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Gene Review:

GA20OX1 - gibberellin 20 oxidase 1

Arabidopsis thaliana

Synonyms: ARABIDOPSIS THALIANA GIBBERELLIN 20-OXIDASE 1, AT2301, ATGA20OX1, GA REQUIRING 5, GA5, ...

Xu, Y.L. et al., Wu, K. et al., Biemelt, S. et al., Xu, Y.L. et al., Martin, D.N. et al., et al.

Biemelt, Tschiersch, Sonnewald,

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Disease relevance of GA5

A cDNA clone corresponding to the putative GA 20-oxidase genomic sequence was constructed with the reverse transcription-PCR method, and the identity of the cDNA clone was confirmed by analyzing the capability of the fusion protein expressed in Escherichia coli to convert GA53 to GA44 and GA19 to GA20 [1].
To investigate the impact of altered GA levels on plant growth and metabolism, transgenic tobacco (Nicotiana tabacum) plants have been engineered to express either a GA20-oxidase (AtGA20-ox) or a GA2-oxidase (AtGA2-ox) gene from Arabidopsis under control of the cauliflower mosaic virus 35S promoter [2].

High impact information on GA5

However, due to feedback regulation, expression of GA5 and GA4, the gene coding for the subsequent 3beta-hydroxylase, was greatly increased to compensate for the effects of the P16 transgene [3].
This up-regulation of GA 2-oxidase gene expression by GA contrasts GA-induced down-regulation of genes encoding the biosynthetic enzymes GA 20-oxidase and GA 3beta-hydroxylase [4].
The GA5 locus of Arabidopsis thaliana encodes a multifunctional gibberellin 20-oxidase: molecular cloning and functional expression [1].
The ga5 semidwarf mutant contains a G-->A point mutation that inserts a translational stop codon in the protein-coding sequence, thus confirming that the GA5 locus encodes GA 20-oxidase [1].
Here, we report isolation of a genomic clone for GA 20-oxidase from a genomic library of the long-day species Arabidopsis thaliana Heynh., strain Columbia, by using the pumpkin cDNA clone as a heterologous probe [1].

Biological context of GA5

This genomic clone contains a GA 20-oxidase gene that consists of three exons and two introns [1].
Previously, a cDNA clone encoding a GA 20-oxidase [gibberellin, 2-oxoglutarate:oxygen oxidoreductase (20-hydroxylating, oxidizing), EC 1.14.11.-] was isolated by immunoscreening a cDNA library from liquid endosperm of pumpkin (Cucurbita maxima L.) with antibodies against partially purified GA 20-oxidase [1].
These results demonstrate that GA levels and, hence, plant growth and development can be modified by manipulation of GA 20-oxidase expression in transgenic plants [5].
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 [6].
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 [7].

Associations of GA5 with chemical compounds

The ga5 mutant had reduced levels of the C19-GAs, which indicates that the product of the GA5 gene catalyzes the elimination of C-20 at the aldehyde level [8].
Expression studies with cycloheximide indicated that the antagonistic effects of GA and BR on GA5 require de novo protein synthesis [9].
Our results show that auxin differentially up-regulates the expression of various genes involved in GA metabolism, in particular several AtGA20ox and AtGA2ox genes [10].

Other interactions of GA5

One of these was used to isolate two different full-length cDNA clones, At2301 and At2353, from shoots of the GA-deficient Arabidopsis mutant ga1-2 [11].
These results suggest that Put accumulation affects GA metabolism through the repression of biosynthetic steps catalyzed by GA 20-oxidase and GA 3-oxidase [12].
Metabolism of GA5 to GA3 and GA20 to GA1 was low [13].
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 [14].
Therefore, neither phytochrome A nor hytochrome B appears to regulate GA biosynthesis from GA12 to GA4 during seed germination, since the conversion of GA12 to GA9 is regulated by one enzyme (GA 20-oxidase) [15].

Analytical, diagnostic and therapeutic context of GA5

Northern blot analysis indicated that the level of GA 20-oxidase mRNA was higher in plants in LD than in SD conditions, with highest level of expression in the shoot tips and elongating stems [16].
Degenerate oligonucleotide primers were used to obtain a polymerase chain reaction product from spinach genomic DNA that has a high homology with GA 20-oxidase cDNAs from Cucurbita maxima L. and Arabidopsis thaliana Heynh [16].

References

The GA5 locus of Arabidopsis thaliana encodes a multifunctional gibberellin 20-oxidase: molecular cloning and functional expression. Xu, Y.L., Li, L., Wu, K., Peeters, A.J., Gage, D.A., Zeevaart, J.A. Proc. Natl. Acad. Sci. U.S.A. (1995) [Pubmed]
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]
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]
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]
Modification of gibberellin production and plant development in Arabidopsis by sense and antisense expression of gibberellin 20-oxidase genes. Coles, J.P., Phillips, A.L., Croker, S.J., García-Lepe, R., Lewis, M.J., Hedden, P. Plant J. (1999) [Pubmed]
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]
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]
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]
Control of specific gene expression by gibberellin and brassinosteroid. Bouquin, T., Meier, C., Foster, R., Nielsen, M.E., Mundy, J. Plant Physiol. (2001) [Pubmed]
Transcriptional regulation of gibberellin metabolism genes by auxin signaling in Arabidopsis. Frigerio, M., Alabad??, D., P??rez-G??mez, J., Garc??a-C??rcel, L., Phillips, A.L., Hedden, P., Bl??zquez, M.A. Plant Physiol. (2006) [Pubmed]
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]
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]
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]
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]
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]
Molecular cloning and photoperiod-regulated expression of gibberellin 20-oxidase from the long-day plant spinach. Wu, K., Li, L., Gage, D.A., Zeevaart, J.A. Plant Physiol. (1996) [Pubmed]

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GA20OX3	Arabidopsis thaliana
GA20OX4	Arabidopsis thaliana
GA20OX2	Arabidopsis thaliana
Os03g0856700	Oryza sativa Japonica Group

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