Molecular Cloning and Functional Analysis of IRF-1 in the Asian Swamp Eel (Monopterus albus)

Interferon regulatory factors (IRFs) have been studied in mammals and various fish species, but not in the Asian swamp eel (Monopterus albus). Complete IRF-1 cDNA sequence and genomic DNA sequence of M. albus were cloned. The IRF-1 gene, named maIRF1, spanned 3.5 kb from the transcription start site to the polyadenylation signal. The maIRF mRNA contained an open reading frame of 885 nucleotides, which translated into 294 amino acids. The overall amino acid cDNA sequences shared 42.5-81.0% identity with IRF-1 in Mandarin (Siniperca chuatsi), Crucian carp (Carassius auratus), Atlantic salmon (Salmo salar), Grass carp (Ctenopharyngodon idella), Zebrafish (Danio rerio) and Fugu (Takifugu rubripes), and 36.6-38.0% identity with IRF-1 in Chicken (Gallus gallus), Frog (Xenopus tropicalis), Human (Homo sapiens) and Mouse (Mus musculus). Quantitative real-time PCR revealed that maIRF1 expression changed little during the three different growth stages (female, intersex, male). Moreover, maIRF was constitutively expressed in all analyzed organs, being most predominantly expressed in the trunk kidneys and blood and the least in muscle tissue. The expression levels of maIRF1 were tested in trunk kidney and spleen after challenge with synthetic double-stranded RNA poly I:C and lipopolysaccharide (LPS). It was found that maIRF1 expression changed significantly 24-72 h after injection (P<0.05), which demonstrated that maIRF1 plays an important role in congenital immunity and adaptive immunity of M. albus.