DMRT genes were first identified as transcription factors related to sex determination and sex differentiation, but as more and more different DMRT genes were identified from different species, DMRT genes obviously formed a gene family. Despite mammalian DMRT8, all those DMRT genes share a common feature of having a highly conserved DM domain, which has been shown to be responsible for their ability to binding DNA. But when the characters of different DMRT genes were well depicted gradually, we found that not all DMRT genes were involved in sex differentiation. So DMRT genes are not only conservative but also changeable to adapt to changing requirements. Thus it will be interesting to describe the existing DMRT genes in different species and to find and characterize new members of DMRT gene family.
We first cloned the full-length cDNAs of DMRT1 gene from grouper, which is protogynous hermaphrodite and sex reversal species. Through analyzing its gene structure and expression profile, we found it has two major differences from other DMRT1 homologues. First, no introns were found in the ORF of grouper DMRT1 gene, and the second, this gene was strictly expressed in spermatogenic cells during spermatogenesis. So we postulate the intronless DMRT1 that is able to undergo rapid transcriptional turnover might be a significant gene for stimulating spermatogenesis in the protogynous hermaphroditic gonad. At the same time, phylogenetic analysis and substitution estimation revealed a closer relationship that the grouper DMRT1 is most closely related to the homologues from bream, pejerrey, tilapia, rice field eel, and wrasse, although these fishes are distantly related species from the evolutionary and taxonomic points. Interestingly, sex reversal and environmental sex determination have been commonly reported in these fish species.
We also analyzed a fish specific new duplicated version of terra gene in crucian carp and zebrafish, and found that although this gene play essential roles during embryo development but unlike the orthologues of other genes, which are mostly conserved across species due to the strong purifying selective pressure on them, we observed that not only DMRT2b genes diverge from terra homologues functionally but also different DMRT2b homologues have experienced obvious functional divergence. And we also verified this divergence is not only due to the changing of their biochemical properties but also may be caused by changing of expression profiles and the molecular interactive environment. Accordingly we give a clear conception about the future work about this gene.