Biosynthesis of the gibberellin plant hormones

MacMillan, Jake

doi:10.1039/np9971400221

Cited by 134 publications

(81 citation statements)

References 173 publications

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“…In our experiments, the wild-type strain converted GA 12 to nonpolar products, consistent with the results of Bearder et al (28), who found that GA 12 is metabolized mainly to the non-3␤-hydroxylated GA, GA 9 . The small amount of GA 3 formed from GA 12 may be the result of the low rate of 3␤-hydroxylation.…”

Section: Discussionmentioning

confidence: 99%

“…1) are identical for plants and fungi, but the pathways diverge thereafter. The major end product of the pathway in G. fujikuroi is gibberellic acid (GA 3 ), which is a minor GA component in most plant species.…”

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confidence: 99%

“…GAs were first identified as secondary products of the fungus Gibberella fujikuroi (mating population C) and are also produced by other fungal species (2)(3)(4). The early steps of the GA-biosynthetic pathway from transgeranylgeranyl diphosphate to GA 12 -aldehyde ( Fig.…”

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confidence: 99%

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The P450–1 gene of Gibberella fujikuroi encodes a multifunctional enzyme in gibberellin biosynthesis

Rojas

Hedden

Gaskin

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

126

106

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Recent studies have shown that the genes of the gibberellin (GA) biosynthesis pathway in the fungus Gibberella fujikuroi are organized in a cluster of at least seven genes. P450 -1 is one of four cytochrome P450 monooxygenase genes in this cluster. Disruption of the P450 -1 gene in the GA-producing wild-type strain IMI 58289 led to total loss of GA production. Analysis of the P450 -1-disrupted mutants indicated that GA biosynthesis was blocked immediately after ent-kaurenoic acid. The function of the P450 -1 gene product was investigated further by inserting the gene into mutants of G. fujikuroi that lack the entire GA gene cluster; the gene was highly expressed under GA production conditions in the absence of the other GA-biosynthesis genes. Cultures of transformants containing P450 -1 converted ent- cytochrome P450 ͉ ent-kaurenoid metabolism ͉ GA14 synthase

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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The P450–1 gene of Gibberella fujikuroi encodes a multifunctional enzyme in gibberellin biosynthesis

Rojas

Hedden

Gaskin

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

126

106

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“…In line with current nomenclature for GA biosynthesis enzymes and the corresponding genes (10), we will refer to GA3 as AtKO1. The genes encoding the enzymes catalyzing the conversion of KA to ent-7␣-hydroxykaurenoic acid (7OH-KA) and 7OH-KA to GA 12 -aldehyde have not been isolated, but it is known that these reactions are likely to be catalyzed by cytochrome P450s requiring O 2 and NADPH for activity (11).…”

mentioning

confidence: 99%

The CYP88A cytochrome P450, ent -kaurenoic acid oxidase, catalyzes three steps of the gibberellin biosynthesis pathway

