Phylogeny of Slc15 family and response to Aeromonas hydrophila infection following Lactococcus lactis dietary supplementation in Cyprinus carpio.

Solute carrier 15 family (Slc15) are membrane proteins that utilize the proton gradient and negative membrane protential for the transmembrane transporter of di-/tripeptide and peptide-mimetic molecules, in addition, they also play important roles in immunoreaction. In this study, 10 Slc15 genes were identified in the common carp genome database. Comparative genomics analysis showed considerable expansion of the Slc15 genes and verified the four-round whole genome duplication (WGD) event in common carp. Phylogenetic analysis revealed all Slc15 genes of common carp were clustered into orthologous groups indicating the highly conservative during evolution. Besides, the tissues and temporal expression examined by RT-PCR and qRT-PCR showed that most of the Slc15 genes had a narrow tissue distribution and exhibited tissue-specific expression patterns. Expression divergences were observed between these copies proving function divergence after the WGD. Then, we investigated the dietary supplementation effects of three Lactococcus lactis strains on the expression of Slc15 genes in common carp infected by A. hydrophila to find an effective way to treat aquatic diseases. Almost all of the Slc15 genes had an increased expression trend in the early post-challenge stage, and reached the highest expression level at 12h post-challenge. Then, the expression level showed a bluff descent at the last two stages and the expression level reached the lowest at 48 h post-challenge. Slc15 genes expression is actively up-regulated when stimulated by inflammatory factors, which can "amplify" immune signals, and improve the body's defense against foreign invasion in the early stage of the inflammatory response. So activation of the Slc15 genes may be an effective way for infectious disease treatment. As expected, three strains improved the expression of Slc15 genes variously compared with the control/infection groups. The strain 3 of L. lactis had a better induction of Slc15 genes compared with strain 1 and strain 2. It might be applied as a potential activation of Slc15 genes for disease treatment and adding befitting L. lactis may be a good way to protect aquatilia from bacillosis. • This work presented the first identification of Slc15 gene family in common carp. • Comparative genomics and phylogenetic analysis showed considerable expansion of Slc15 gene family and approved the four round whole genome duplication (WGD) event in common carp. • It applied as a potential activation of Slc15 genes for disease treatment and adding befitting L. lactis maybe a good way to protect aquatilia from bacillosis. [ABSTRACT FROM AUTHOR]