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Gene Review

AP1  -  Floral homeotic protein APETALA 1

Arabidopsis thaliana

Synonyms: AGAMOUS-like 7, AGL7, APETALA1, F4N2.9, F4N2_9, ...
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High impact information on AP1


Biological context of AP1

  • The molecular dissection of AP1, AP3, PI and AG indicates that the boundaries of the dimerization domains of these proteins vary [6].
  • Activation of the Arabidopsis B class homeotic genes by APETALA1 [7].
  • We provide genetic evidence for the role of AP1 in these interactions by showing that the floral phenotype in the ap1 agl24 svp triple mutant is significantly enhanced [8].
  • Using chromatin immunoprecipitation, we show that the floral homeotic PISTILLATA (PI) protein, required for petal and stamen development, has the ability to bind directly to the promoter region of AP1 [9].
  • In this study, the unique and redundant functions of these two genes has been mapped to the four protein domains that characterize type-II MADS-domain proteins by expressing all 15 chimeric combinations of AP1 and CAL cDNA regions under control of the AP1 promoter in ap1-1 loss-of-function plants [10].

Anatomical context of AP1


Associations of AP1 with chemical compounds

  • However, ap1mS, a farnesyl cysteine-acceptor mutant of AP1, as well as the GFP-ap1mS fusion protein failed to direct the development of compound terminal flowers but instead induced novel phenotypes when ectopically expressed in Arabidopsis [12].

Physical interactions of AP1

  • Taken together, these studies suggest that SEP3 interacts with AP1 to promote normal flower development [13].

Regulatory relationships of AP1

  • Furthermore, the early flowering phenotype of plants constitutively expressing AP1 is significantly enhanced by constitutive SEP3 expression [13].
  • We demonstrate that BPEp is positively regulated downstream of APETALA3, PISTILLATA, APETALA1 and PISTILLATA3 and is negatively regulated downstream of AGAMOUS [14].
  • Kinetic studies, using transgenic Arabidopsis plants in which both AP3 and PI are under post-translational control, show that AP1 transcript levels are downregulated within 2 h of AP3/PI activation [9].
  • We show here that this negative regulation can be mutual because TFL1 expression is downregulated in plants constitutively expressing AP1 [15].
  • The Arabidopsis AGL8 MADS box gene is expressed in inflorescence meristems and is negatively regulated by APETALA1 [16].

Other interactions of AP1

  • 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 [17].
  • Both the AP3/PI heterodimer and the AP1 or AG homodimers are formed when the three corresponding proteins are present together [17].
  • Dimerization specificity of Arabidopsis MADS domain homeotic proteins APETALA1, APETALA3, PISTILLATA, and AGAMOUS [17].
  • The AP1-SEU protein-protein interaction was supported by synergistic genetic interactions between ap1 and seu mutations [18].
  • An AP1/AGL9 group of MADS box gene, OMADS1, with extensive homology to the Arabidopsis AGAMOUS-like 6 gene (AGL6) was characterized from orchid (Oncidium Gower Ramsey) [19].

Analytical, diagnostic and therapeutic context of AP1

  • To identify proteins that may interact with AP1 and CAL, we used the yeast two-hybrid assay [13].
  • RNA tissue in situ hybridization studies show that AP1 RNA accumulates uniformly throughout young floral primordia, but is absent from the inflorescence meristem [2].
  • 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 [20].


  1. Repression of AGAMOUS-LIKE 24 is a crucial step in promoting flower development. Yu, H., Ito, T., Wellmer, F., Meyerowitz, E.M. Nat. Genet. (2004) [Pubmed]
  2. Regulation of the arabidopsis floral homeotic gene APETALA1. Gustafson-Brown, C., Savidge, B., Yanofsky, M.F. Cell (1994) [Pubmed]
  3. Transcriptional activation of APETALA1 by LEAFY. Wagner, D., Sablowski, R.W., Meyerowitz, E.M. Science (1999) [Pubmed]
  4. Genetic control of shoot and flower meristem behavior. Liljegren, S.J., Yanofsky, M.F. Curr. Opin. Cell Biol. (1996) [Pubmed]
  5. 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]
  6. 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]
  7. Activation of the Arabidopsis B class homeotic genes by APETALA1. Ng, M., Yanofsky, M.F. Plant Cell (2001) [Pubmed]
  8. 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]
  9. Direct regulation of the floral homeotic APETALA1 gene by APETALA3 and PISTILLATA in Arabidopsis. Sundström, J.F., Nakayama, N., Glimelius, K., Irish, V.F. Plant J. (2006) [Pubmed]
  10. Unique and redundant functional domains of APETALA1 and CAULIFLOWER, two recently duplicated Arabidopsis thaliana floral MADS-box genes. Alvarez-Buylla, E.R., García-Ponce, B., Garay-Arroyo, A. J. Exp. Bot. (2006) [Pubmed]
  11. Positional cloning of the wheat vernalization gene VRN1. Yan, L., Loukoianov, A., Tranquilli, G., Helguera, M., Fahima, T., Dubcovsky, J. Proc. Natl. Acad. Sci. U.S.A. (2003) [Pubmed]
  12. Prenylation of the floral transcription factor APETALA1 modulates its function. Yalovsky, S., Rodríguez-Concepción, M., Bracha, K., Toledo-Ortiz, G., Gruissem, W. Plant Cell (2000) [Pubmed]
  13. APETALA1 and SEPALLATA3 interact to promote flower development. Pelaz, S., Gustafson-Brown, C., Kohalmi, S.E., Crosby, W.L., Yanofsky, M.F. Plant J. (2001) [Pubmed]
  14. BIGPETALp, a bHLH transcription factor is involved in the control of Arabidopsis petal size. Szécsi, J., Joly, C., Bordji, K., Varaud, E., Cock, J.M., Dumas, C., Bendahmane, M. EMBO J. (2006) [Pubmed]
  15. Interactions among APETALA1, LEAFY, and TERMINAL FLOWER1 specify meristem fate. Liljegren, S.J., Gustafson-Brown, C., Pinyopich, A., Ditta, G.S., Yanofsky, M.F. Plant Cell (1999) [Pubmed]
  16. The Arabidopsis AGL8 MADS box gene is expressed in inflorescence meristems and is negatively regulated by APETALA1. Mandel, M.A., Yanofsky, M.F. Plant Cell (1995) [Pubmed]
  17. 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]
  18. APETALA1 and SEPALLATA3 interact with SEUSS to mediate transcription repression during flower development. Sridhar, V.V., Surendrarao, A., Liu, Z. Development (2006) [Pubmed]
  19. Ectopic expression of an orchid (Oncidium Gower Ramsey) AGL6-like gene promotes flowering by activating flowering time genes in Arabidopsis thaliana. Hsu, H.F., Huang, C.H., Chou, L.T., Yang, C.H. Plant Cell Physiol. (2003) [Pubmed]
  20. 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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