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Gene Review

AG  -  MADS domain transcription factor AGAMOUS

Arabidopsis thaliana

Synonyms: AGAMOUS, AGAMOUS PROTEIN, F13C5.130, F13C5_130
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Disease relevance of AG

  • Furthermore, gain-of-function analysis demonstrated that ectopic AG function results in precocious flowering and the formation of terminal flowers at apices of both the primary inflorescence and axillary branches of transgenic Arabidopsis plants in which AG expression is under the control of the 35S promoter from cauliflower mosaic virus [1].
  • To examine the DNA-binding activity of the AGAMOUS protein, double-stranded oligonucleotides with random sequences of 40 bp in the central region were synthesized and mixed with the AGAMOUS MADS domain overproduced in Escherichia coli [2].

High impact information on AG

  • We also show that AG represses WUS at later stages of floral development, thus creating a negative feedback loop that is required for the determinate growth of floral meristems [3].
  • The homeotic gene AGAMOUS (AG) has dual roles in specifying organ fate and limiting stem cell proliferation in Arabidopsis flowers [3].
  • On the basis of these observations, it has been proposed that AG and AP2 act in an antagonistic fashion [4].
  • We found that AG RNA is present in the stamen and carpel primordia but is undetectable in sepal and petal primordia throughout early wild-type flower development, consistent with the mutant phenotype [5].
  • Analysis of a LEAFY-responsive enhancer in the homeotic gene AGAMOUS indicates that direct interaction of LEAFY with this enhancer is required for its activity in plants [6].

Biological context of AG

  • Based on these results, a model is proposed that suggests that the products of these homeotic genes are each active in fields occupying two adjacent whorls, AP2 in the two outer whorls, PI and AP3 in whorls two and three, and AG in the two inner whorls [7].
  • The molecular dissection of AP1, AP3, PI and AG indicates that the boundaries of the dimerization domains of these proteins vary [8].
  • Further, the phenotypes of multiple mutant lines indicate that the wild-type products of the AGAMOUS and APETALA2 genes interact antagonistically [7].
  • To test and extend present models for establishment of floral organ identity, we constructed a transgenic line that expresses the AGAMOUS gene under the control of the APETALA3 promotor (pAP3::AG) [9].
  • Similar phenotypes were also observed in lfy ap1 double mutants carrying a 35S-AG transgene [1].

Associations of AG with chemical compounds

  • We show here that the AG MADS domain and the I region are necessary and sufficient for DNA binding in vitro and that AG binds to DNA as a dimer [10].
  • Floral transcription factor AGAMOUS interacts in vitro with a leucine-rich repeat and an acid phosphatase protein complex [11].
  • Intron/exon structure is conserved in relation to AG and the Antirrhinum AG orthologue, PLENA (PLE), and low-stringency Southern analysis demonstrated the absence of additional genes in the poplar genome with significant PTAG1/2 homology [12].
  • Comparison of the methylated sequences in SUPERMAN and AGAMOUS suggests that hypermethylation could involve DNA secondary structures formed by pyrimidine-rich sequences [13].
  • During the course of characterizing fragments bound to an Arabidopsis floral protein AGAMOUS in vivo, a gene encoding a putative serine/threonine protein kinase was found on one of the fragments [14].

Regulatory relationships of AG


Other interactions of AG

  • However, these proteins exhibit "partner-specificity" for the formation of DNA-binding dimers; only AP1 homodimers, AG homodimers, and AP3/PI heterodimers are capable of binding to CArG-box sequences [20].
  • HUA1 and HUA2 were identified previously as regulators of stamen and carpel identities and floral determinacy because the recessive hua1-1 or hua2-1 allele affected these processes in plants with a lower dosage of functional AG (either homozygous for the weak ag-4 allele or heterozygous for the strong ag-1 allele) [21].
  • AP2 seems to keep the AG gene inactive in the two outer whorls while the converse is likely in the two inner whorls [7].
  • Furthermore, a direct in vivo association of SEU proteins with the AG cis-regulatory element was shown by chromatin immunoprecipitation [22].
  • When pAP3::AG is crossed to the homeotic mutants apetala1, apetala3, pistilla, agamous and superman, novel floral phenotypes result [9].

