EVIDENCES FOR THE COMPLEMENT GENES INVOLVE IN INNATE IMMUNITY OF ROCK BREAM Oplegnathus fasciatus WITH MOLECULAR, TRANSCRIPTIONAL AND FUNCTIONAL ASPECTS OF FOUR COMPLEMENT GENES  

In order to explore the teleost immunity, we are studying the immune relevant genes of rock bream fish through a combined genomic and transcriptomic approach. The complement system is the killing of bacteria by antibodies and phagocytic cells from an organism. It is a humoral system of innate immunity and a link to adaptive immune responses. Here, we have characterized four complement genes from rock bream (Oplegnathus fasciatus). C1r and C1s enzymes are initiating the complement classical pathway where CfD is essential for the activation of the alternative complement pathway. CPN inactivates the complement anaphylatoxins of C3a, C4a, and C5a. Molecular immunologists interested to carry out their studies concerning on the characterization of innate immune genes in teleost species which are under the threat of pathogens. Present study, we sought to characterize OfC1r, OfC1s, OfCfD and OfCPN counterparts identified from Oplegnathus fasciatus transcriptome database. Putative amino acid sequences were aligned with respective homolog sequences to discover their characteristic features. Genomic structural features were determined using the gDNA sequences aligned with cDNA sequences through SPIDEY program. Transcriptional results were obtained through qPCR analysis. Recombinant proteins were used to determine the protease activity using the protease assay kit. According to the bioinformatics studies, OfC1r bears 704 aa and OfC1s bears 691aa. Both C1r and C1s genes consist with conserved CUB, calcium binding EGF, CCP and serine protease domains. OfCfD bears 239 aa and a conserved serine protease trypsin domain. OfCPN comprise 448 aa with Zn binding signatures. Rock bream complement components consist with different exons (OfC1r; 13, OfC1s; 11, OfCfD; 5 and OfCPN; 9) in their gDNA. As the complement genes, they were exhibited an extremely strong transcription in liver spleen and blood tissues. The temporal assessment of OfC1r and OfC1s under the E. tarda and S. iniae pathological infections showed a significant up-regulation of corresponding transcripts at 6 h post infection in liver tissue. Whereas, OfCfD was up-regulated at 12 h post infection with the S. iniae and LPS challenges in spleen tissue. Findings of the current study collectively provide an overall understanding on the pathogenic bacterial mediated expression of the complement signaling genes of teleost origin. Nevertheless, OfC1r, OfC1s and OfCfD are serine proteases which do proteolysis during the complement cascade system.