Evolution of Brachyury proteins: identification of a novel regulatory domain conserved within Bilateria.
Orthologues of Brachyury, a subfamily of T-box transcription factors, specify distinct cell types in different metazoan phyla, suggesting that the function of these genes has changed through the course of evolution. To investigate this evolutionary process, we have compared the activities of Brachyury orthologues from all major phyla in a single cellular context, the pluripotent Xenopus laevis animal cap. In this assay, an ancestral function is revealed: most orthologues, including the Hydra protein, mimic the action of endogenous Xenopus Brachyury, in that they induce mesoderm but not endoderm. Orthologues from Drosophila and ascidians, however, display an additional derived property, represented in our assay by the induction of endoderm. Misexpression of chimeric versions of Brachyury reveals that the C-terminal half of the protein is important for the strength of the induced response but not for its specificity. In contrast, amino acids located within the T-domain and in a short N-terminal peptide are involved in restricting the activity of Brachyury proteins to induction of mesoderm and not endoderm. Possession of this N-terminal motif is correlated with early circumblastoporal expression of Brachyury orthologues. We propose that restriction of Brachyury activity by this motif plays a conserved role in the control of Bilaterian gastrulation.
Marcellini
Sylvain
S
Laboratoire de Génétique et Physiologie du Développement, IBDM, CNRS/INSERM/Universite de la Méditerranée/AP de Marseille, Parc Scientifique de Luminy, Case 907, F-13288, Marseille Cedex 9, France.
Technau
Ulrich
U
Smith
J C
JC
Lemaire
Patrick
P
D000595:Amino Acid Sequence; D000818:Animals; D017124:Conserved Sequence; D004475:Ectoderm / Q000502:physiology; D004625:Embryo, Nonmammalian; D004627:Embryonic Induction / Q000235:genetics; D019143:Evolution, Molecular; D005326:Fetal Proteins; D018507:Gene Expression Regulation, Developmental; D007448:Invertebrates / Q000235:genetics*; D008648:Mesoderm / Q000502:physiology; D008845:Microinjections; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D020825:T-Box Domain Proteins / Q000235:genetics / Q000502:physiology*; D014714:Vertebrates / Q000235:genetics*; D014982:Xenopus laevis / Q000196:embryology; D000098908:Brachyury Protein
D005326:Fetal Proteins; D011994:Recombinant Proteins; D020825:T-Box Domain Proteins; D000098908:Brachyury Protein