Cloning, characterization and cadmium inducibility of metallothionein in the testes of the mudskipper Boleophthalmus pectinirostris

• We identified metallothionein (MT) complete cDNA sequence in mudskipper.
• Tissue expression of MT mRNA was analyzed by RT-PCR.
• Distribution pattern of MT in testes was analyzed by immunohistochemistry method.
• Cd-induced injury in testes and response of MT mRNA were observed.
• MTs play an important role in spermatogenesis and testes protection in B. pectinirostris.

Metallothioneins (MTs) are cysteine-rich, low molecular weight, and heavy metal-binding protein molecules. MT participates in metallic homeostasis and detoxification in living animals due to its abundant cysteine. In order to investigate the functions of MT during spermiogenesis in the mudskipper (Boleophthalmus pectinirostris), we identified the MT complete which contains: an 83 bp 5′ untranslated region, a 110 bp 3′ untranslated region, and a 183 bp open reading frame. The protein alignment between MT sequences of other species shows a high similarity and a strong identity in cysteine residues vital for the metal-binding affinity of MT. The localizations of MT were mainly in the cytoplasm of germinal cells, indicating a role in spermatogenesis and testis protection. After the cadmium (Cd) exposure, the testis presents abnormal morphology and MT mRNA expression, both of which indicate a sensitive response of testis MT to Cd. Therefore, we suggest that MTs play an important role in spermatogenesis and testes protection against Cd toxicity in B. pectinirostris.