Bix1, a direct target of Xenopus T-box genes, causes formation of ventral mesoderm and endoderm

Development ◽  
1998 ◽  
Vol 125 (20) ◽  
pp. 3997-4006 ◽  
Author(s):  
M. Tada ◽  
E.S. Casey ◽  
L. Fairclough ◽  
J.C. Smith
Keyword(s):  
Target Genes ◽  
Regulatory Region ◽  
Homeobox Gene ◽  
Subtractive Hybridization ◽  
Vertebrate Development ◽  
Transcription Activator ◽  
T Box ◽  
Endodermal Differentiation ◽  
Inducing Factors ◽  
Mesoderm Inducing Factors

Brachyury, a member of the T-box gene family, is required for posterior mesoderm and notochord differentiation in vertebrate development, and mis-expression of Xenopus Brachyury causes ectopic mesoderm formation. Brachyury is a transcription activator, and its ability to activate transcription is essential for its biological function, but Brachyury target genes have proved difficult to identify. Here we employ a hormone-inducible Brachyury construct and subtractive hybridization to search for such targets. Using this approach we have isolated Bix1, a homeobox gene expressed both in the marginal zone of Xenopus and in the vegetal hemisphere. Expression of Bix1 is induced in an immediate-early fashion by mesoderm-inducing factors such as activin as well as by the products of the T-box genes Xbra and VegT (also known as Antipodean, Brat and Xombi). Activation of Bix1 in response to Xbra is direct in the sense that it does not require protein synthesis, and both Xbra and VegT activate expression of a reporter gene driven by the Bix 5′ regulatory region, which contains an Xbra/VegT binding site. Mis-expression of low levels of Bix1 causes formation of ventral mesoderm, while high levels induce endodermal differentiation. These results suggest that Bix1 acts downstream of both VegT and Xbra to induce formation of mesoderm and endoderm.

Bix4 is activated directly by VegT and mediates endoderm formation in Xenopus development

Development ◽  
1999 ◽  
Vol 126 (19) ◽  
pp. 4193-4200 ◽  
Author(s):  
E.S. Casey ◽  
M. Tada ◽  
L. Fairclough ◽  
C.C. Wylie ◽  
J. Heasman ◽  
...  
Keyword(s):  
Binding Sites ◽  
Essential Role ◽  
Regulatory Region ◽  
Reporter Genes ◽  
Transcription Activator ◽  
T Box ◽  
Xenopus Embryos ◽  
Vegetal Pole ◽  
Endodermal Differentiation ◽  
Necessary And Sufficient

The maternal T-box gene VegT, whose transcripts are restricted to the vegetal hemisphere of the Xenopus embryo, plays an essential role in early development. Depletion of maternal VegT transcripts causes embryos to develop with no endoderm, while vegetal blastomeres lose the ability to induce mesoderm (Zhang, J., Houston, D. W., King, M. L., Payne, C., Wylie, C. and Heasman, J. (1998) Cell 94, 515–524). The targets of VegT, a transcription activator, must therefore include genes involved both in the specification of endoderm and in the production of mesoderm-inducing signals. We recently reported that the upstream regulatory region of the homeobox-containing gene Bix4 contains T-box binding sites. Here we show that expression of Bix4 requires maternal VegT and that two T-box binding sites are necessary and sufficient for mesodermal and endodermal expression of reporter genes driven by the Bix4 promoter in transgenic Xenopus embryos. Remarkably, a single T-box binding site is able to act as a mesoderm-specific enhancer when placed upstream of a minimal promoter. Finally, we show that Bix4 rescues the formation of endodermal markers in embryos in which VegT transcripts have been ablated but does not restore the ability of vegetal pole blastomeres to induce mesoderm. These results demonstrate that Bix4 acts directly downstream of VegT to specify endodermal differentiation in Xenopus embryos.

