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Gene Review

GA3  -  Ent-kaurene oxidase 1

Arabidopsis thaliana

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Disease relevance of GA3

  • This mutant showed dwarfism and late-flowering, but the phenotype was rescued by exogenous GA3 like known mutants defective in GA biosynthesis [1].
  • Arabidopsis plants overexpressing the KO cDNA under the control of the cauliflower mosaic virus 35S promoter, with or without a translational fusion to a modified green fluorescent protein (GFP), are very similar to wild-type (WT) plants under normal growth conditions [2].

High impact information on GA3

  • Because GA3 and spy-4 inhibited induction of the cytokinin primary-response gene, type-A Arabidopsis response regulator 5, SPY may interact with and modify elements from the phosphorelay cascade of the cytokinin signal transduction pathway [3].
  • The flf-1 mutant requires a greater than normal amount of an exogenous gibberellin (GA3) to decrease flowering time compared with the wild type or with vernalization-responsive late-flowering mutants, suggesting that the FLF gene product may block the promotion of flowering by GAs [4].
  • All of these phenotypes are also observed when wild-type Arabidopsis plants are repeatedly treated with gibberellin A3 (GA3) [5].
  • The deduced GA3 protein defines an additional class of cytochrome P450 enzymes [6].
  • Transgenic plants with increased levels of ADC2 transcript and elevated Put content showed dwarfism and late-flowering, and the phenotype was rescued by gibberellin A3 (GA3) application [7].

Biological context of GA3

  • In contrast to the Arabidopsis genome, multiple CPS-like, KS-like, and KO-like genes were identified in the rice genome, most of which are contiguously arranged [8].
  • Amounts of this transcript were less in the slender genotype than in the tall line and were reduced in GA-deficient genotypes by treatment with GA3, suggesting that there is feed-back regulation of GA 20-oxidase gene expression [9].
  • Short-term GA3 feeding of excised petioles induced lignin formation in the absence of a transcriptional activation of pathway-specific genes [10].
  • In the floral shoots of the ga1-2 mutant, transcript levels corresponding to each cDNA decreased dramatically after GA3 application, suggesting that GA biosynthesis may be controlled, at least in part, through down-regulation of the expression of the 20-oxidase genes [11].
  • The upl3 trichomes also often undergo an additional round of endoreplication resulting in enlarged nuclei with ploidy levels of up to 64C. upl3 plants are hypersensitive to gibberellic acid-3 (GA3), consistent with the role of gibberellins in trichome development [12].

Anatomical context of GA3

  • These data suggest that the AtKO1 protein links the plastid- and endoplasmic reticulum-located steps of the gibberellin biosynthesis pathway by association with the outer envelope of the plastid [13].
  • This protein kinase (ABR* kinase) was activated by pretreatment of guard cell protoplasts with ABA, but not by pretreatment with IAA, 2,4-D, kinetin or GA3 [14].
  • The subcellular location of KO and three of the UGTs involved in steviol glycoside biosynthesis was investigated by expression of GFP fusions and cell fractionation which revealed KO to be associated with the endoplasmic reticulum and the UGTs in the cytoplasm [15].

Associations of GA3 with chemical compounds

  • The expression of C2C-Prx was slightly induced by treatment with H2O2 (100 microM) or Fe3+/O2/DTT oxidation system, but not by ABA (50 microM) or GA3 (10 microM) [16].
  • Application of ABA induced the expression of both genes, but application of 2,4-D, BA, ABA and GA3 did not affect the expression of these genes [17].
  • Exogenous application of various chemicals such as ABA, GA3, kinetin, IAA, NaCl, and mannitol revealed that 10 mM IAA and 0.1 M NaCl significantly enhanced the accumulation of HSP81-2 and -3 transcripts [18].
  • The GUS expression was induced by 3-indolebutyric acid (IBA) and gibberellins (GA3 and GA4+7) [19].
  • Growth of an AtC/VIF1 T-DNA KO mutant was unaffected, but VI activity and hexose content were slightly increased [20].

Other interactions of GA3

  • The N-terminal portion of the cytochrome P450 protein ent-kaurene oxidase (AtKO1) directs GFP to chloroplasts in tobacco leaf transient assays [13].
  • The phyB mutant elongates more than the wild type in response to the same exogenous concentrations of GA3 or GA4, showing that the mutation causes an increase in responsiveness to GAs [21].
  • Metabolism of GA5 to GA3 and GA20 to GA1 was low [22].

Analytical, diagnostic and therapeutic context of GA3

  • Transcript abundance for the two most highly expressed genes was lower in apices of the GA-deficient ga1-2 mutant of Arabidopsis than in wild-type plants and increased after treatment of the mutant with GA3 [23].
  • By using a combination of conventional map-based cloning and random sequencing we identified a putative cytochrome P450 gene mapping to the same location as GA3 [6].


