Identification of gibberellin A4 in Pisum sativum L. and the effects of applied gibberellins A9, A4, A5 and A3 on the le mutant

Poole, Andrew T.; Ross, John J.; Lawrence, Naomi L.; Reid, James B.

doi:10.1007/bf00024783

Cited by 9 publications

(8 citation statements)

References 30 publications

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“…For each mutant, the position of the block was determined by bioassay and metabolic studies. However, it is unlikely that the three genes, Le, GA4, and Dy, have the same function as the Dl gene of maize, since normal seedlings of pea (13), arabidopsis (14), and rice (14) do not metabolize GA20 to GA5, and GA5 is metabolized to GA3 in normal and le seedlings of pea (26). In addition, no evidence has been published for the presence of endogenous GA5 and GA3 in seedlings of pea, arabidopsis, and rice.…”

Section: Discussionmentioning

confidence: 99%

The dwarf-1 (dt) Mutant of Zea mays blocks three steps in the gibberellin-biosynthetic pathway.

Spray

Kobayashi²,

Suzuki³

et al. 1996

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

111

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In plants, gibberellin (GA)-responding mutants have been used as tools to identify the genes that control specific steps in the GA-biosynthetic pathway. They have also been used to determine which native GAs are active per se, i.e., further metabolism is not necessary for bioactivity. We present metabolic evidence that the Dl gene of maize (Zea mays L.) controls the three biosynthetic steps: GA20 to GA1, GA20 to GA5, and GA5 to GA3. We also present evidence that three gibberellins, GA1, GA5, and GA3, have per se activity in stimulating shoot elongation in maize. The metabolic evidence comes from the injection of [17-13C,3H]GA20 and [17-13C,3H] GA5 into seedlings of dl and controls (normal and d5), followed by isolation and identification of the 13C-labeled metabolites by full-scan GC-MS and Kovats retention index.For the controls, GA20 was metabolized to GA1, GA3, and GA5; GA5 was metabolized to GA3. For the dl mutant, GA20 was not metabolized to GA1, GA3, or to GA5, and GA5 was not metabolized to GA3. The bioassay evidence is based on dosage response curves using dl seedlings for assay. GA1, GA3, and GA5 had similar bioactivities, and they were 10-times more active than GA20.linear and there is no evidence for a metabolic grid with the other pathways, as has been shown for cell-free preparations obtained from seeds of bean, cucumber, and pea (for review, see ref.3).The biological significance of the metabolic studies in maize comes from the use of GA mutants that exhibit a dwarf phenotype, yet respond by normal growth to applied GAs. Thus, the relative responses of the mutants to specific GAs together with information on the role of the genes in controlling specific steps in the pathway have led to the conclusion that only a limited number of GAs in the pathway are active per se, i.e., they do not require further metabolism to be bioactive (for reviews, see refs. 10-12).The purpose of the present study was to examine the metabolic steps, GA20 to GA5, GA5 to GA3 and GA20 to GA1 in relation to the dl mutation (blockage after GA20). To this end, [17-13C,3H]GA2o and [17-13C,3H]GAs were fed to dl seedlings and to controls (normal and d5 seedlings) and the metabolites from the feeds were analyzed by full-scan GC-MS. In addition, the bioactivities of GA20, GA1, GA5, and GA3 were determined using dl seedlings for assay.The gibberellins (GAs) are tetracarbocyclic diterpenes that occur naturally in higher plants (1). There is continued interest in the biosynthetic origin of the GAs since some of them are known to act as native regulators controlling a range of growth responses, including seed germination, floral development, and shoot elongation (for reviews, see refs. 2 and 3).All GAs are biosynthesized from trans-geranylgeranyl diphosphate (GGDP) via ent-copalyl diphosphate (CDP) and the tetracyclic hydrocarbon, ent-kaurene. ent-Kaurene is sequentially oxidized to ent-7a-hydroxykaurenoic acid, which is then rearranged to GA12-aldehyde and oxidized to GA12. At least three pathways diverge from GA12-aldehyde and ...

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Section: Discussionmentioning

confidence: 99%

The dwarf-1 (dt) Mutant of Zea mays blocks three steps in the gibberellin-biosynthetic pathway.

