Characterization,Evolution and Expression of the Calmodulinl Genes from the Amphioxus Branchiostoma belcheri tsingtauense

Two full-length cDNAs,named CaM1a and CaM1b,encoding the highly conserved calmodulinl(CaM1)proteins,were isolated from the cDNA library of amphioxus Branchiostoma belcheri tsingtauense.There are only two nucleotide differences between them,producing one amino acid difference betweenCaM1a and CaM1b.Comparison of the amino acid sequence of CaM1 reveals that the B.belcheri tsingtauenseCaM1a is identical with CaM1 proteins of B.floridae and B.lanceolatum,Drosophila melanogaster CaM,ascidian Halocynthia roretzi CaMA and mollusk Aplysia californica CaM,and CaM1b differs only at oneposition(138,Asn to Asp).The phylogenetic analysis indicates that the CaM1 in all three amphioxus speciesappears to encode the conventional CaM and CaM2 might be derived from gene duplication of CAM1.Southern blot suggests that there are two copies of CaM1 in the genome of B.belcheri tsingtauense.Northernblot and in situ hybridization analysis shows the presence of two CaM1 mRNA transcripts with variousexpression levels in different adult tissues and embryonic stages in amphioxus B.belcheri tsingtauense.Theevolution and diversity of metazoan CaM mRNA transcripts are also discussed.