Zebrafish possess an ortholog of IFN-γ together with a related gene (IFN-γ-rel), and studies have suggested that zebrafish IFN-γ (also known as Ifng1) expression is associated with host protection against bacterial infection, while IFN-γ-rel expression is associated with host protection against viral challenge (Igawa et al., 2006; López-Muñoz et al., 2009, 2011; Sieger et al., 2009; Yoon et al., 2016). Here, REL is linked to bacterial infectious disease.