  1. dwarf and delayed-flowering 1, a novel Arabidopsis mutant deficient in gibberellin biosynthesis because of overexpression of a putative AP2 transcription factor. Magome, H., Yamaguchi, S., Hanada, A., Kamiya, Y., Oda, K. Plant J. (2004) [Pubmed]
  2. Plants with increased expression of ent-kaurene oxidase are resistant to chemical inhibitors of this gibberellin biosynthesis enzyme. Swain, S.M., Singh, D.P., Helliwell, C.A., Poole, A.T. Plant Cell Physiol. (2005) [Pubmed]
  3. Cross talk between gibberellin and cytokinin: the Arabidopsis GA response inhibitor SPINDLY plays a positive role in cytokinin signaling. Greenboim-Wainberg, Y., Maymon, I., Borochov, R., Alvarez, J., Olszewski, N., Ori, N., Eshed, Y., Weiss, D. Plant Cell (2005) [Pubmed]
  4. The FLF MADS box gene: a repressor of flowering in Arabidopsis regulated by vernalization and methylation. Sheldon, C.C., Burn, J.E., Perez, P.P., Metzger, J., Edwards, J.A., Peacock, W.J., Dennis, E.S. Plant Cell (1999) [Pubmed]
  5. Mutations at the SPINDLY locus of Arabidopsis alter gibberellin signal transduction. Jacobsen, S.E., Olszewski, N.E. Plant Cell (1993) [Pubmed]
  6. Cloning of the Arabidopsis ent-kaurene oxidase gene GA3. Helliwell, C.A., Sheldon, C.C., Olive, M.R., Walker, A.R., Zeevaart, J.A., Peacock, W.J., Dennis, E.S. Proc. Natl. Acad. Sci. U.S.A. (1998) [Pubmed]
  7. Overexpression of ADC2 in Arabidopsis induces dwarfism and late-flowering through GA deficiency. Alcázar, R., García-Martínez, J.L., Cuevas, J.C., Tiburcio, A.F., Altabella, T. Plant J. (2005) [Pubmed]
  8. An overview of gibberellin metabolism enzyme genes and their related mutants in rice. Sakamoto, T., Miura, K., Itoh, H., Tatsumi, T., Ueguchi-Tanaka, M., Ishiyama, K., Kobayashi, M., Agrawal, G.K., Takeda, S., Abe, K., Miyao, A., Hirochika, H., Kitano, H., Ashikari, M., Matsuoka, M. Plant Physiol. (2004) [Pubmed]
  9. Feed-back regulation of gibberellin biosynthesis and gene expression in Pisum sativum L. Martin, D.N., Proebsting, W.M., Parks, T.D., Dougherty, W.G., Lange, T., Lewis, M.J., Gaskin, P., Hedden, P. Planta (1996) [Pubmed]
  10. Impact of altered gibberellin metabolism on biomass accumulation, lignin biosynthesis, and photosynthesis in transgenic tobacco plants. Biemelt, S., Tschiersch, H., Sonnewald, U. Plant Physiol. (2004) [Pubmed]
  11. Isolation and expression of three gibberellin 20-oxidase cDNA clones from Arabidopsis. Phillips, A.L., Ward, D.A., Uknes, S., Appleford, N.E., Lange, T., Huttly, A.K., Gaskin, P., Graebe, J.E., Hedden, P. Plant Physiol. (1995) [Pubmed]
  12. The HECT ubiquitin-protein ligase (UPL) family in Arabidopsis: UPL3 has a specific role in trichome development. Downes, B.P., Stupar, R.M., Gingerich, D.J., Vierstra, R.D. Plant J. (2003) [Pubmed]
  13. A plastid envelope location of Arabidopsis ent-kaurene oxidase links the plastid and endoplasmic reticulum steps of the gibberellin biosynthesis pathway. Helliwell, C.A., Sullivan, J.A., Mould, R.M., Gray, J.C., Peacock, W.J., Dennis, E.S. Plant J. (2001) [Pubmed]
  14. Phosphorylation of the inward-rectifying potassium channel KAT1 by ABR kinase in Vicia guard cells. Mori, I.C., Uozumi, N., Muto, S. Plant Cell Physiol. (2000) [Pubmed]
  15. Spatial organisation of four enzymes from Stevia rebaudiana that are involved in steviol glycoside synthesis. Humphrey, T.V., Richman, A.S., Menassa, R., Brandle, J.E. Plant Mol. Biol. (2006) [Pubmed]
  16. Molecular cloning, expression, and functional characterization of a 2Cys-peroxiredoxin in Chinese cabbage. Cheong, N.E., Choi, Y.O., Lee, K.O., Kim, W.Y., Jung, B.G., Chi, Y.H., Jeong, J.S., Kim, K., Cho, M.J., Lee, S.Y. Plant Mol. Biol. (1999) [Pubmed]
  17. Characterization of two cDNAs (ERD10 and ERD14) corresponding to genes that respond rapidly to dehydration stress in Arabidopsis thaliana. Kiyosue, T., Yamaguchi-Shinozaki, K., Shinozaki, K. Plant Cell Physiol. (1994) [Pubmed]
  18. Analysis of tissue-specific expression of Arabidopsis thaliana HSP90-family gene HSP81. Yabe, N., Takahashi, T., Komeda, Y. Plant Cell Physiol. (1994) [Pubmed]
  19. Expression of NAC1 up-stream regulatory region and its relationship to the lateral root initiation induced by gibberellins and auxins. Wang, Y., Duan, L., Lu, M., Li, Z., Wang, M., Zhai, Z. Sci. China, C, Life Sci. (2006) [Pubmed]
  20. In Arabidopsis thaliana, the invertase inhibitors AtC/VIF1 and 2 exhibit distinct target enzyme specificities and expression profiles. Link, M., Rausch, T., Greiner, S. FEBS Lett. (2004) [Pubmed]
  21. Phytochrome B affects responsiveness to gibberellins in Arabidopsis. Reed, J.W., Foster, K.R., Morgan, P.W., Chory, J. Plant Physiol. (1996) [Pubmed]
  22. Gibberellin biosynthesis from gibberellin A12-aldehyde in endosperm and embryos of Marah macrocarpus. MacMillan, J., Ward, D.A., Phillips, A.L., Sánchez-Beltrán, M.J., Gaskin, P., Lange, T., Hedden, P. Plant Physiol. (1997) [Pubmed]
  23. Molecular cloning and functional expression of gibberellin 2- oxidases, multifunctional enzymes involved in gibberellin deactivation. Thomas, S.G., Phillips, A.L., Hedden, P. Proc. Natl. Acad. Sci. U.S.A. (1999) [Pubmed]
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