Effects of feeding time on complement component C7 expression in Pelteobagrus vachellii subject to bacterial challenge

Shifting the feeding time for fish from daytime to nighttime could alter their digestive behavior, disturb their metabolism, and may affect immune-related genes. This study aimed to clone complement component C7 and analyze the different expression of C7 mRNA in fish fed during either the day or at night and then challenged with Aeromonas hydrophila infection. The Pv-C7 cDNA of Pelteobagrus vachellii contained 2 647 bp with an open reading frame encoding a protein of 818 amino acids. Multiple sequences analysis indicated that Pv-C7 included eight domains, which was similar to results for other species. Quantitative PCR analysis showed that Pv-C7 was mainly expressed in the liver, spleen, intestine and head kidney tissues of healthy P. vachellii. Quantitative PCR analysis showed that C7 mRNA transcript in the liver, spleen and head kidney also increased significantly when the fish were fed at nighttime (20:00). In addition, the expression of Pv-C7 mRNA significantly increased with A. hydrophila challenge in the liver (48–96 h), spleen and head kidney (12–96 h) tissues of P. vachellii. Pv-C7 mRNA expression of the fish fed at nighttime showed significant higher than that in the fish fed at day time at 12–48 h in head kidney and 12–24 h in spleen. This study indicates that altering the feeding time from daytime to nighttime could increase Pv-C7 mRNA expression, and feeding time may affect the immune response involving C7.