Abstract:
The Janus tyrosine kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathway
plays a critical role in host defense against viral and bacterial infections. STAT proteins are a group of
transcription factors that translocate into the nucleus and are critical for the induction of many genes
crucial for the allergic cascade and immune defense. In the present study, a member of the STAT4 family
was identified from rock bream (RbSTAT4) at the genomic level, and its transcriptional regulation in
response to different pathological stimuli under in vivo conditions was investigated. The genomic
sequence of RbSTAT4 is approximately 15.6 kb in length, including a putative core promoter region and 24
exons interrupted by 23 introns. Bioinformatics analysis of RbSTAT4 identified the presence of typical
and conserved features of the STAT4 family, including the STAT_int domain, STAT alpha domain, STAT
bind domain, linker domain, SH2 domain, and transcriptional activation domain. According to the
phylogenetic analysis, RbSTAT4 exhibited the closest evolutionary proximity with the STAT4 member
from mandarin fish (Siniperca chuatsi). The RbSTAT4 transcript in healthy rock breams was detected to
have ubiquitous expression in 11 different tissues examined, where liver and spleen tissues showed
moderate expressions compared with the highest expression level detected in gill tissue. The timecourse in vivo immune stimulation of rock bream with lipopolysaccharide, poly I:C, live Edwardsiella
tarda, and rock bream iridovirus caused significant transcriptional regulation of the RbSTAT4 expression
in gill, head kidney, and spleen tissues, suggesting that RbSTAT4 is involved in immune regulation
mechanisms and/or signaling cascades, orchestrating against both bacterial and viral pathogens
