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MetaCyc Chimeric Pathway: superpathway of gibberellin biosynthesis
Inferred from experiment

Pathway diagram: superpathway of gibberellin biosynthesis

If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.

Superclasses: BiosynthesisHormones BiosynthesisPlant Hormones BiosynthesisGibberellins and Gibberellin Precursors Biosynthesis
BiosynthesisSecondary Metabolites BiosynthesisTerpenoids BiosynthesisDiterpenoids BiosynthesisGibberellins and Gibberellin Precursors Biosynthesis

Some taxa known to possess parts of the pathway include : Arabidopsis thaliana col, Cucurbita maxima, Oryza sativa, Phaseolus coccineus, Pisum sativum, Spinacia oleracea, Triticum aestivum

Expected Taxonomic Range: Acetobacter, Azospirillum brasilense, Azospirillum lipoferum, Bacillus , Fusarium fujikuroi, Phaeosphaeria, Rhizobium phaseoli, Sphaceloma, Streptophytina

Note: This is a chimeric pathway, comprising reactions from multiple organisms, and typically will not occur in its entirety in a single organism. The taxa listed here are likely to catalyze only subsets of the reactions depicted in this pathway.

This super-pathway provides an overview of the complexity and interconnectivity of gibberellins biosynthesis. It is important to note that a given species shown here may not synthesize all the gibberellins presented. To know which gibberellins are found in a specfic species, refer to the subpathways given below.

General Background

At the time of this review, 136 fully characterized gibberellins (starting with GA1 [MacMillan68]) have been identified in more than a hundred vascular plant species, seven bacteria and seven fungi [Sponsel04, MacMillan01]. Of these gibberellins only a few have biological activity. Many of the GAs identified early in the history of the discovery of these hormones are the ones which possess the highest biological activity. These include GA1, GA3, GA4, GA5, GA6 and GA7. GA1 is the most active GA for stem elongation in Zea mays and Pisum sativum, while GA4 is the most active GA in Cucurbitaceae and in Arabidopsis thaliana. GA3 (gibberellic acid), on the other hand, has been identified in more than 40 plants and is the major GA in the fungus Fusarium fujikuroi. GA3 is used commercially to promote seed germination, stem elongation and fruit growth. In Lolium, GA5 and GA6 have been shown to enhance flowering, whilst GA1 and GA4 enhanced stem elongation [King03].

Gibberellins are diterpenes which, in higher plants, are synthesized in the plastids from glyceraldehyde-3-phosphate and pyruvate via the isopentenyl diphosphate (IPP). They all have either 19 or 20 carbon units grouped into either four or five ring systems (see gibberellin A12 and gibberellin A9, respectively). The fifth ring is a lactone ring. GAs containing a tetracyclic ent-gibberellane structure ( gibberellin A12) are called C20-GAs, whereas GAs containing a pentacyclic 20-nor-ent-gibberellane structure ( gibberellin A9) are called C19-GAs. C20-GAs do not usually have biological activity but can be metabolized to active C19-GAs (note that not all C19-GAs are bioactive).

Gibberellins are believed to be synthesized in young tissues of the shoot and also the developing seed. It is uncertain whether young root tissues also produce gibberellins. There is also some evidence that leaves may be the source of some biosynthesis.

Active gibberellins show many physiological effects, each depending on the type of gibberellin present as well as the species of plant. Some of the physiological processes stimulated by gibberellins are: i) stimulation of stem elongation by stimulating cell division and elongation, ii) stimulation of bolting/flowering in response to long days, iii) interruption of seed dormancy in plants requiring stratification or light to induce germination, iv) stimulation of enzyme production (α-amylases) in germinating cereal grains for mobilization of seed reserves, v) induction of maleness in dioecious flowers (sex expression), vi) parthenocarpic (seedless) fruit development, and vii) delay of senescence in leaves and citrus fruits.

