In ferns,the spermatogenesis is a process of de novo formation of the motile apparatuses and the molecular mechanisms of the spermatogenesis were unclear.Centrin,a highly conservative calcium binding protein usually locating in the centrosome,was considered to be the protein that participates the formation of motile apparatuses.Cloning of the centrin gene has some significance for elucidating the molecular mechanism of spermatogenesis of ferns.The present investigation cloned the centrin gene (CtCEN) from the fern model plant,Ceratopteris thalictroides.The full length the cDNA sequence of the CtCEN gene is 1 077 bp,and the structural analysis showed that the gene belongs to be centrin gene of EFhand protein superfamily.Phylogenetic analysis indicated that the CtCEN of the algae,ferns,animal and human,all of which produce sperms with flagella,is clustered in one branch.The CtCEN of angiosperm is clustered in another branch.It is suggested that the centrin may participate the genesis of flagellum.The prokaryotic expression and Western blot analysis showed that the expressed protein of CtCEN can hybridize with the centrin protein antibody of Human,which indicated that the CtCEN belongs to the centrin family.The present studies lay a foundation for the molecular mechanism of the centrin participating formation of motile apparatuses in fern spermatogenesis.