The interferon-induced GTP-binding protein Mx is responsible for a specific 
antiviral state against a broad spectrum of viral infections that are induced by 
type-I interferons (IFN α/β) in different vertebrates. In this study, the Mx 
gene was isolated from the constructed mullet cDNA database. Structural features 
of mullet Mx (MuMx) were analyzed using different in-silico tools. The pairwise 
comparison revealed that the MuMx sequence was related to Stegastes partitus Mx 
with an 83.7% sequence identity, whereas MuMx was clustered into the teleost 
category in the phylogentic analysis. Sequence alignment showed that the 
dynamin-type guanine nucleotide-binding domain (G_DYNAMIN_2), central 
interactive domain (CID), and GTPase effector domain (GED) were conserved among 
Mx counterparts. The transcriptional expression of MuMx was the highest in blood 
cells from unchallenged fish. The temporal mRNA profile showed that MuMx 
expression was significantly elevated in all tissues, including blood, spleen, 
head kidney, liver, and gills after the injection of polyinosinic-polycytidylic 
acid (poly I:C) at many time points. Moreover, MuMx expression increased 
slightly, in the blood, spleen, and head kidney at a few time points after the 
injection of lipopolysaccharide (LPS) and Lactococcus garvieae (L. garvieae). 
Results of the subcellular localization analysis confirmed that the MuMx protein 
was highly expressed in the cytoplasm. The analysis of the gene expression of 
the viral hemorrhagic septicemia virus (VHSV) under conditions of MuMx 
overexpression confirmed the significant inhibition of viral transcripts. The 
cell viability (MTT) assay and VHSV titer quantification with the presence of 
MuMx indicated a significant reduction in virus replication. Collectively, these 
findings suggest that Mx is a specific immune-related gene that elicits crucial 
antiviral functions against viral antigens in the mullet fish.