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Gene Review

GA3OX1  -  gibberellin 3-beta-dioxygenase 1

Arabidopsis thaliana

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Disease relevance of GA4

  • (Heynh. ) was expressed in Escherichia coli, from which cell lysates converted [14C]gibberellin (GA)9 and [14C]GA20 to radiolabeled GA4 and GA1, respectively, thereby confirming that GA4 encodes a GA 3beta-hydroxylase [1].

High impact information on GA4

  • Conversely, a loss-of-function rgl1 line had reduced GA4 expression and exhibited GA-independent activation of seed germination, leaf expansion, flowering, stem elongation, and floral development, as detected by resistance to the GA biosynthesis inhibitor paclobutrazol [2].
  • The effect of rga on GA4 gene expression and the effect of GA on RGA protein level allow us to identify part of the mechanism by which GA homeostasis is achieved [3].
  • Using RNA gel blot analyses, we studied the regulation of two Arabidopsis genes, GA4 and GA4H (for GA4 homolog), both of which encode GA 3beta-hydroxylases that catalyze the final biosynthetic step to produce bioactive GAs [4].
  • Because the rga mutation abolished the high level of expression of the GA biosynthetic gene GA4 in the ga1-3 mutant background, we conclude that RGA may also play a role in controlling GA biosynthesis [5].
  • A cDNA containing a complete open reading frame of the pea GA4-related gene was amplified by polymerase chain reaction from each isoline [6].

Biological context of GA4

  • Gibberellin 3-oxidase in Arabidopsis is encoded by a multigene family consisting of at least four members, designated AtGA3ox1 to AtGA3ox4 [7].
  • We describe the isolation of the Le gene of pea, which controls internode elongation and originally was described by Mendel. Heterologous screening of a pea cDNA library yielded a partial clone that was 61% identical to coding regions of the putative Arabidopsis gibberellin 3 beta-hydroxylase gene, GA4 [6].
  • Function and substrate specificity of the gibberellin 3beta-hydroxylase encoded by the Arabidopsis GA4 gene [1].
  • To broaden our understanding of gibberellin (GA) biosynthesis and the mechanism whereby GA homeostasis is maintained in plants, we have investigated the degree to which the enzyme GA 3-oxidase (GA3ox) limits the formation of bioactive GAs in elongating shoots of hybrid aspen (Populus tremula x Populus tremuloides) [8].
  • Expression of GA20-oxidase and GA3-oxidase genes was greatly reduced in the knockout seeds, suggesting the potential involvement of the zinc finger protein in GA biosynthesis [9].

Associations of GA4 with chemical compounds

  • Overall, GA1 and GA4 levels decreased and abscisic acid levels increased compared with wild-type plants [10].
  • Together, the data suggest that the developmental defects in the ms33 mutant are unrelated to ABA levels, but may be causally associated with reduced levels of IAA, GA1 and GA4, compared to WT flowers [11].
  • The relative activity of GAs for promoting germination of uniconazole-treated seeds was GA4 > GA1 = GA9 > GA20 [12].
  • Quantitative Reverse Transcription (QRT)-PCR data showed that GA down-regulated genes AtGA3ox1, AtGA20ox1 and SCARECROW-LIKE3 (SCL3) were up-regulated and the GA up-regulated genes AtGA2ox1 and AtExp1 were down-regulated in estradiol-treated leaves of inducible PcGA2ox1 overexpressors; neighbouring non-treated leaves showing no significant changes [13].

Other interactions of GA4

  • We showed that expression of two genes, AtGA3ox1 and AtGA3ox2, encoding GA 3-oxidase, which catalyzes the terminal biosynthetic step, was mainly localized in the cortex and endodermis of embryo axes in germinating seeds [14].
  • These results suggest that Put accumulation affects GA metabolism through the repression of biosynthetic steps catalyzed by GA 20-oxidase and GA 3-oxidase [15].
  • Eight of them are members of the early-13-hydroxylation pathway (GA53, GA44, GA19, GA17, GA20, GA1, GA29, and GA8), six are members of the early-3-hydroxylation pathway (GA37, GA27, GA36, GA13, GA4, and GA34), and the remaining six are members of the non-3,13-hydroxylation pathway (GA12, GA15, GA24, GA25, GA9, and GA51) [16].
  • 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 [17].
  • Overexpression of pumpkin GA 7-oxidase (CmGA7ox) in Arabidopsis (Arabidopsis thaliana) resulted in seedlings with elongated roots, taller plants that flower earlier with only a little increase in bioactive GA4 levels compared to control plants [18].


