Sequence and expression of androgen receptor and estrogen receptor gene in the sex types of protogynous wrasse, Halichoeres trimaculatus.

Sex steroid hormones play important roles in sex change and behavior of wrasses. Their actions are considered to be mediated through the nuclear hormone receptors. In this study, to elucidate the roles of estrogen receptor (ER) and androgen receptor (AR) in the reproduction of the protogynous wrasse, Halichoeres trimaculatus, AR and ER genes were partially cloned using 5'- and 3'-RACE and their transcript levels in the gonads and the brain were measured by competitive RT-PCR. The amino acid sequence (563 a.a) deduced from 5' truncated cDNA encoding wrasse AR shows about 81%, 69%, 66%, 64%, and 58% identity with those of red seabream (Chrysophrys major) androgen receptor subtype, AR1, and rainbow trout (Oncorhynchus mykiss) ARalpha, ARbeta, Japanese eel (Anguilla japonica) ARalpha, and ARbeta, respectively. The amino acid sequence (458 a.a) deduced from 5(') truncated cDNA encoding wrasse ER shows about 81%, 79%, 73%, 66%, and 63% identity with those of red seabream estrogen receptor subtype, ERalpha, Atlantic croaker (Micropogonias undulatus) ERalpha, tilapia (Oreochromis niloticus) ERalpha, rainbow trout ERalpha, and catfish (Ictalurus punctatus) ERalpha, respectively. Among the various tissues tested, AR and ER mRNAs were highly expressed in the gonads and brains. When the transcript levels of ER were measured in the gonads and the brains of females (F), initial phase male (IP), and terminal phase male (TP), no significant changes in the gene expression were observed. The transcript levels of AR in the gonads did not change among different sex types, while those in the brains of TP were higher than F and IP. These results suggest that higher expression of AR in the brains of TP is strongly correlated with behavioral change.