The T-box transcription factor Brachyury regulates expression of eFGF through binding to a non-palindromic response element

Development ◽  
1998 ◽  
Vol 125 (19) ◽  
pp. 3887-3894 ◽  
Author(s):  
E.S. Casey ◽  
M.A. O'Reilly ◽  
F.L. Conlon ◽  
J.C. Smith
Keyword(s):  
Transcription Factor ◽  
Site Selection ◽  
Target Genes ◽  
Biological Function ◽  
Start Site ◽  
Palindromic Sequence ◽  
Vertebrate Development ◽  
Transcription Start ◽  
T Box ◽  
Human And Mouse

Brachyury is a member of the T-box gene family and is required for formation of posterior mesoderm and notochord during vertebrate development. The ability of Brachyury to activate transcription is essential for its biological function, but nothing is known about its target genes. Here we demonstrate that Xenopus Brachyury directly regulates expression of eFGF by binding to an element positioned approximately 1 kb upstream of the eFGF transcription start site. This site comprises half of the palindromic sequence previously identified by binding site selection and is also present in the promoters of the human and mouse homologues of eFGF.

Analysis of competence and of Brachyury autoinduction by use of hormone-inducible Xbra

Development ◽  
1997 ◽  
Vol 124 (11) ◽  
pp. 2225-2234 ◽  
Author(s):  
M. Tada ◽  
M.A. O'Reilly ◽  
J.C. Smith
Keyword(s):  
Glucocorticoid Receptor ◽  
Target Genes ◽  
Early Embryo ◽  
Fate Map ◽  
Animal Pole ◽  
Reading Frame ◽  
Xenopus Development ◽  
Series Of Experiments ◽  
Inducing Factors ◽  
Mesoderm Inducing Factors

Analysis of gene function in Xenopus development frequently involves over-expression experiments, in which RNA encoding the protein of interest is microinjected into the early embryo. By taking advantage of the fate map of Xenopus, it is possible to direct expression of the protein to particular regions of the embryo, but it has not been possible to exert control over the timing of expression; the protein is translated immediately after injection. To overcome this problem in our analysis of the role of Brachyury in Xenopus development, we have, like Kolm and Sive (1995; Dev. Biol. 171, 267–272), explored the use of hormone-inducible constructs. Animal pole regions derived from embryos expressing a fusion protein (Xbra-GR) in which the Xbra open reading frame is fused to the ligand-binding domain of the human glucocorticoid receptor develop as atypical epidermis, presumably because Xbra is sequestered by the heat-shock apparatus of the cell. Addition of dexamethasone, which binds to the glucocorticoid receptor and releases Xbra, causes formation of mesoderm. We have used this approach to investigate the competence of animal pole explants to respond to Xbra-GR, and have found that competence persists until late gastrula stages, even though by this time animal caps have lost the ability to respond to mesoderm-inducing factors such as activin and FGF. In a second series of experiments, we demonstrate that Xbra is capable of inducing its own expression, but that this auto-induction requires intercellular signals and FGF signalling. Finally, we suggest that the use of inducible constructs may assist in the search for target genes of Brachyury.

A functional homologue of goosecoid in Drosophila

Development ◽  
1996 ◽  
Vol 122 (5) ◽  
pp. 1641-1650 ◽  
Author(s):  
A. Goriely ◽  
M. Stella ◽  
C. Coffinier ◽  
D. Kessler ◽  
C. Mailhos ◽  
...  
Keyword(s):  
Protein Sequence ◽  
Target Genes ◽  
Homeobox Gene ◽  
Functional Domain ◽  
Vertebrate Development ◽  
Cellular Processes ◽  
Protein Sequence Homology ◽  
Definition Of ◽  
The Right ◽  
Shed Light

We have cloned a Drosophila homologue (D-gsc) of the vertebrate homeobox gene goosecoid (gsc). In the Gsc proteins, the pressure for conservation has been imposed on the homeodomain, the functional domain of the protein: sequence homology is limited to the homeodomain (78% identity) and to a short stretch of 7 aminoacids also found in other homeoproteins such as Engrailed. Despite this weak homology, D-gsc is able to mimic gsc function in a Xenopus assay, as shown by its ability to rescue the axis development of a UV-irradiated embryo. Moreover, our data suggest that the position of insect and vertebrate gsc homologues within a regulatory network has also been conserved: D-gsc expression is controlled by decapentaplegic, orthodenticle, sloppy-paired and tailless whose homologues control gsc expression (for BMP4 and Otx-2), or are expressed at the right time and the right place (for XFKH1/Pintallavis and Tlx) to be interacting with gsc during vertebrate development. However, the pattern of D-gsc expression in ectodermal cells of the nervous system and foregut cannot easily be reconciled with that of vertebrate gsc mesodermal expression, suggesting that its precise developmental function might have diverged. Still, this comparison of domains of expression and functions among Gsc proteins could shed light on a common origin of gut formation and/or on basic cellular processes. The identification of gsc target genes and/or other genes involved in similar developmental processes will allow the definition of the precise phylogenetic relationship among Gsc proteins.