  1. Function and substrate specificity of the gibberellin 3beta-hydroxylase encoded by the Arabidopsis GA4 gene. Williams, J., Phillips, A.L., Gaskin, P., Hedden, P. Plant Physiol. (1998) [Pubmed]
  2. Arabidopsis RGL1 encodes a negative regulator of gibberellin responses. Wen, C.K., Chang, C. Plant Cell (2002) [Pubmed]
  3. Repressing a repressor: gibberellin-induced rapid reduction of the RGA protein in Arabidopsis. Silverstone, A.L., Jung, H.S., Dill, A., Kawaide, H., Kamiya, Y., Sun, T.P. Plant Cell (2001) [Pubmed]
  4. Phytochrome regulation and differential expression of gibberellin 3beta-hydroxylase genes in germinating Arabidopsis seeds. Yamaguchi, S., Smith, M.W., Brown, R.G., Kamiya, Y., Sun, T. Plant Cell (1998) [Pubmed]
  5. The Arabidopsis RGA gene encodes a transcriptional regulator repressing the gibberellin signal transduction pathway. Silverstone, A.L., Ciampaglio, C.N., Sun, T. Plant Cell (1998) [Pubmed]
  6. Mendel's stem length gene (Le) encodes a gibberellin 3 beta-hydroxylase. Lester, D.R., Ross, J.J., Davies, P.J., Reid, J.B. Plant Cell (1997) [Pubmed]
  7. Distinct and overlapping roles of two gibberellin 3-oxidases in Arabidopsis development. Mitchum, M.G., Yamaguchi, S., Hanada, A., Kuwahara, A., Yoshioka, Y., Kato, T., Tabata, S., Kamiya, Y., Sun, T.P. Plant J. (2006) [Pubmed]
  8. Cloning and overproduction of gibberellin 3-oxidase in hybrid aspen trees. Effects on gibberellin homeostasis and development. Israelsson, M., Mellerowicz, E., Chono, M., Gullberg, J., Moritz, T. Plant Physiol. (2004) [Pubmed]
  9. The BME3 (Blue Micropylar End 3) GATA zinc finger transcription factor is a positive regulator of Arabidopsis seed germination. Liu, P.P., Koizuka, N., Martin, R.C., Nonogaki, H. Plant J. (2005) [Pubmed]
  10. Alteration of hormone levels in transgenic tobacco plants overexpressing the rice homeobox gene OSH1. Kusaba, S., Kano-Murakami, Y., Matsuoka, M., Tamaoki, M., Sakamoto, T., Yamaguchi, I., Fukumoto, M. Plant Physiol. (1998) [Pubmed]
  11. Pleiotropic effects of the male sterile33 (ms33) mutation in Arabidopsis are associated with modifications in endogenous gibberellins, indole-3-acetic acid and abscisic acid. Fei, H., Zhang, R., Pharis, R.P., Sawhney, V.K. Planta (2004) [Pubmed]
  12. Effects of gibberellins on seed germination of phytochrome-deficient mutants of Arabidopsis thaliana. Yang, Y.Y., Nagatani, A., Zhao, Y.J., Kang, B.J., Kendrick, R.E., Kamiya, Y. Plant Cell Physiol. (1995) [Pubmed]
  13. Modification of plant architecture through the expression of GA 2-oxidase under the control of an estrogen inducible promoter in Arabidopsis thaliana L. Curtis, I.S., Hanada, A., Yamaguchi, S., Kamiya, Y. Planta (2005) [Pubmed]
  14. Distinct cell-specific expression patterns of early and late gibberellin biosynthetic genes during Arabidopsis seed germination. Yamaguchi, S., Kamiya, Y., Sun, T. Plant J. (2001) [Pubmed]
  15. 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]
  16. Endogenous gibberellins in Arabidopsis thaliana and possible steps blocked in the biosynthetic pathways of the semidwarf ga4 and ga5 mutants. Talon, M., Koornneef, M., Zeevaart, J.A. Proc. Natl. Acad. Sci. U.S.A. (1990) [Pubmed]
  17. Phytochrome B affects responsiveness to gibberellins in Arabidopsis. Reed, J.W., Foster, K.R., Morgan, P.W., Chory, J. Plant Physiol. (1996) [Pubmed]
  18. Ectopic expression of pumpkin gibberellin oxidases alters gibberellin biosynthesis and development of transgenic Arabidopsis plants. Radi, A., Lange, T., Niki, T., Koshioka, M., Lange, M.J. Plant Physiol. (2006) [Pubmed]
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