scholarly journals Determination of floral organ identity by Arabidopsis MADS domain homeotic proteins AP1, AP3, PI, and AG is independent of their DNA-binding specificity.

1997 ◽  
Vol 8 (7) ◽  
pp. 1243-1259 ◽  
Author(s):  
J L Riechmann ◽  
E M Meyerowitz
Keyword(s):  
Dna Binding ◽  
Ectopic Expression ◽  
Binding Specificity ◽  
Floral Organ ◽  
Floral Organ Identity ◽  
Chimeric Genes ◽  
Amino Terminal ◽  
Dna Binding Specificity ◽  
Organ Identity

The MADS domain homeotic proteins APETALA1 (AP1), APETALA3 (AP3), PISTILLATA (PI), and AGAMOUS (AG) combinatorially specify the identity of Arabidopsis floral organs. AP1/AP1, AG/AG, and AP3/PI dimers bind to similar CArG box sequences; thus, differences in DNA-binding specificity among these proteins do not seem to be the origin of their distinct organ identity properties. To assess the overall contribution that specific DNA binding could make to their biological specificity, we have generated chimeric genes in which the amino-terminal half of the MADS domain of AP1, AP3, PI, and AG was substituted by the corresponding sequences of human SRF and MEF2A proteins. In vitro DNA-binding assays reveal that the chimeric proteins acquired the respective, and distinct, DNA-binding specificity of SRF or MEF2A. However, ectopic expression of the chimeric genes reproduces the dominant gain-of-function phenotypes exhibited by plants ectopically expressing the corresponding Arabidopsis wild-type genes. In addition, both the SRF and MEF2 chimeric genes can complement the pertinent ap1-1, ap3-3, pi-1, or ag-3 mutations to a degree similar to that of AP1, AP3, PI, and AG when expressed under the control of the same promoter. These results indicate that determination of floral organ identity by the MADS domain homeotic proteins AP1, AP3, PI, and AG is independent of their DNA-binding specificity. In addition, the DNA-binding experiments show that either one of the two MADS domains of a dimer can be sufficient to confer a particular DNA-binding specificity to the complex and that sequences outside the amino-terminal basic region of the MADS domain can, in some cases, contribute to the DNA-binding specificity of the proteins.

Alteration of floral organ identity in rice through ectopic expression of OsMADS16

Planta ◽  
2003 ◽  
Vol 217 (6) ◽  
pp. 904-911 ◽  
Author(s):  
Sichul Lee ◽  
Jong-Seong Jeon ◽  
Kyungsook An ◽  
Yong-Hwan Moon ◽  
Sanghee Lee ◽  
...  
Keyword(s):  
Ectopic Expression ◽  
Floral Organ ◽  
Floral Organ Identity ◽  
Organ Identity

scholarly journals DNA Immunoprecipitation (DIP) for the Determination of DNA-Binding Specificity

2008 ◽  
Vol 2008 (4) ◽  
pp. pdb.prot4972-pdb.prot4972 ◽  
Author(s):  
A. J. Gossett ◽  
J. D. Lieb
Keyword(s):  
Dna Binding ◽  
Binding Specificity ◽  
Dna Binding Specificity

scholarly journals SUPERMAN prevents stamen formation and promotes stem cell termination in the fourth whorl of the Arabidopsis flower

2017 ◽  
Author(s):  
Nathanaël Prunet ◽  
Weibing Yang ◽  
Pradeep Das ◽  
Elliot M. Meyerowitz ◽  
Thomas P. Jack
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Floral Organ ◽  
Genetic Networks ◽  
Confocal Imaging ◽  
Identity Change ◽  
Floral Organ Identity ◽  
Organ Identity

SummaryThe molecular and genetic networks underlying the determination of floral organ identity are well studied, but much less is known about how the flower is partitioned into four developmentally distinct whorls. The SUPERMAN gene is required for proper specification of the boundary between stamens in whorl 3 and carpels in whorl 4, as superman mutants exhibit supernumerary stamens but usually lack carpels. However, it has remained unclear whether extra stamens in superman mutants originate from an organ identity change in whorl 4 or the overproliferation of whorl 3. Using live confocal imaging, we show that the extra stamens in superman mutants arise from cells in whorl 4, which change their fate from female to male, while floral stem cells proliferate longer, allowing for the production of additional stamens.

