Specificity　protein　(Sp)　belong　to　a　transcription　factor　family　that　contains　nine　subgroups　with　essential　functions　in　development,　including　skeletogenesis,　tooth　development,　neural　tube　closure,　and　limb　formation.　In　molluscs,　functions　of　the　Sp　protein　family　members　have　not　been　reported　in　detail.　In　this　study,　we　report　the　first　Sp　protein-encoding　gene　in　Pinctada　fucata.　We　named　the　translated　protein　Pf-Sp8/9,　based　on　the　phylogenetic　development　tree　constructed　using　Sp　protein　sequences　from　six　model　organisms,　which　showed　that　it　was　a　Sp8/9　homolog.　Alignment　of　the　Pf-Sp8/9　sequence　with　the　amino　acid　sequences　of　related　proteins　showed　that　Pf-Sp8/9　had　conserved　domains,　including　three　DNA-binding　motifs.　The　tissue　distribution　showed　that　while　Pf-Sp8/9　mRNA　expression　was　detected　in　all　tested　tissues,　it　was　particularly　high　in　the　mantle.　The　luciferase　reporter　assay　results　showed　that　Pf-Sp8/9　had　the　ability　to　activate　the　transcription　of　a　number　of　matrix　proteins.　The　expression　pattern　of　Pf-Sp8/9　during　P.　fucata　pearl　sac　development　was　similar　to　that　of　some　genes　that　encode　matrix　proteins,　suggesting　Pf-Sp8/9　may　be　involved　in　mantle　related　physiological　activities　and　biomineralization.　(C)　2016　Elsevier　Inc.　All　rights　reserved.