Influences of 4-nonylphenol on doublesex- and mab-3-related transcription factor 1 gene expression and vitellogenin mRNA induction of adult rare minnow (Gobiocypris rarus).

The mab-3 of Caenorhabditis elegans and doublesex of Drosophila are two sex-determining genes that are found to have only a common DNA binding motif called a doublesex and mab-3 (DM) domain among phyla. The DM domain regulates some aspects of sexual development such as yolk protein synthesis. In the present study, by using DM degenerate primers' 13 sequences of doublesex and mab-3-related transcription factor (dmrt), genes were cloned from genomic DNA of rare minnow (Gobiocypris rarus) and expression of dmrt1 was detected only in testis of adult males. In addition, partial sequences of vitellogenin (vtg) and beta-actin genes as comparative expression of genes were cloned from the female liver by degenerate primers based on conserved regions. The vtg mRNA in male liver was induced significantly in concentrations higher than 2 microg/L treatments, although adult rare minnow were exposed to nominal concentrations of 2, 10, 50, 250, and 1,250 microg/L 4-nonylphenol (4-NP) for 21 d. The dmrt1 mRNA level was significantly downregulated in a dose-dependent manner in all exposure groups of males. Moreover, other toxic endpoints, including growth, gonadosomatic index, hepatosomatic index, and histopathology, were determined. However, significant effects were observed only at higher exposure concentrations. Therefore, sex-specific genes such as dmrt1 can be used as a more sensitive biomarker for 4-NP and for discovering molecular mechanisms underlying toxic response.