Relative expression levels of probable serine carboxypeptidase, cathepsin D, caspase-6, protein S100 and tubulin alpha in the posterior intestine of rainbow trout. Quantitative real-time PCR shows mean relative expression profiles of each selected gene in the posterior intestine of rainbow trout in response to Y. ruckeri biotype 1 (CSF007-82) and biotype 2 (A7959-11) at different time points. Relative gene expression changes in each gene were determined in the exposed and control posterior intestine samples by the CFX Manager Maestro Software in normalized expression mode (∆∆Cq), using elongation factor alpha 1 as a reference at each time point. A Probable serine carboxypeptidase CPVL, B cathepsin D, C caspase 6, D protein S100, and E tubulin alpha. Stars indicate statistically significant differences in the gene expression compared to the control group. Error bars indicate standard deviation (n = 9).