SummaryAlthough the JAK/STAT signal

Summary
Although the JAK/STAT signaling pathway is usually involved in antiviral defense, a recent
study suggested that STAT might be annexed by WSSV (white spot syndrome virus) to
enhance the expression of a viral immediate early gene in infected shrimps. In the present
study, we clone and report the first full-length cDNA sequence for a crustacean STAT from
Penaeus monodon. Alignment and comparison with the deduced amino acid sequences of
other STATs identified several important conserved residues and functional domains,
including the DNA binding domain, SH2 domain and C-terminal transactivation domain.
Based on these conserved sequences, a phylogenetic analysis suggested that shrimp STAT
belongs to the ancient STAT family, while the presence of the functional domains suggested
that shrimp STAT might share similar functions and regulating mechanisms with the wellknown
STATs isolated from model organisms. Real-time PCR showed a decreased
transcription level of shrimp STAT after WSSV infection, but a Western blot analysis using
anti-phosphorylated STAT antibody showed an increased level of phosphorylated
(activated) STAT in the lymphoid organ of shrimp after WSSV infection. We further show
that a primary culture of lymphoid organ cells from WSSV-infected shrimp resulted in
activated STAT being translocated from the cytoplasm to the nucleus. This report provides
experimental evidence that shrimp STAT is activated in response to WSSV infection. Our
results support an earlier finding that WSSV does not disrupt JAK/STAT pathway, but on the
contrary benefits from STAT activation in the shrimp host.
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