Molecular Characterization And Expression Analysis Of Interleukin 15(IL15)and Interleukin-15 Receptor Subunit Alpha(IL15Rα)in Dojo Loach(Misgurnus Anguillicaudatus):Their Salient Roles During Flavobacterium Columnare G4、I.multifiliis And Saprolegnia Spp.

Interleukin 15（IL15）is a pleiotropic cytokine that participates in innate and adaptive immunity along with its receptorα-chain（IL15Rα）.In order to investigate the potential roles of IL15 and IL15Rαin dojo loach（Misgurnus anguillicaudatus）,we firstly cloned the cDNA sequence of Ma-IL15 and Ma-IL15Rα,which contain 1096bp and 1236bp and code proteins of 193 amino acids and 210 amino acids,respectively.A short signal peptide and Pfam IL15 domain were found in Ma-IL15,while a highly conserved sushi domain existed in Ma-IL15Rα.Ontogeny analysis indicated that significantly increased expression of Ma-IL15 and Ma-IL15RαmRNA were detected in larvae from 1d to 7d post hatching,while relative high expression levels were detected in both systematic and mucosal immune-related tissues of adult dojo loach.Then three dojo loach infection models with F.columnare G₄,I.multifiliis and Saprolegnia parasitica were constructed,which resulted in increased skin mucous cells and serious lesions in gill.Ma-IL15 and Ma-IL15Rαshowed different expression patterns in different tissues during three infection models.Ma-IL15RαmRNA was found to be more significantly elevated than Ma-IL15 after infection with F.columnare G₄ in all examined tissues including kidney,spleen,gill and skin.I.multifiliis infection induced higher expression of Ma-IL15in mucosal tissues including skin and gill,while it mainly increased Ma-IL15Rαexpression in kidney.Moreover,our study firstly evaluated the influence of fungal infection on IL15 and IL15Rαexpression in teleost,and it is interesting to find that both Ma-IL15 and Ma-IL15Rαexpression showed consistent up-regulation after Saprolegnia parasitica infection compared to two other infection models.Therefore,our results suggest that Ma-IL15 and Ma-IL15Rαpossess important defensive roles in systematic and mucosal tissues of dojo loach during bacterial,fungal and parasitic infection.