scholarly journals Quantitative comparison of mesoderm inducing factors in xenopus

1989 ◽  
Vol 27 ◽  
pp. 53
Author(s):  
J.B.A. Green ◽  
G. Howes ◽  
M. Yaqoob ◽  
J. Cooke ◽  
J.C. Smith
Keyword(s):  
Quantitative Comparison ◽  
Inducing Factors ◽  
Mesoderm Inducing Factors

T-Box Genes in Vertebrate Development

2005 ◽  
Vol 39 (1) ◽  
pp. 219-239 ◽  
Author(s):  
L.A. Naiche ◽  
Zachary Harrelson ◽  
Robert G. Kelly ◽  
Virginia E. Papaioannou
Keyword(s):  
Vertebrate Development ◽  
T Box

scholarly journals TAL Effector Repertoires of Strains of Xanthomonas phaseoli pv. manihotis in Commercial Cassava Crops Reveal High Diversity at the Country Scale

2021 ◽  
Vol 9 (2) ◽  
pp. 315
Author(s):  
Carlos A. Zárate-Chaves ◽  
Daniela Osorio-Rodríguez ◽  
Rubén E. Mora ◽  
Álvaro L. Pérez-Quintero ◽  
Alexis Dereeper ◽  
...  
Keyword(s):  
Target Genes ◽  
Susceptibility Gene ◽  
Rflp Analysis ◽  
Transcription Activator ◽  
Cassava Bacterial Blight ◽  
Functional Convergence ◽  
Neutral Genetic Diversity ◽  
Functional Variant ◽  
Novel Variants ◽  
Host Metabolism

Transcription activator-like effectors (TALEs) play a significant role for pathogenesis in several xanthomonad pathosystems. Xanthomonas phaseoli pv. manihotis (Xpm), the causal agent of Cassava Bacterial Blight (CBB), uses TALEs to manipulate host metabolism. Information about Xpm TALEs and their target genes in cassava is scarce, but has been growing in the last few years. We aimed to characterize the TALE diversity in Colombian strains of Xpm and to screen for TALE-targeted gene candidates. We selected eighteen Xpm strains based on neutral genetic diversity at a country scale to depict the TALE diversity among isolates from cassava productive regions. RFLP analysis showed that Xpm strains carry TALomes with a bimodal size distribution, and affinity-based clustering of the sequenced TALEs condensed this variability mainly into five clusters. We report on the identification of 13 novel variants of TALEs in Xpm, as well as a functional variant with 22 repeats that activates the susceptibility gene MeSWEET10a, a previously reported target of TAL20Xam668. Transcriptomics and EBE prediction analyses resulted in the selection of several TALE-targeted candidate genes and two potential cases of functional convergence. This study provides new bases for assessing novel potential TALE targets in the Xpm–cassava interaction, which could be important factors that define the fate of the infection.

Retinoic acid and chick limb bud development

Development ◽  
1991 ◽  
Vol 113 (Supplement_1) ◽  
pp. 113-121 ◽  
Author(s):  
C. Tickle
Keyword(s):  
Retinoic Acid ◽  
Target Genes ◽  
Homeobox Gene ◽  
Experimental System ◽  
Shoulder Girdle ◽  
Limb Bud ◽  
Local Concentration ◽  
Anterior Position ◽  
Mesenchyme Cells ◽  
Vitamin A Derivative

