Comparative studies on duplicated tdrd7 paralogs in teleosts: Molecular evolution caused neo-functionalization

Area of Science:

• Evolutionary biology
• Genomics
• Developmental biology

Background:

• The third-round whole genome duplication (3R-WGD) significantly impacted teleost evolution and diversification.
• TUDOR domain containing protein 7 (Tdrd7) is crucial in mammals, but its role in teleosts is understudied.

Purpose of the Study:

• To identify and characterize teleost Tdrd7 genes.
• To investigate the evolutionary origins and functional divergence of Tdrd7 paralogs in Japanese flounder (Paralichthys olivaceus).

Main Methods:

• Transcriptome analysis to identify tdrd7 genes.
• Phylogenetic, synteny, and genomic structure analyses.
• Bioinformatic mining of tdrd7 duplications in other species.
• Expression pattern analysis in adult tissues and embryos.
• Reporter gene assays (eGFP/DsRED) for germ cell visualization.

Main Results:

• Two tdrd7 genes, tdrd7a and tdrd7b, were identified and confirmed to originate from the 3R-WGD.
• Tdrd7a exhibits a higher molecular evolution rate and positive selection sites compared to tdrd7b.
• Tdrd7a displays gonad-specific expression and germ cell localization, enabling primordial germ cell visualization in zebrafish embryos.
• Tdrd7b lacks similar tissue and cell-type specificity.

Conclusions:

• The duplicated tdrd7 paralogs (tdrd7a and tdrd7b) in Japanese flounder have likely undergone neofunctionalization.
• These findings offer new insights into the evolution and functional diversification of teleost tdrd7 genes.