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Pathway Description
Gibberellin Biosynthesis III (Non C-3, Non C-13 Hydroxylation)
Arabidopsis thaliana
Category:
Metabolite Pathway
Sub-Category:
Metabolic
Created: 2017-03-02
Last Updated: 2023-10-25
Gibberellins (GAs) are a large class of tetracyclic diterpenoid plant hormones that regulate numerous growth and developmental processes, such as seed germination, organ elongation, and flowering induction. All known gibberellins share an ent-gibberellane skeleton and follow the same synthesis pathway. Biosynthesis begins in the plasmids via the terpenoid pathway and finishes in the endoplasmic reticulum and cytosol where they undergo modification until a biologically-active form is reached (GA1, GA3, GA4, or GA7). Gibberellins are named in the order that they are discovered (GA1 through GAn). Gibberellin biosynthesis via non C-3, non C-13 hydroxylation occurs in the cytosol and converts the inactive GA12 to the active GA4, and inactive GA36 and GA13. The first two reactions are catalyzed by gibberellin 20-oxidase, requiring Fe2+ and L-ascorbate as cofactors. It first converts gibberellin A12 into gibberellin A15 and then into gibberellin A24. Gibberellin A24 has three different fates. The first route involves the conversion of gibberellin A24 into gibberellin A9 by gibberellin 20-oxidase and then the subsequent conversion of gibberellin A9 into the active gibberellin A4 by gibberellin 3-oxidase. It requires Fe2+ and L-ascorbate as cofactors. The second route involves the conversion of gibberellin A24 into gibberellin A36 by gibberellin 3-oxidase. The third route involves the conversion of gibberellin A24 into gibberellin A25 by gibberellin 20-oxidase and then the subsequent conversion of gibberellin A25 into gibberellin A13 by a not yet elucidated gibberellin oxidase (coloured orange in the image).
References
Gibberellin Biosynthesis III (Non C-3, Non C-13 Hydroxylation) References
Yamaguchi S: Gibberellin metabolism and its regulation. Annu Rev Plant Biol. 2008;59:225-51. doi: 10.1146/annurev.arplant.59.032607.092804.
Pubmed: 18173378
Phillips AL, Ward DA, Uknes S, Appleford NE, Lange T, Huttly AK, Gaskin P, Graebe JE, Hedden P: Isolation and expression of three gibberellin 20-oxidase cDNA clones from Arabidopsis. Plant Physiol. 1995 Jul;108(3):1049-57. doi: 10.1104/pp.108.3.1049.
Pubmed: 7630935
Xu YL, Li L, Wu K, Peeters AJ, Gage DA, Zeevaart JA: The GA5 locus of Arabidopsis thaliana encodes a multifunctional gibberellin 20-oxidase: molecular cloning and functional expression. Proc Natl Acad Sci U S A. 1995 Jul 3;92(14):6640-4. doi: 10.1073/pnas.92.14.6640.
Pubmed: 7604047
Hisamatsu T, King RW, Helliwell CA, Koshioka M: The involvement of gibberellin 20-oxidase genes in phytochrome-regulated petiole elongation of Arabidopsis. Plant Physiol. 2005 Jun;138(2):1106-16. doi: 10.1104/pp.104.059055. Epub 2005 May 27.
Pubmed: 15923331
Mitchum MG, Yamaguchi S, Hanada A, Kuwahara A, Yoshioka Y, Kato T, Tabata S, Kamiya Y, Sun TP: Distinct and overlapping roles of two gibberellin 3-oxidases in Arabidopsis development. Plant J. 2006 Mar;45(5):804-18. doi: 10.1111/j.1365-313X.2005.02642.x.
Pubmed: 16460513
Matsushita A, Furumoto T, Ishida S, Takahashi Y: AGF1, an AT-hook protein, is necessary for the negative feedback of AtGA3ox1 encoding GA 3-oxidase. Plant Physiol. 2007 Mar;143(3):1152-62. doi: 10.1104/pp.106.093542. Epub 2007 Feb 2.
Pubmed: 17277098
Chiang HH, Hwang I, Goodman HM: Isolation of the Arabidopsis GA4 locus. Plant Cell. 1995 Feb;7(2):195-201. doi: 10.1105/tpc.7.2.195.
Pubmed: 7756830
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