Molecular cloning of Pit-1 cDNA and genomic DNA of the domestic duck (Anas platyrhynchos)

The expression of unique isoform of pituitary transcription factor (Pit-1) is reported in the chicken and turkey. However, it is not well known whether this isoform is expressed in the other avian species. In the present study, complementary DNA (cDNA) and genomic DNA, of Pit-1 of domesticated duck, were cloned and sequenced. Duck Pit-1 alpha was found to have 93.3, and 92.4% sequence identity at the cDNA level to Pit-1 alpha of chicken and turkey, respectively. The predicted amino acid sequence had 96.7% similarity with a comparable region of Pit-1 alpha of both chicken and turkey. Based on the cDNA sequence, the genomic structure of the gene was characterized. The duck Pit-1 gene consisted of seven exons and six introns. Sequence analysis of the duck Pit-1 gene allowed for the design of a forward primer for amplification of Pit-1 gamma, which is synthesized from an alternative transcription initiation site in galliforms. Reverse transcription of total RNA followed by polymerase chain reaction successively amplified a 984 bp product of Pit-1 gamma cDNA, which encoded a peptide of 326 amino acids. These results suggest that the expression of Pit-1 isoform originates from a different site of transcription initiation, which is not unique to galliforms but is observed in other avian species including anseriforms.