Abstract
ABSTRACTSome DMRT family genes including arthropod dsx, nematode mab-3, and vertebrate dmrt1 are involved in sex determination and/or differentiation in bilaterian animals. Although there have been some reports about evolutionary analyses of the family by using its phylogenetic trees, it is still undecided as to whether these three sex determination-related genes share orthologous relationships or not. To clarify this question, we analyzed evolutional relationships among the family members in various bilaterians by using not only phylogenetic tree analysis, but also synteny analysis. We found that only four genes, dmrt2a/2b, dmrt3, dmrt4/5 and dmrt93B were commonly present in invertebrate bilateria. The syntenies of dmrt2a/2b-dmrt3 and dmrt4/5-dmrt93B are conserved before and after two rounds of whole genome duplication in the ancestral vertebrate. Importantly, this indicates that dmrt1 must have appeared in the common vertebrate ancestor. In addition, dmrt1, dsx, or mab-3 formed each different cluster at a distance in our phylogenetic tree. From these findings, we concluded that the three sex determination-related genes, dmrt1, dsx, and mab-3 have no orthologous relationships, and suggested independent evolution for sex determination and differentiation in the DMRT gene family. Our results may supply clues about why sex-determining systems have diverged during animal evolution.
Highlights
The doublesex and mab-3 related transcription factor (DMRT) family is well-conserved in bilaterian animals and is characterized by a DNA-binding region called the DM domain (Matson and Zarkower, 2012)
We found that four DMRT genes, dmrt2a/2b, dmrt3, dmrt4/5 and dmrt93B were commonly present in invertebrate bilateria
These results suggested that the three sex determination-related genes, dmrt1, dsx and mab-3 might emerge independently in each taxon and obtain new functions for sex determination and/or primary sex differentiation
Summary
The doublesex and mab-3 related transcription factor (DMRT) family is well-conserved in bilaterian animals and is characterized by a DNA-binding region called the DM domain (Matson and Zarkower, 2012). Only the three types of the DMRT family genes – that is, dmrt1 homologs, dsx and mab-3 – are known to function in sex determination and/or somatic sex differentiation to date. Our recent report indicated that the ancestral gene of vertebrate dmrt1 might have emerged not for sex determination but for germ-cell development (Mawaribuchi et al, 2017a), suggesting that dmrt1 might not be a functional ortholog of dsx and mab-3.
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