Spray

Kobayashi²,

Suzuki³

et al. 1996

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

111

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“…The branch pathway from GA 20 to GA 3 occurs also in barley embryos (41) and may be common, although not ubiquitous, in higher plants. The conversion of GA 5 to GA 3 has also been demonstrated in pea shoots (93) and in a cell-free system from rice anthers (58), although because GA 5 is not formed in these systems (50,57), the function of this activity is unclear.…”

Section: β-Hydroxylases and Related Enzymesmentioning

confidence: 99%

GIBBERELLIN BIOSYNTHESIS: Enzymes, Genes and Their Regulation

Hedden

Kamiya

1997

Annu. Rev. Plant. Physiol. Plant. Mol. Biol.

545

396

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The recent impressive progress in research on gibberellin (GA) biosynthesis has resulted primarily from cloning of genes encoding biosynthetic enzymes and studies with GA-deficient and GA-insensitive mutants. Highlights include the cloning of ent-copalyl diphosphate synthase and ent-kaurene synthase (formally ent-kaurene synthases A and B) and the demonstration that the former is targeted to the plastid; the finding that the Dwarf-3 gene of maize encodes a cytochrome P450, although of unknown function; and the cloning of GA 20-oxidase and 3beta-hydroxylase genes. The availability of cDNA and genomic clones for these enzymes is enabling the mechanisms by which GA concentrations are regulated by environmental and endogenous factors to be studied at the molecular level. For example, it has been shown that transcript levels for GA 20-oxidase and 3beta-hydroxylase are subject to feedback regulation by GA action and, in the case of the GA 20-oxidase, are regulated by light. Also discussed is other new information, particularly from mutants, that has added to our understanding of the biosynthetic pathway, the enzymes, and their regulation and tissue localization.

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“…In contrast, there was only a non-significant trend toward increased stem elongation and increased numbers of new nodes in response to GA 5 application. This implies that Hancornia seedlings may have a very reduced level of GA 3 -oxidase activity, which otherwise might convert GA 5 into the growth-active GA 3 (Durley et al 1973;Fujioka et al 1990;Moritz and Monteiro 1994;Poole et al 1995;Wolbang et al 2004) and/or that GA 5 has very low per se growth-activity. Finally, the fact that Hancornia responds strongly to exogenous application of the per se growth-active GAs, GA 1 , and GA 3 , indicates that a defect in the GA signal transduction pathway is not likely to be responsible for the inherently slow shoot elongation rate of the young Hancornia control seedlings.…”

Section: Discussionmentioning

confidence: 96%

Growth-active gibberellins overcome the very slow shoot growth of Hancornia speciosa, an important fruit tree from the Brazilian “Cerrado”

Caldas

Machado²,

Caldas

et al. 2009

Trees

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Shoot elongation of Hancornia speciosa, an endangered tree from the Brazilian savannah ''Cerrado'', is very slow, thus limiting nursery production of plants. Gibberellins (GAs) A 1 , A 3 , and A 5 , and two inhibitors of GA biosynthesis, trinexapac-ethyl and ancymidol were applied to shoots of Hancornia seedlings. GA 1 and GA 3 significantly stimulated shoot elongation, while GA 5 had no significant effect. Trinexapac-ethyl and ancymidol, both at 100 lg per seedling, inhibited shoot elongation up to 45 days after treatment, though the effect was statistically significant only for ancymidol. Somewhat surprisingly, exogenous GA 3 more effectively stimulated shoot elongation in SD-grown plants, than in LD-grown plants. The results from exogenous application of GAs and inhibitors of GA biosynthesis imply that Hancornia shoot growth is controlled by GAs, and that level of endogenous growthactive GAs is likely to be the limiting factor for shoot elongation in Hancornia. Application of GAs thus offer a practical method for nursery production of Hancornia seedlings for outplanting into the field.

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Identification of gibberellin A4 in Pisum sativum L. and the effects of applied gibberellins A9, A4, A5 and A3 on the le mutant

Cited by 9 publications

References 30 publications

The dwarf-1 (dt) Mutant of Zea mays blocks three steps in the gibberellin-biosynthetic pathway.

The dwarf-1 (dt) Mutant of Zea mays blocks three steps in the gibberellin-biosynthetic pathway.

GIBBERELLIN BIOSYNTHESIS: Enzymes, Genes and Their Regulation

Growth-active gibberellins overcome the very slow shoot growth of Hancornia speciosa, an important fruit tree from the Brazilian “Cerrado”

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