Cloning, characterization and expression of tyrosinase-like gene in amphioxus Branchiostoma japonicum

Prophenoloxidase (tyrosinase) widely distributed in invertebrates and vertebrates, and plays a crucial role in the innate immune. In the present study, the full-length cDNA of a tyrosinase-like (designated AmphiTYR) was cloned from amphioxus Branchiostoma japonicum by PCR techniques. The full-length cDNA of AmphiTYR is 2314 bp, and its predicted open-reading frame codes for a protein of 544 amino acids with a predicted molecular mass of approximately 60.9 kDa and an isoelectric point of 5.65. It has a conserved putative copper-binding domain with six histidines in tyrosinase proteins. Six potential N-linked glycosylation sites and 14 conserved cysteine residues were also predicted to be present in B. japonicum tyrosinase. Homology analysis revealed that AmphiTYR was higher similar to vertebrates tyrosinases (32.5–40.5%) than to invertebrates phenoloxidase (6.4–25.4%). In the adult, AmphiTYR mRNA was expressed in the muscle, epidermis, notochord, ovary, hepatic caecum, pharynx and gill, but not in the neural tube, intestines and testis. During the different development stages from unfertilized egg to larvae of amphioxus, AmphiTYR expressed during all the amphioxus development. These results indicated that AmphiTYR gene not only play a pivotal role in innate immune but also play an important role during embryonic development of cephalochordate amphioxus.