Certain commercial chemicals which are used to stunt growth do so in part because they block the synthesis of gibberellins. Some of these chemicals are phosphon D, AMO-1618, cycocel, ancymidol and paclobutrazol (more inhibitors of GA biosynthesis can be found in [Sponsel04]). During active growth, the plant will maintain giberellin homeostasis by metabolizing most gibberellins by rapid hydroxylation to inactive conjugates. Active gibberellin A3 is degraded much slower which helps to explain the symptoms observed in the disease bakanae caused by the rice pathogen Fusarium fujikuroi. This pathogen produces large amounts of GA3 which it secretes. Inactive conjugates might be stored or translocated via the phloem and xylem before their release (activation) at the proper time and in the proper tissue.

Subpathways: gibberellin biosynthesis II (early C-3 hydroxylation), gibberellin biosynthesis III (early C-13 hydroxylation), gibberellin biosynthesis I (non C-3, non C-13 hydroxylation), gibberellin biosynthesis V, superpathway of gibberellin GA12 biosynthesis, GA12 biosynthesis, ent-kaurene biosynthesis I

Unification Links: AraCyc:PWY-5052, PlantCyc:PWY-5052

Revised 21-Oct-2013 by Caspi R, SRI International


King03: King RW, Evans LT, Mander LN, Moritz T, Pharis RP, Twitchin B (2003). "Synthesis of gibberellin GA6 and its role in flowering of Lolium temulentum." Phytochemistry 62(1);77-82. PMID: 12475622

MacMillan01: MacMillan J (2001). "Occurrence of Gibberellins in Vascular Plants, Fungi, and Bacteria." J Plant Growth Regul 20(4);387-442. PMID: 11986764

MacMillan68: MacMillan J, Takahashi N (1968). "Proposed procedure for the allocation of trivial names to the gibberellins." Nature 217(124);170-1. PMID: 5638147

Sponsel04: Sponsel V.M., Hedden P. (2004). "Gibberellin biosynthesis and inactivation." Plant Hormones. Biosynthesis, Signal transduction, Action! Kluwer Academic Publishers, Ed. P.J. Davies.

Other References Related to Enzymes, Genes, Subpathways, and Substrates of this Pathway

Anterola08: Anterola A, Shanle E (2008). "Genomic insights in moss gibberellin biosynthesis." The Bryologist 111(2);218-230.

Appleford05: Appleford NE, Evans DJ, Lenton JR, Gaskin P, Croker SJ, Devos KM, Phillips AL, Hedden P (2005). "Function and transcript analysis of gibberellin-biosynthetic enzymes in wheat." Planta NIL;1-15. PMID: 16160850

Cho04a: Cho EM, Okada A, Kenmoku H, Otomo K, Toyomasu T, Mitsuhashi W, Sassa T, Yajima A, Yabuta G, Mori K, Oikawa H, Toshima H, Shibuya N, Nojiri H, Omori T, Nishiyama M, Yamane H (2004). "Molecular cloning and characterization of a cDNA encoding ent-cassa-12,15-diene synthase, a putative diterpenoid phytoalexin biosynthetic enzyme, from suspension-cultured rice cells treated with a chitin elicitor." Plant J 37(1);1-8. PMID: 14675427

Davidson03: Davidson SE, Elliott RC, Helliwell CA, Poole AT, Reid JB (2003). "The pea gene NA encodes ent-kaurenoic acid oxidase." Plant Physiol 131(1);335-44. PMID: 12529541

Davidson04: Davidson SE, Smith JJ, Helliwell CA, Poole AT, Reid JB (2004). "The pea gene LH encodes ent-kaurene oxidase." Plant Physiol 134(3);1123-34. PMID: 14988475

Davis99: Davis G, Kobayashi M, Phinney BO, Lange T, Croker SJ, Gaskin P, MacMillan J (1999). "Gibberellin Biosynthesis in Maize. Metabolic Studies with GA(15), GA(24), GA(25), GA(7), and 2,3-Dehydro-GA(9)." Plant Physiol 121(3);1037-1045. PMID: 10557253

