A sequence of progesterone receptor homologue in freshwater crocodile (Crocodylus siamensis)

A homologue to the progesterone receptor mRNA in freshwater crocodiles (Cro codylus siamensis), encoding 1039 nucleotides, was established by reverse t ranscriptase-polymerase chain reaction. The cDNA fragment, amplified and se quenced from oviduct tissue, was found to contain seven exons which encoded a deduced polypeptide of 346 amino acids in length with a high nucleotide and amino acid identity to known progesterone receptor sequences in other a nimals. Comparison of the crocodile cDNA fragment and the chicken progester one receptor gene indicated the presence of DNA- and steroid-binding domain s, including the hinge region. In addition, young freshwater crocodiles sho wed a sex-specific expression of this gene in laryngeal muscles recognized by Northern blot analysis. The cDNA probes were biotin-labelled and mapped by FISH to a subtelomeric region of the p-arm of the longest chromosome (pu tative chromosome 1). This is a contribution to a new approach towards unde rstanding the molecular mechanisms of temperature-dependent sex determinati on.