Cloning and spatiotemporal expression analysis of Smad1/5 gene in the blood clam Tegillarca granosa

In order to explore the function of Smad1/5 during the process of the growth and development in Tegillarca granosa,Tg-Smad 1/5 was cloned by SMART RACE techniques.The full length cDNA of Tg-Smad1/5 was 2 424 bp,and its complete ORF (Open Reading Frame) was 1 386 bp encoding 462 amino acids.The homologous similarity between the clam and Pinctada fucata Smad5,Crassostrea gigas Smad5,Crepidula fornicate Smad1was 92.3%,91.2% and 80.4%,respectively.It shared more than 70% similarity with vertebrates.There were two conserved domains of Smads family,MH1 and MH2,which was especially similar to the vertebrates.All above suggested that,Smad1/5 is relatively conserved in the evolution,and has a similar function in various species.The results of 6 tissue-specific expression by real time PCR showed that Tg-Smad1/5 gene was expressed in all tissues,and the expression of foot was significantly higher than other tissues.The results of relative expression in 9 development stages revealed that the expression of Tg-Smad1/5 gene showed the highest expression in the eyebot larvae stage,which was significantly higher than other stages.And the expression decreased significantly from eyebot larvae stage to juvenile clams.The results showed that Tg-Smad1/5 had the similar molecular structure to the vertebrates,and the relative expression revealed differences in different tissues and development stages,which laid the theoretical foundation for further study on function and mechanism of Smad1/5 in molluscs.