Up-regulation of P450arom and down-regulation of Dmrt-1 genes in the temperature-dependent sex reversal from genetic males to phenotypic females in a salamander.

When larvae of the salamander Hynobius retardatus were reared at a high temperature (28 degrees C) during their thermosensitive period (TSP=15-30 days after hatching), all larvae developed to phenotypic females irrespective of their genetic sexes. Hynobius P450 aromatase (P450arom) and Dmrt-1 complementary DNAs were isolated and their expression patterns were analyzed by competitive and conventional reverse transcriptase-polymerase chain reaction. While the P450arom gene was expressed predominantly in the ovary, Dmrt-1 was expressed exclusively in the testis. When larvae were reared at the female-producing temperature (28 degrees C) during the TSP, a strong expression of the P450arom gene and a complete suppression of the Dmrt-1 gene were induced in all experimental larvae. Up-regulation of the P450arom gene and down-regulation of the Dmrt-1 gene even in genetic males constitute a part of the molecular biological cascade for the temperature-dependent sex reversal from genetic males to phenotypic females in this salamander.