Analytical, diagnostic and therapeutic context of AG

  • This binding was further confirmed by immunoprecipitation experiments using in vitro synthesized AG and AGL K domains [23].
  • This supposed cadastral function of SAP is supported by in situ hybridization experiments showing ectopic expression of AG in the sap mutant [24].
  • Cloning and sequence analysis of agamous suggest that it encodes a protein with a high degree of sequence similarity to the DNA-binding region of transcription factors from yeast and humans and to the product of a homeotic gene from Antirrhinum [25].
  • HEN1 may achieve these functions by regulating the expression of AG. hen1 single mutants exhibit pleiotropic phenotypes such as reduced organ size, altered rosette leaf shape and increased number of coflorescences, during most stages of development [26].
  • PCR cloning using degenerate primers targeted to the MADS-box domain revealed the presence of over 27 MADS-box genes within black spruce (Picea mariana), including several with extensive homology to either AP1 or AGAMOUS, both known to regulate flower development in Arabidopsis [27].


  1. Determination of Arabidopsis floral meristem identity by AGAMOUS. Mizukami, Y., Ma, H. Plant Cell (1997) [Pubmed]
  2. Nucleotide sequences recognized by the AGAMOUS MADS domain of Arabidopsis thaliana in vitro. Shiraishi, H., Okada, K., Shimura, Y. Plant J. (1993) [Pubmed]
  3. A molecular link between stem cell regulation and floral patterning in Arabidopsis. Lohmann, J.U., Hong, R.L., Hobe, M., Busch, M.A., Parcy, F., Simon, R., Weigel, D. Cell (2001) [Pubmed]
  4. Ectopic expression of the floral homeotic gene AGAMOUS in transgenic Arabidopsis plants alters floral organ identity. Mizukami, Y., Ma, H. Cell (1992) [Pubmed]
  5. Negative regulation of the Arabidopsis homeotic gene AGAMOUS by the APETALA2 product. Drews, G.N., Bowman, J.L., Meyerowitz, E.M. Cell (1991) [Pubmed]
  6. Activation of a floral homeotic gene in Arabidopsis. Busch, M.A., Bomblies, K., Weigel, D. Science (1999) [Pubmed]
  7. Genetic interactions among floral homeotic genes of Arabidopsis. Bowman, J.L., Smyth, D.R., Meyerowitz, E.M. Development (1991) [Pubmed]
  8. DNA-binding properties of Arabidopsis MADS domain homeotic proteins APETALA1, APETALA3, PISTILLATA and AGAMOUS. Riechmann, J.L., Wang, M., Meyerowitz, E.M. Nucleic Acids Res. (1996) [Pubmed]
  9. Targeted misexpression of AGAMOUS in whorl 2 of Arabidopsis flowers. Jack, T., Sieburth, L., Meyerowitz, E. Plant J. (1997) [Pubmed]
  10. Functional domains of the floral regulator AGAMOUS: characterization of the DNA binding domain and analysis of dominant negative mutations. Mizukami, Y., Huang, H., Tudor, M., Hu, Y., Ma, H. Plant Cell (1996) [Pubmed]
  11. Floral transcription factor AGAMOUS interacts in vitro with a leucine-rich repeat and an acid phosphatase protein complex. Gamboa, A., Paéz-Valencia, J., Acevedo, G.F., Vázquez-Moreno, L., Alvarez-Buylla, R.E. Biochem. Biophys. Res. Commun. (2001) [Pubmed]
  12. Structure and expression of duplicate AGAMOUS orthologues in poplar. Brunner, A.M., Rottmann, W.H., Sheppard, L.A., Krutovskii, K., DiFazio, S.P., Leonardi, S., Strauss, S.H. Plant Mol. Biol. (2000) [Pubmed]
