Riechmann, José Luis and Meyerowitz, Elliot M. (1997) Determination of floral organ identity by Arabidopsis MADS domain homeotic proteins AP1, AP3, PI, and AG is independent of their DNA-binding specificity. Molecular Biology of the Cell, 8 (7). pp. 1243-1259. ISSN 1059-1524 http://resolver.caltech.edu/CaltechAUTHORS:RIEmbc97
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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.
|Additional Information:||Copyright © 1997 by The American Society for Cell Biology. Submitted March 5, 1997; Accepted April 22, 1997. We are grateful to Beth Krizek for Ler 35S::AP1, 35S::AP3, and 35S::PI seeds; to Robert Sablowski for advice on the PCR genotyping method and for the 35S::AG transformation vector; to Marty Yanofsky for AGL5::GUS seeds; to Esther Koh for help with the Arabidopsis transformations; to Hajime Sakai for allowing us to mention his unpublished results; to Xuemei Chen, Jennifer Fletcher, Jian Hua, Mark Running, Hajime Sakai, and Eva Ziegelhoffer for valuable comments on the manuscript; and to the anonymous reviewers for their suggestions. This work was supported by National Science Foundation grant MCB-9204839 and National Institutes of Health grant GM-45697 to E.M.M.; J.L.R. was partially supported by a fellowship from Ministerio de Educación y Ciencia (Spain) and was formerly a European Molecular Biology Organization postdoctoral fellow.|
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|Deposited On:||12 Jun 2008|
|Last Modified:||26 Dec 2012 10:05|
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