Species and tissue expression of iron regulation mechanisms. (A) hepcidin-1 was highly up-regulated in the anterior kidney of pink salmon early in the infection period (day three and six only). Chum salmon highly increased hepcidin-1 expression in the anterior kidney and more moderately in the skin. Atlantic salmon up-regulated hepcidin-1 in the skin but not in the anterior kidney (hepcidin-1 data shown is from qPCR). Boxplot displays median and interquartile range, and circles are outliers. *denotes p < 0.05; **denotes p < 0.001. Hepcidin-1 induction was a general response to the infection, whereas other iron homeostasis mechanisms, such as (B) reduction of expression of the heme biosynthesis pathway, were specific to pink salmon. Boxes indicate fold change for day 3, 6 and 9 post infection; an x indicates no probe for analysis, and an empty box indicates no significant difference in expression (heme biosynthesis transcripts shown are from microarray data). Image adapted from: Wikimedia Commons “Heme synthesis” Creative Commons Attribution-ShareAlike 3.0 Unported.