Identification and expression profiles of granzyme genes in immune response from Nile tilapia (Oreochromis niloticus)

Granzymes (Gzms) are crucial cytotoxic molecules involved in cell-mediated immunity in mammals. However, their roles in teleost fish, such as Nile tilapia , were less understood. In this study, we focused on the identification of granzyme genes ( On Gzm s ) from Nile tilapia ( Oreochromis niloticus ) and the potential functions in anti-infectious immunity, as well as their expression patterns in response to interleukin-2 stimulation. Eleven Gzm genes were identified in tilapia , including GzmA-1 , GzmA-2 , GzmK , GzmB-1 , GzmB-2 , GzmB-3 , GzmH-1 , GzmH-2 , GzmG , GzmF , and GzmE , which contain conserved serine protease active sites. On Gzms were categorized into four groups through homology analysis at a shared locus. Gene replication processes, such as whole-genome replication specific to teleost and unequal crossing over of tandem genes, may lead to multigene copies of On Gzm genes. It appeared that the vertebrate GzmA/K originated from a common ancestor in terms of evolution. After Streptococcus agalactiae , Aeromonas hydrophila , Edwardsiella piscicida and Poly (I:C) challenges, expression of OnGzms was significantly up-regulated only in response to E. piscicida (an intracellular bacterium) infection, indicating potential functions of On Gzms involving in combating intracellular infection by the bacterium E. piscicida . Stimulation with r On IL-2 led to increased expression of OnGzms in leukocytes, suggesting involvement in cell-mediated cytotoxicity. These findings enriched the knowledge of potential roles in resisting E. piscicida intracellular infection of granzyme genes in teleost fish. • Eleven granzyme genes categorized in four groups were found in Oreochromis niloticus . • OnGzms were markedly up-regulated following Edwardsiella piscicida challenge. • Upon r On IL-2 stimulation, OnGzms transcription in leukocytes significantly increased.