Abstract: Two housekeeping genes, 18S rRNA and βactin, were cloned as endogenous genes for relative quantification of an antimicrobial peptide hepcidin in large yellow croakers (Pseudosciaena crocea) using the realtime RTPCR. In comparision of the slopes of the relative standard curves between the two endogenous genes and the target gene, a relative quantification method for hepcidin gene using 18S rRNA as the calibrator gene was established. Results obtained with this method were consistent with the rusults from Northernblot, suggesting feasibility and effectiveness of the method. This paper provides an effective method to investigate expression patterns and induction profiles of the hepcidin gene in large yellow croakers, and other immunityrelated genes in fish bodies. The cloned fragments of 18S rRNA and βactin genes from the large yellow croaker have been submitted to the GenBank, which have provided accession numbers.

Key words: Pseudosciaena crocea, antimicrobial peptide, house-keeping gene, realtime quantitative PCR, RT-PCR