Helliwell

Poole

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

282

144

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We have shown that ent-kaurenoic acid oxidase, a member of the CYP88A subfamily of cytochrome P450 enzymes, catalyzes the three steps of the gibberellin biosynthetic pathway from entkaurenoic acid to GA 12. A gibberellin-responsive barley mutant, grd5, accumulates ent-kaurenoic acid in developing grains. Three independent grd5 mutants contain mutations in a gene encoding a member of the CYP88A subfamily of cytochrome P450 enzymes, defined by the maize Dwarf3 protein. Mutation of the Dwarf3 gene gives rise to a gibberellin-responsive dwarf phenotype, but the lesion in the gibberellin biosynthesis pathway has not been identified. Arabidopsis thaliana has two CYP88A genes, both of which are expressed. Yeast strains expressing cDNAs encoding each of the two Arabidopsis and the barley CYP88A enzymes catalyze the three steps of the GA biosynthesis pathway from ent-kaurenoic acid to GA 12. Sequence comparison suggests that the maize Dwarf3 locus also encodes ent-kaurenoic acid oxidase. G ibberellins (GAs) are an important class of plant hormone involved in the regulation of processes from seed germination through the development and reproduction of plants (1). GA biosynthesis is catalyzed by three classes of enzymes: terpene cyclases catalyze the synthesis of ent-kaurene from geranylgeranyl diphosphate; cytochrome P450 monooxygenases catalyze the steps of the pathway from ent-kaurene to GA 12 ; and soluble dioxygenases catalyze the final steps of the pathway.Genes encoding enzymes for the two terpene cyclasecatalyzed steps, copalyl diphosphate synthase and kaurene synthase, have been isolated from a number of species (2, 3). Similarly, a wide range of 2-oxoglutarate-dependent dioxygenases encoding GA 7-oxidase, GA 20-oxidase, GA 2␤, 3␤-hydroxylase, GA 3␤-hydroxylase, and GA 2-oxidase activities have been isolated (2,(4)(5)(6). GA3 from Arabidopsis thaliana is the only gene encoding a cytochrome P450-mediated step of GA biosynthesis isolated (7), although the maize Dwarf3 gene is likely also to be involved in GA biosynthesis, and it encodes a member of the CYP88A subfamily of cytochrome P450 enzymes (8). GA3 encodes the cytochrome P450 CYP701A3 (7) and has been shown to catalyze the three-step oxidation of ent-kaurene to ent-kaurenoic acid (KA) (9). In line with current nomenclature for GA biosynthesis enzymes and the corresponding genes (10), we will refer to GA3 as AtKO1. The genes encoding the enzymes catalyzing the conversion of KA to ent-7␣-hydroxykaurenoic acid (7OH-KA) and 7OH-KA to GA 12 -aldehyde have not been isolated, but it is known that these reactions are likely to be catalyzed by cytochrome P450s requiring O 2 and NADPH for activity (11).The maize Dwarf3 gene encodes the cytochrome P450 CYP88A1 (8). The dwarf3 mutant is a GA-responsive dwarf (12); however, the reaction catalyzed by CYP88A1 has not been defined (2). It is likely that Dwarf3 is a GA biosynthetic enzyme, and therefore it may catalyze one of the steps between KA and GA 12 . We have described the isolation of a cDNA-encoding CYP88A2 from pumpk...

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“…Gibberellin transport might be governed by processes other than simple pH-dependent diffusion across the membrane (Nour & Rubery, 1984). Rapid metabolism and inactivation of GA taken up by the cell might also have occurred (Hedden & Kamiya, 1997 ;MacMillan, 1997). In addition, physiological effects of altered extracellular pH might have been superimposed on the response to changed GA permeability (Bush & Jones, 1988).…”

Section:       mentioning

confidence: 99%

Gibberellins: regulating genes and germination

Ritchie

Gilroy

1998

New Phytologist

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The range of processes regulated by gibberellins (GAs) covers all aspects of the life history of the plant from seed germination to vegetative growth and flowering. In seeds there has been an intensive search, using the techniques of both biochemistry and cell biology, for the regulatory molecules linking GA perception to gene regulation and the events of germination. Although a GA receptor has yet to be identified, the site of perception has been localized to the plasma membrane. Calmodulin, Ca2+ and cGMP have also been identified as elements of the GA signal transduction pathway. These regulators parallel many of the signalling elements identified in the transduction of other signals such as phytochrome and ABA. Studies of GA‐regulated gene expression, principally of the α‐amylases of cereal aleurone, have identified core GA‐responsive promoter elements, such as the gibberellin response element (GARE), box‐1 and pyrimidine boxes, as well as elements that may lend specificity to GA‐regulated expression, such as the Opaque‐2‐similar element (O2S), and TRE and CRE motifs. One of the most striking features of all of these studies of the molecular basis of GA action is the interaction of GA‐dependent regulatory elements with those of other factors such as ABA. GA‐response elements also appear to be conserved between disparate GA‐response systems. For example, Myb transcription factors appear to regulate a multitude of GA‐induced genes in cereal aleurone as well as to alter GA responses when expressed in Arabidopsis. Thus the study of GA signal transduction and response systems is highlighting the conservation of regulatory elements used by plants. These common factors, used by distinct signal transduction systems, provide a molecular basis for the integration of the GA signal with other growth regulators that is the hallmark of plant growth and development.

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Biosynthesis of the gibberellin plant hormones

Cited by 134 publications

References 173 publications

The P450–1 gene of Gibberella fujikuroi encodes a multifunctional enzyme in gibberellin biosynthesis

The P450–1 gene of Gibberella fujikuroi encodes a multifunctional enzyme in gibberellin biosynthesis

The CYP88A cytochrome P450, ent -kaurenoic acid oxidase, catalyzes three steps of the gibberellin biosynthesis pathway

Gibberellins: regulating genes and germination

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