The chick limb bud is a powerful experimental system in which to study pattern formation in vertebrate embryos. Exogenously applied retinoic acid, a vitamin A derivative, can bring about changes in pattern and, on several grounds, is a good candidate for an endogenous morphogen. As such, the local concentration of retinoic acid might provide cells with information about their position in relation to one axis of the limb. Alternatively, retinoic acid may be part of a more complex signalling system. Homeobox genes are possible target genes for regulation by retinoic acid in the limb. In particular, one homeobox gene, XlHbox 1 is expressed locally in the mesenchyme of vertebrate forelimbs and might code for an anterior position. When the pattern of the chick wing is changed by retinoic acid or by grafts of signalling tissue such that anterior cells now form posterior structures, the domain of XlHbox 1 expression expands rather than contracts. The expansion of XlHbox 1 expression correlates with shoulder girdle abnormalities. Retinoic acid application leads to visible changes in bud shape and this allows dissection of the way in which patterning is co-ordinated with morphogenesis. Results of recombination experiments and studies of changes in the apical ridge and proliferation in the mesenchyme suggest the following scheme: retinoic acid is involved in specification of position of mesenchyme cells; this specification determines their local interaction with the ridge that controls ridge morphology; the thickened apical ridge permits local proliferation in the underlying mesenchyme. The recent advances in molecular biology that permit analysis of the expression of various interesting genes in developing limbs hold out the promise that further investigation may soon allow a complete account of the patterning process in one part of the vertebrate embryo.

Mechanism of anteroposterior axis specification in vertebrates. Lessons from the amphibians

Development ◽  
1992 ◽  
Vol 114 (2) ◽  
pp. 285-302 ◽  
Author(s):  
J.M. Slack ◽  
D. Tannahill
Keyword(s):  
Molecular Markers ◽  
Expression Patterns ◽  
Signal Transduction Pathway ◽  
Homeobox Gene ◽  
Neural Induction ◽  
High Sensitivity ◽  
Neural Plate ◽  
Mesoderm Induction ◽  
Inducing Factors ◽  
Almost All

Interest in the problem of anteroposterior specification has quickened because of our near understanding of the mechanism in Drosophila and because of the homology of Antennapedia-like homeobox gene expression patterns in Drosophila and vertebrates. But vertebrates differ from Drosophila because of morphogenetic movements and interactions between tissue layers, both intimately associated with anteroposterior specification. The purpose of this article is to review classical findings and to enquire how far these have been confirmed, refuted or extended by modern work. The “pre-molecular” work suggests that there are several steps to the process: (i) Formation of anteroposterior pattern in mesoderm during gastrulation with posterior dominance. (ii) Regional specific induction of ectoderm to form neural plate. (iii) Reciprocal interactions from neural plate to mesoderm. (iv) Interactions within neural plate with posterior dominance. Unfortunately, almost all the observable markers are in the CNS rather than in the mesoderm where the initial specification is thought to occur. This has meant that the specification of the mesoderm has been assayed indirectly by transplantation methods such as the Einsteckung. New molecular markers now supplement morphological ones but they are still mainly in the CNS and not the mesoderm. A particular interest attaches to the genes of the Antp-like HOX clusters since these may not only be markers but actual coding factors for anteroposterior levels. We have a new understanding of mesoderm induction based on the discovery of activins and fibroblast growth factors (FGFs) as candidate inducing factors. These factors have later consequences for anteroposterior pattern with activin tending to induce anterior, and FGF posterior structures. Recent work on neural induction has implicated cAMP and protein kinase C (PKC) as elements of the signal transduction pathway and has provided new evidence for the importance of tangential neural induction. The regional specificity of neural induction has been reinvestigated using molecular markers and provides conclusions rather similar to the classical work. Defects in the axial pattern may be produced by retinoic acid but it remains unclear whether its effects are truly coordinate ones or are concentrated in certain regions of high sensitivity. In general the molecular studies have supported and reinforced the “pre-molecular ones”. Important questions still remain: (i) How much pattern is there in the mesoderm (how many states?) (ii) How is this pattern generated by the invaginating organizer? (iii) Is there one-to-one transmission of codings to the neural plate? (iv) What is the nature of the interactions within the neural plate? (v) Are the HOX cluster genes really the anteroposterior codings?

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