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Functional evolution of the Ultrabithorax protein
1Howard Hughes Medical Institute, Laboratory of Molecular Biology, University of Wisconsin, 1525 Linden Drive, Madison, WI 53706, USA.
Summary
Functional changes in Ultrabithorax (Ubx) proteins contributed to insect evolution. While insect and onychophoran Ubx proteins are similar, the onychophoran version lacks key functions, suggesting evolutionary adaptations in cofactors or modifiers.
Area of Science:
- Evolutionary developmental biology
- Comparative genomics
- Animal body plan evolution
Background:
- Hox genes are crucial for animal body plan diversity.
- Regulatory and functional changes in Hox proteins may drive morphological evolution.
Purpose of the Study:
- Compare in vivo functions of Ultrabithorax (Ubx) proteins from Drosophila melanogaster (insect) and an onychophoran.
- Investigate functional divergence of Ubx proteins over 540 million years of evolution.
Main Methods:
- Expressed orthologous Ultrabithorax (Ubx) proteins from Drosophila and an onychophoran in Drosophila.
- Assessed gain-of-function tissue transformations and target gene activation/repression.
Main Results:
- Both Ubx proteins induced similar tissue transformations and affected many common target genes.
- Onychophoran Ubx (OUbx) did not transform embryonic ectoderm or repress the Distal-less gene.
- Functional divergence is attributed to sequence changes outside the homeodomain.
Conclusions:
- Ubx protein function has diverged since the onychophoran-insect split.
- Onyx may have gained new cofactors or activity modifiers for Ubx function in the insect lineage.