The Arabidopsis nectary is an ABC-independent floral structure

Development ◽  
2001 ◽  
Vol 128 (22) ◽  
pp. 4657-4667 ◽  
Author(s):  
Stuart F. Baum ◽  
Yuval Eshed ◽  
John L. Bowman
Keyword(s):  
Ectopic Expression ◽  
Floral Organ ◽  
Floral Structure ◽  
Floral Organ Identity ◽  
Floral Organs ◽  
The Third ◽  
Multiple Factors ◽  
Organ Identity ◽  
Selector Genes ◽  
B Class Genes

In contrast to the conservation of floral organ order in angiosperm flowers, nectary glands can be found in various floral and extrafloral positions. Since in Arabidopsis, the nectary develops only at the base of stamens, its specification was assayed with regard to the floral homeotic ABC selector genes. We show that the nectary can form independently of any floral organ identity gene but is restricted to the ‘third whorl’ domain in the flower. This domain is, in part, specified redundantly by LEAFY and UNUSUAL FLORAL ORGANS. Even though nectary glands arise from cells previously expressing the B class genes, their proper development requires the down-regulation of B class gene activity. While CRABS CLAW is essential for nectary gland formation, its ectopic expression is not sufficient to induce ectopic nectary formation. We show that in Arabidopsis multiple factors act to restrict the nectary to the flower, and surprisingly, some of these factors are LEAFY and UNUSUAL FLORAL ORGANS.

scholarly journals Pbx modulation of Hox homeodomain amino-terminal arms establishes different DNA-binding specificities across the Hox locus.

1996 ◽  
Vol 16 (4) ◽  
pp. 1734-1745 ◽  
Author(s):  
C P Chang ◽  
L Brocchieri ◽  
W F Shen ◽  
C Largman ◽  
M L Cleary
Keyword(s):  
Dna Binding ◽  
Hox Genes ◽  
Binding Specificity ◽  
Hox Proteins ◽  
Amino Terminal ◽  
Cellular Assays ◽  
Dna Binding Specificity ◽  
Dna Binding Properties ◽  
Half Site

Pbx cofactors are implicated to play important roles in modulating the DNA-binding properties of heterologous homeodomain proteins, including class I Hox proteins. To assess how Pbx proteins influence Hox DNA-binding specificity, we used a binding-site selection approach to determine high-affinity target sites recognized by various Pbx-Hox homeoprotein complexes. Pbx-Hox heterodimers preferred to bind a bipartite sequence 5'-ATGATTNATNN-3' consisting of two adjacent half sites in which the Pbx component of the heterodimer contacted the 5' half (ATGAT) and the Hox component contacted the more variable 3' half (TNATNN). Binding sites matching the consensus were also obtained for Pbx1 complexed with HoxA10, which lacks a hexapeptide but requires a conserved tryptophan-containing motif for cooperativity with Pbx. Interactions with Pbx were found to play an essential role in modulating Hox homeodomain amino-terminal arm contact with DNA in the core of the Hox half site such that heterodimers of different compositions could distinguish single nucleotide alterations in the Hox half site both in vitro and in cellular assays measuring transactivation. When complexed with Pbx, Hox proteins B1 through B9 and A10 showed stepwise differences in their preferences for nucleotides in the Hox half site core (TTAT to TGAT, 5' to 3') that correlated with the locations of their respective genes in the Hox cluster. These observations demonstrate previously undetected DNA-binding specificity for the amino-terminal arm of the Hox homeodomain and suggest that different binding activities of Pbx-Hox complexes are at least part of the position-specific activities of the Hox genes.

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