Cloning of the IL-1β3 gene and IL-1β4 pseudogene in salmonids uncovers a second type of IL-1β gene in teleost fish

To date two closely related interleukin-1β genes (IL-1β1 and IL-β2) have been found in salmonids. The cloning of trout and salmon IL-1β3, and a salmon IL-1β4 pseudogene reveals that two types of IL-1β genes exist in teleost species. Type I teleost IL-1β genes, including salmonid IL-1β3, share a similar 6 coding exon structure as in tetrapods. Type II teleost IL-1β genes, e.g. salmonid IL-1β1–2, lack one or two coding exons at their 5′-end, and share higher identities within this subgroup than within the type I subgroup. Both types of IL-1β genes have been found in species of Salmoniformes, Perciformes and Beloniformes, suggesting the divergence occurred early in teleost evolution. Trout IL-1β3 is highly expressed in ovary suggesting a role in reproduction. A relatively high constitutive expression in gills, spleen and kidney and the up-regulation by PAMPs, proinflammatory cytokines and viral infection suggests IL-1β3 also has a role in inflammation and host defence.

► Cloning of IL-1β3 in salmonids uncovers two types of IL-1βs in teleost fish. ► A teleost fish species can possess either one or both types of IL-1β genes. ► Teleost fish type I IL-1βs have a six coding exon gene organisation as in tetrapods. ► Type II IL-1βs share higher identities within teleosts and miss one or two exons. ► Salmonid IL-1β3 may have roles in reproduction, inflammation and immune defence.