Fleet03: Fleet CM, Yamaguchi S, Hanada A, Kawaide H, David CJ, Kamiya Y, Sun TP (2003). "Overexpression of AtCPS and AtKS in Arabidopsis confers increased ent-kaurene production but no increase in bioactive gibberellins." Plant Physiol 132(2);830-9. PMID: 12805613

GarciaMartinez97: Garcia-Martinez JL, Lopez-Diaz I, Sanchez-Beltran MJ, Phillips AL, Ward DA, Gaskin P, Hedden P (1997). "Isolation and transcript analysis of gibberellin 20-oxidase genes in pea and bean in relation to fruit development." Plant Mol Biol 33(6);1073-84. PMID: 9154988

Harris05: Harris LJ, Saparno A, Johnston A, Prisic S, Xu M, Allard S, Kathiresan A, Ouellet T, Peters RJ (2005). "The maize An2 gene is induced by Fusarium attack and encodes an ent-copalyl diphosphate synthase." Plant Mol Biol 59(6);881-94. PMID: 16307364

Hayashi06: Hayashi K, Kawaide H, Notomi M, Sakigi Y, Matsuo A, Nozaki H (2006). "Identification and functional analysis of bifunctional ent-kaurene synthase from the moss Physcomitrella patens." FEBS Lett 580(26);6175-81. PMID: 17064690

Hedden12: Hedden P, Thomas SG (2012). "Gibberellin biosynthesis and its regulation." Biochem J 444(1);11-25. PMID: 22533671

Helliwell01: Helliwell CA, Chandler PM, Poole A, Dennis ES, Peacock WJ (2001). "The CYP88A cytochrome P450, ent-kaurenoic acid oxidase, catalyzes three steps of the gibberellin biosynthesis pathway." Proc Natl Acad Sci U S A 98(4);2065-70. PMID: 11172076

Helliwell01a: Helliwell CA, Sullivan JA, Mould RM, Gray JC, Peacock WJ, Dennis ES (2001). "A plastid envelope location of Arabidopsis ent-kaurene oxidase links the plastid and endoplasmic reticulum steps of the gibberellin biosynthesis pathway." Plant J 28(2);201-8. PMID: 11722763

Helliwell98: Helliwell CA, Sheldon CC, Olive MR, Walker AR, Zeevaart JA, Peacock WJ, Dennis ES (1998). "Cloning of the Arabidopsis ent-kaurene oxidase gene GA3." Proc Natl Acad Sci U S A 1998;95(15);9019-24. PMID: 9671797

Helliwell99: Helliwell CA, Poole A, Peacock WJ, Dennis ES (1999). "Arabidopsis ent-kaurene oxidase catalyzes three steps of gibberellin biosynthesis." Plant Physiol 1999;119(2);507-10. PMID: 9952446

Itoh01: Itoh H, Ueguchi-Tanaka M, Sentoku N, Kitano H, Matsuoka M, Kobayashi M (2001). "Cloning and functional analysis of two gibberellin 3 beta -hydroxylase genes that are differently expressed during the growth of rice." Proc Natl Acad Sci U S A 98(15);8909-14. PMID: 11438692

Johri08: Johri M M (2008). "Hormonal regulation in green plant lineage families." Physiology and Molecular Biology of Plants 14(1-2);23-38.

Kamienska76: Kamienska A (1976). "Isolation of gibberellins A3, A4 and A7 from Pinus attenuata pollen." Phytochemistry 15(3);421-424.

Karp04: Karp PD (2004). "Call for an enzyme genomics initiative." Genome Biol 5(8);401. PMID: 15287973

Kawaide00: Kawaide H, Sassa T, Kamiya Y (2000). "Functional analysis of the two interacting cyclase domains in ent-kaurene synthase from the fungus Phaeosphaeria sp. L487 and a comparison with cyclases from higher plants." J Biol Chem 275(4);2276-80. PMID: 10644675

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Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by Pathway Tools version 19.5 (software by SRI International) on Fri Apr 29, 2016, biocyc11.