Molecular characterization and expression analysis of complement components C3 and C9 in largemouth bronze gudgeon (Coreius guichenoti) in response to Ichthyophthirius multifiliis infection

Abstract

Largemouth bronze gudgeon (Coreius guichenoti) is a fish endemic to the middle and upstream reaches of the Yangtze River in China. Indoor culture and domestication of C. guichenoti have yet to see success in part because of Ichthyophthirius multifiliis infection, which causes 100% mortality in these fish. Here, we investigated whether the complement components C3 and C9 in C. guichenoti play a role in immune reactions against I. multifiliis. Full-length C3 and C9 cDNA sequences were determined and analyzed. The C3 cDNA sequence comprised 5142 bp encoding 1643 amino acids. The C9 cDNA sequence comprised 2206 bp with an open reading frame of 2085 bp. The mRNA expression of C3 and C9 genes was detected in the liver, spleen, and trunk kidney, and as well as that of C3 gene in head kidney. I. multifiliis infection significantly upregulated mRNA expression of C3 and C9 in liver and spleen. However, no transcript was detected in the skin of C. guichenoti post-infection with I. multifiliis, and might be responsible for C. guichenoti to be vulnerable to the parasite. The results suggest that C3 and C9 are involved in defense against the ectoparasite I. multifiliis, and promote understanding function of the complement components C3 and C9 in C. guichenoti.