Cloning and gene expression of signal transducers and activators of transcription (STAT) homologue provide new insights into the immune response and nucleus graft of the pearl oyster Pinctada fucata

• Signal transducers and activators of transcription (STAT) homologue was isolated from Pinctada fucata.
• PfSTAT showed relatively low identity with vertebrate and other invertebrate STATs.
• PfSTAT is involved in the immune response to poly I:C stimulation.
• PfSTAT plays a role in the nucleus grafting operation.

The signal transducers and activators of the transcription (STAT) family play an important role in regulatory and cellular functions by regulating the expression of a variety of genes, including cytokines and growth factors. In the present study, a Pinctada fucata STAT protein, termed PfSTAT, was described. The deduced amino acid sequence of PfSTAT contains the conserved STAT_bind domain and the SH2 domain, and the additional Bin/Amphiphysin/Rvs (BAR) domain, but does not have STAT_alpha and STAT_int domains. Multiple sequence alignments revealed that PfSTAT showed relatively low identity with vertebrate and other invertebrate STATs, and phylogenetic analysis indicated that the evolution of STAT may have been more complex and ancient. Gene expression analysis revealed that PfSTAT is involved in the immune response to polyinosinic–polycytidylic acid (poly I:C) stimulation and in the nucleus insertion operation. This study contributes to a better understanding of PfSTAT in protecting the pearl oyster from disease or injury caused by grafting.