Molecular Structure And Expression Analysis Of Miichthys Miiuy Members Of Complement Component Gene Family

Fish, the first of true vertebrates, have evolved adaptive immune responses similar to those in higher vertebrates, but the adaptive immunity in fish is inefficient, therefore they should make full use of the well-developed innate immune system to compensate for their rudimentary antibody response. The complement system, one of the most sophisticated innate immune systems, plays a major role in clearing of invading microorganisms. In order to identify the complement component genes including Bf/C2, C4, C5, C6, C7-1, C7-2, C8α, C8β and C8γ, we used available fish genes as queries to search for t he transcriptome and whole genome database of miiuy croaker(unpublished data) by local Blast software. Then we analyze the genomic structure and gene synteny of complement component among bony fish and the RT-PCR is used to analyze the expression patterns of complement component genes in healthy tissues and infected tissues.The result of bioinformatics analysis of Bf/C2 gene indicated that the Bf/C2 c DNA encodes a protein of 767 amino acids with an open reading frame(ORF) of 2301 bp and the genomic structure of miiuy croaker Bf/C2 contains 19 exons and 18 introns, and genomic structure is similar with other fish. The analysis of gene synteny indicated high degree conserved of gene synteny was retained among bony fish. The result of RT-PCR showed that Bf/C2 gene expressed in all healthy tissues but their expression levels were obvious different. After infection with Vibrio anguillarum, Bf/C2 gene expression levels were up-regulated in liver and kidney, but it was down-regulated in spleen.Complement component C4 and C5 were derived from whole genome database of miiuy croaker. Compared with other fish, high degree conserved of genomic structure and gene synteny was retained among bony fish. The result of RT-PCR showed that C4 gene expressed in all healthy tissues but their expression levels were obvious different. After infection with bacteria, the expression of C4 gene was up-regulated in liver, but it was down-regulated in spleen and kidney.In terminal complement component(TCC), duplication of C7 gene was found in bony fish which was the consequence of the fish-specific genome duplication. Although gene duplication is a common evolutionary event in fish, the study of gene duplication of the TCC was little. The result of bioinformatics analysis of C7-1 and C7-2 genes showed that high degree conserved of genomic structure and gene synteny was retained among bony fish, respectively. Besides, other members of TCC also have high degree conserved of gene synteny except for C9. The expression analysis results showed that they were ubiquitously expressed in all ten tested tissues, but their expression levels were obvious different. Higher expression levels of C7-1 were detected in liver, spleen and brain, while lower expression levels were detected in gill, muscle, eye, heart and kidney. For C7-2 gene, higher expressions were detected in liver, spleen and kidney, while lower expressions were detected in eye, gill, brain, muscle, heart and intestine. After bacterial injection, immune response time of C7-1 and C7-2 is different in same tissues. These results indicate that C7-1 and C7-2 genes have different expression patterns and immune response time.