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

JL Riechmann and EM Meyerowitz

Division of Biology, California Institute of Technology, Pasadena 91125, USA.

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.

Volume 8, Issue 7, pp. 1243-1259, 07/01/1997
Copyright © 1997 by The American Society for Cell Biology

This article has been cited by other articles:

				E. Piwarzyk, Y. Yang, and T. Jack Conserved C-Terminal Motifs of the Arabidopsis Proteins APETALA3 and PISTILLATA Are Dispensable for Floral Organ Identity Function Plant Physiology, December 1, 2007; 145(4): 1495 - 1505. [Abstract] [Full Text] [PDF]

				L. C. Hileman, J. F. Sundstrom, A. Litt, M. Chen, T. Shumba, and V. F. Irish Molecular and Phylogenetic Analyses of the MADS-Box Gene Family in Tomato Mol. Biol. Evol., November 1, 2006; 23(11): 2245 - 2258. [Abstract] [Full Text] [PDF]

				L. M. Zahn, H. Kong, J. H. Leebens-Mack, S. Kim, P. S. Soltis, L. L. Landherr, D. E. Soltis, C. W. dePamphilis, and H. Ma The Evolution of the SEPALLATA Subfamily of MADS-Box Genes: A Preangiosperm Origin With Multiple Duplications Throughout Angiosperm History Genetics, April 1, 2005; 169(4): 2209 - 2223. [Abstract] [Full Text] [PDF]

				R. J. Meister, H. Oldenhof, J. L. Bowman, and C. S. Gasser Multiple Protein Regions Contribute to Differential Activities of YABBY Proteins inReproductive Development Plant Physiology, February 1, 2005; 137(2): 651 - 662. [Abstract] [Full Text] [PDF]

				J. Nam, K. Kaufmann, Gün. Theißen, and M. Nei A simple method for predicting the functional differentiation of duplicate genes and its application to MIKC-type MADS-box genes Nucleic Acids Res., January 19, 2005; 33(2): e12 - e12. [Abstract] [Full Text] [PDF]

				M. Zik and V. F. Irish Global Identification of Target Genes Regulated by APETALA3 and PISTILLATA Floral Homeotic Gene Action PLANT CELL, January 1, 2003; 15(1): 207 - 222. [Abstract] [Full Text] [PDF]

				H. Lee, S.-S. Suh, E. Park, E. Cho, J. H. Ahn, S.-G. Kim, J. S. Lee, Y. M. Kwon, and I. Lee The AGAMOUS-LIKE 20 MADS domain protein integrates floral inductive pathways in Arabidopsis Genes & Dev., September 15, 2000; 14(18): 2366 - 2376. [Abstract] [Full Text]

				H. Sakai, B. A. Krizek, S. E. Jacobsen, and E. M. Meyerowitz Regulation of SUP Expression Identifies Multiple Regulators Involved in Arabidopsis Floral Meristem Development PLANT CELL, September 1, 2000; 12(9): 1607 - 1618. [Abstract] [Full Text]

				E. R. Alvarez-Buylla, S. Pelaz, S. J. Liljegren, S. E. Gold, C. Burgeff, G. S. Ditta, L. Ribas de Pouplana, L. Martinez-Castilla, and M. F. Yanofsky An ancestral MADS-box gene duplication occurred before the divergence of plants and animals PNAS, May 9, 2000; 97(10): 5328 - 5333. [Abstract] [Full Text] [PDF]

				J. L. Riechmann, T. Ito, and E. M. Meyerowitz Non-AUG Initiation of AGAMOUS mRNA Translation in Arabidopsis thaliana Mol. Cell. Biol., December 1, 1999; 19(12): 8505 - 8512. [Abstract] [Full Text] [PDF]

				Y. Yi and T. Jack An Intragenic Suppressor of the Arabidopsis Floral Organ Identity Mutant apetala3-1 Functions by Suppressing Defects in Splicing PLANT CELL, September 1, 1998; 10(9): 1465 - 1478. [Abstract] [Full Text]

				T. Hill, C. Day, S. Zondlo, A. Thackeray, and V. Irish Discrete spatial and temporal cis-acting elements regulate transcription of the Arabidopsis floral homeotic gene APETALA3 Development, January 5, 1998; 125(9): 1711 - 1721. [Abstract] [PDF]