  13. Ectopic hypermethylation of flower-specific genes in Arabidopsis. Jacobsen, S.E., Sakai, H., Finnegan, E.J., Cao, X., Meyerowitz, E.M. Curr. Biol. (2000) [Pubmed]
  14. A serine/threonine protein kinase gene isolated by an in vivo binding procedure using the Arabidopsis floral homeotic gene product, AGAMOUS. Ito, T., Takahashi, N., Shimura, Y., Okada, K. Plant Cell Physiol. (1997) [Pubmed]
  15. LEUNIG regulates AGAMOUS expression in Arabidopsis flowers. Liu, Z., Meyerowitz, E.M. Development (1995) [Pubmed]
  16. Mutual Regulation of Arabidopsis thaliana Ethylene-responsive Element Binding Protein and a Plant Floral Homeotic Gene, APETALA2. Ogawa, T., Uchimiya, H., Kawai-Yamada, M. Ann. Bot. (2007) [Pubmed]
  17. A new role of the Arabidopsis SEPALLATA3 gene revealed by its constitutive expression. Castillejo, C., Romera-Branchat, M., Pelaz, S. Plant J. (2005) [Pubmed]
  18. The homeotic protein AGAMOUS controls microsporogenesis by regulation of SPOROCYTELESS. Ito, T., Wellmer, F., Yu, H., Das, P., Ito, N., Alves-Ferreira, M., Riechmann, J.L., Meyerowitz, E.M. Nature (2004) [Pubmed]
  19. AGL24, SHORT VEGETATIVE PHASE, and APETALA1 redundantly control AGAMOUS during early stages of flower development in Arabidopsis. Gregis, V., Sessa, A., Colombo, L., Kater, M.M. Plant Cell (2006) [Pubmed]
  20. Dimerization specificity of Arabidopsis MADS domain homeotic proteins APETALA1, APETALA3, PISTILLATA, and AGAMOUS. Riechmann, J.L., Krizek, B.A., Meyerowitz, E.M. Proc. Natl. Acad. Sci. U.S.A. (1996) [Pubmed]
  21. HUA1, a regulator of stamen and carpel identities in Arabidopsis, codes for a nuclear RNA binding protein. Li, J., Jia, D., Chen, X. Plant Cell (2001) [Pubmed]
  22. APETALA1 and SEPALLATA3 interact with SEUSS to mediate transcription repression during flower development. Sridhar, V.V., Surendrarao, A., Liu, Z. Development (2006) [Pubmed]
  23. Specific interactions between the K domains of AG and AGLs, members of the MADS domain family of DNA binding proteins. Fan, H.Y., Hu, Y., Tudor, M., Ma, H. Plant J. (1997) [Pubmed]
  24. Arabidopsis STERILE APETALA, a multifunctional gene regulating inflorescence, flower, and ovule development. Byzova, M.V., Franken, J., Aarts, M.G., de Almeida-Engler, J., Engler, G., Mariani, C., Van Lookeren Campagne, M.M., Angenent, G.C. Genes Dev. (1999) [Pubmed]
  25. The protein encoded by the Arabidopsis homeotic gene agamous resembles transcription factors. Yanofsky, M.F., Ma, H., Bowman, J.L., Drews, G.N., Feldmann, K.A., Meyerowitz, E.M. Nature (1990) [Pubmed]
  26. HEN1 functions pleiotropically in Arabidopsis development and acts in C function in the flower. Chen, X., Liu, J., Cheng, Y., Jia, D. Development (2002) [Pubmed]
  27. Characterization of an AGAMOUS homologue from the conifer black spruce (Picea mariana) that produces floral homeotic conversions when expressed in Arabidopsis. Rutledge, R., Regan, S., Nicolas, O., Fobert, P., Côté, C., Bosnich, W., Kauffeldt, C., Sunohara, G., Séguin, A., Stewart, D. Plant J. (1998) [Pubmed]
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