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Co‐orthology of P ax4 and P ax6 to the fly eyeless gene: molecular phylogenetic, comparative genomic, and embryological analyses
Author(s) -
Manousaki Tereza,
Feiner Nathalie,
Begemann Gerrit,
Meyer Axel,
Kuraku Shigehiro
Publication year - 2011
Publication title -
evolution and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.651
H-Index - 78
eISSN - 1525-142X
pISSN - 1520-541X
DOI - 10.1111/j.1525-142x.2011.00502.x
Subject(s) - biology , gene duplication , synteny , genetics , gene , vertebrate , phylogenetic tree , evolutionary biology , genome , phylogenetics , context (archaeology) , pax6 , gene family , paleontology , transcription factor
SUMMARY The functional equivalence of P ax6/eyeless genes across distantly related animal phyla has been one of central findings on which evo‐devo studies is based. In this study, we show that P ax4 , in addition to P ax6 , is a vertebrate ortholog of the fly eyeless gene (and its duplicate, twin of eyeless [ toy ] gene, unique to I nsecta). Molecular phylogenetic trees published to date placed the P ax4 gene outside the P ax6 / eyeless subgroup as if the P ax4 gene originated from a gene duplication before the origin of bilaterians. However, P ax4 genes had only been reported for mammals. Our molecular phylogenetic analysis, including previously unidentified teleost fish pax4 genes, equally supported two scenarios: one with the P ax4 – P ax6 duplication early in vertebrate evolution and the other with this duplication before the bilaterian radiation. We then investigated gene compositions in the genomic regions containing P ax4 and P ax6 , and identified (1) conserved synteny between these two regions, suggesting that the P ax4 – P ax6 split was caused by a large‐scale duplication and (2) its timing within early vertebrate evolution based on the duplication timing of the members of neighboring gene families. Our results are consistent with the so‐called two‐round genome duplications in early vertebrates. Overall, the P ax6 / eyeless ortholog is merely part of a 2:2 orthology relationship between vertebrates (with P ax4 and P ax6 ) and the fly (with eyeless and toy ). In this context, evolution of transcriptional regulation associated with the P ax4 – P ax6 split is also discussed in light of the zebrafish pax4 expression pattern that is analyzed here for the first time.