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Gene Review

GA1  -  Ent-copalyl diphosphate synthase

Arabidopsis thaliana

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Disease relevance of GA1


High impact information on GA1

  • In transgenic Arabidopsis plants overexpressing P16, there was a severe reduction in the amounts of C20-GA intermediates, accumulation of large amounts of inactive GA25 and GA17, a reduction in GA4 content, and a small increase in GA1 [3].
  • A decreased feedback of GA possibly causes an induction of GA biosynthesis based upon the expression of genes encoding copalyl diphosphate synthase (CPS; GA1) and GA 2-oxidase (AtGA2ox1) [4].
  • These genes encode the enzymes ent-copalyl diphosphate synthase (CPS) and ent-kaurene synthase, which catalyze the first two committed steps in GA biosynthesis [5].
  • These pathways are represented by the genes CO, FCA, and GA1, which act in the long-day, autonomous, and gibberellin pathways, respectively [6].
  • When plants were transferred from SD to LD conditions there was a slight decrease in the level of GA53 and an increase in the levels of C19-GAs, GA9, GA20, GA1, and GA8, indicating that GA 20-oxidase activity is stimulated in LD conditions [7].

Biological context of GA1


Associations of GA1 with chemical compounds

  • This result indicates that the GA1 gene encodes the enzyme ent-kaurene synthetase A, which catalyzes the conversion of GGPP to CPP [1].
  • Overall, GA1 and GA4 levels decreased and abscisic acid levels increased compared with wild-type plants [10].
  • The Arabidopsis GA1 gene encodes copalyl diphosphate synthase, which catalyzes the first committed step in the gibberellin biosynthetic pathway [8].
  • 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].

Other interactions of GA1

  • 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) [13].


  1. The Arabidopsis GA1 locus encodes the cyclase ent-kaurene synthetase A of gibberellin biosynthesis. Sun, T.P., Kamiya, Y. Plant Cell (1994) [Pubmed]
  2. 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]
  3. Feedback regulation of GA5 expression and metabolic engineering of gibberellin levels in Arabidopsis. Xu, Y.L., Li, L., Gage, D.A., Zeevaart, J.A. Plant Cell (1999) [Pubmed]
  4. Ethylene-mediated enhancement of apical hook formation in etiolated Arabidopsis thaliana seedlings is gibberellin dependent. Vriezen, W.H., Achard, P., Harberd, N.P., Van Der Straeten, D. Plant J. (2004) [Pubmed]
  5. Overexpression of AtCPS and AtKS in Arabidopsis confers increased ent-kaurene production but no increase in bioactive gibberellins. Fleet, C.M., Yamaguchi, S., Hanada, A., Kawaide, H., David, C.J., Kamiya, Y., Sun, T.P. Plant Physiol. (2003) [Pubmed]
  6. Analysis of flowering time control in Arabidopsis by comparison of double and triple mutants. Reeves, P.H., Coupland, G. Plant Physiol. (2001) [Pubmed]
  7. Gibberellins and stem growth in Arabidopsis thaliana. Effects of photoperiod on expression of the GA4 and GA5 loci. Xu, Y.L., Gage, D.A., Zeevaart, J.A. Plant Physiol. (1997) [Pubmed]
  8. Characterization of cis-regulatory regions responsible for developmental regulation of the gibberellin biosynthetic gene GA1 in Arabidopsis thaliana. Chang, C.W., Sun, T.P. Plant Mol. Biol. (2002) [Pubmed]
  9. Developmental regulation of the gibberellin biosynthetic gene GA1 in Arabidopsis thaliana. Silverstone, A.L., Chang, C., Krol, E., Sun, T.P. Plant J. (1997) [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. 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]
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