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Bone morphogenetie proteins(BMPs)were thought to play an important role in the regulation of cell proliferation,survival,differentiation and apoptosis in many vertebrates and invertebrates through TGF-β signaling pathway.Although the TGF-β signaling pathway exists in schistosomes,BMP homologue,the ligand of TGF-β in Schistosomajaponicum is still uncovered.In this study,a bone morphogenetic protein(BMP)homologue of S.japonicum has been cloned and characterized.The SjBMP cDNA is 3020 bp in full length,encodes 928 amino acids which include a TGF-β superfamily conserved domain at the C-terminal.By BLAST analysis,SjBMP shows 68%,51% and 43% homology with BMP from Schistosoma mansoni,Schmidtea mediterranea and Dugesia japonica at the amino acid level.Based on Real-time PCR,SjBMP were expressed throughout the lung-phase schistosomula,21-day liver-phase schistosomula,50-day adult male and female worms,and eggs,and there were 27~ and 37~ folds of SjBMP transcripts in lung-phase schistosomula and eggs,respectively; and more in adult male worm than those in the adult female,in which the hepatic schistosomula was set as calibrator.In-situ hybridization based on FITC-labeled specific antisense oligonucleotide probes localized SjBMP mRNA to the egg shell,females ovary,integument and tunnel epithelium,males integument and tunnel epithelium.After treatment with double-stranded RNA(dsRNA)at the concentration of 8×10-2 μg/ml,which was added to culturing medium every other day within a week,the level of SjBMP rnRNA in the cultured adult mix-sex S.japonicum decreased at a fluctuant rate of~25%-98% within 7 days compared with that of the blank controlled.On the 2nd day,the eggs produced by per pair of worms decreased at a rate of 28.7% and the percent of normal eggs also decreased (12.7% vs.4.3%)in the dsRNA treated group when compared with those of the control group,but no difference was detected on the 7th day,with the eggs of the untreated worms also mostly abnormal as similar as those of the treated.In addition,no distinct difference in the morphological structure of adult worms was observed.So,the preliminary in vitro experiment showed SjBMP may be involved in the oviposition behavior of S.japonicum,and further studies based on recombinant virus vector induced steady knockdown of SjBMP or in vivo experiments are planned for deeper investigation.