abstract

The aim of this study was to determine the changes in the mRNA transcription levels of HSP70 and IGF genes related to stress and immunity in Oncorhynchus mykiss obtained from fish farms, to determine the phenotypic and antimicrobial properties of the bacteria isolated in the study and to compare the results according to different diseases. Accordingly, six fish from each fish farm, a total of 30 fish were sampled. Bacterial identification, inoculations were carried out from the tissue samples taken from the kidney and symptomatic surfaces of fish samples in TSA. Primary cultures were obtained after incubation periods at 21 and 37oC. Gram staining, catalase, and oxidase tests were performed. Forty-six biochemical and 26 antimicrobial tests were performed using BD Phoenix ID Panels. Muscle tissue was used to determine mRNA gene expression differences and the tissues were preserved at -80°C in RNAlater storage solution. Following the RNA isolation and cDNA synthesis, a real-time PCR procedure was performed with b-Actin (ACTB), Insuline-like growth factor (IGF) and HSP70 Gene Primer Array system. Enterococcus faecium (E. faecium), Lactococcus garvieae (L. garvieae) and Staphylococcus aureus (S. aureus) agents were isolated in the study. These bacteria were identified with 91-99% similarity ratios. No disease agents in the gene expressions of the fish samples in were isolated and they were therefore used as controls. Compared to the control group, heat shock protein (HSP) mRNA expression was upregulated in fish tissues infected with E. faecium, S. aureus, and L. garvieae whereas no significant increase was determined in fish tissues infected with S. aureus. IGF mRNA gene expression was upregulated in all infected tissues. IGF expression was upregulated at the highest level in fish tissues infected with L. garvieae.