Elevated Expression of follistatin Gene in the Pituitaries of Allotriploid Crucian Carp

As a paracrine factor, Follistatin (Fst) plays an important role in regulating biosynthesis and release of pituitary gonadotropin (GTH), gonadal development, and ovulation cycle. In this study, full-length complementary DNAs (cDNAs) of the follistatin gene in diploid red crucian carp, Carassius auratus red var., allotriploid crucian carp, and allotetraploid hybrids were obtained. Our data showed that the cDNAs of follistatin of all three fish encoded 322 amino acids. Referring to the structural characteristics of Fst in other species, we found that the Fst protein of these three fish had four domains, respectively. Reverse transcriptase polymerase chain reaction (PCR) indicated that the follistatin gene was widely expressed in all tested tissues, except spleens, in these three fish. Real-time quantitative PCR analysis of different seasonal profiles showed that allotriploids had significantly higher expression of follistatin messenger RNA in pituitaries during both the prespawning and spawning periods. These results suggest that the elevated expression of the follistatin gene in the pituitaries of allotriploids might lead to sterility of allotriploids by blocking the inhibitory effect of activin on luteinizing hormone subunit. Furthermore, the results may improve our understanding of reproduction characteristics in triploids, which benefits polyploidy breeding.