Overexpression of a Novel Class of Gibberellin 2-Oxidases Decreases Gibberellin Levels and Creates Dwarf Plants

Schomburg, Fritz M.; Bizzell, Colleen M.; Lee, Dong Ju; Zeevaart, Jan A. D.; Amasino, Richard M.

doi:10.1105/tpc.005975

Cited by 366 publications

(345 citation statements)

References 32 publications

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“…Phillips, and P. Hedden, unpublished data;Wang et al, 2004), and similar results have been obtained in other transgenic plants with related GA 2-oxidases from poplar (Populus spp), rice, and runner bean (Phaseolus coccineus) (Sakamoto et al, 2001;Busov et al, 2003;Appleford et al, 2007). An activation tagging screen for dwarf mutants (Schomburg et al, 2003) identified two further, structurally distinct Arabidopsis genes that encoded 2-oxoglutaratedependent dioxygenase enzymes with GA 2-oxidase activity. These enzymes, GA2ox7 and GA2ox8, were shown to be active against C 20 -GAs, such as GA 12 and GA 53 , but are not capable of using C 19 -GAs as substrates.…”

Section: Introductionsupporting

confidence: 66%

“…Loss of function of the Arabidopsis GA2ox2 gene increases GA 4 levels in dark-imbibed seeds and thereby promotes germination in the mutant (Yamauchi et al, 2007). Double mutants in GA2ox7 and GA2ox8 show an increased seed germination rate in the presence of the GA biosynthesis inhibitor ancymidol and have elongated hypocotyls (Schomburg et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

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Genetic Analysis Reveals That C19-GA 2-Oxidation Is a Major Gibberellin Inactivation Pathway inArabidopsis

et al. 2008

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Bioactive hormone concentrations are regulated both at the level of hormone synthesis and through controlled inactivation. Based on the ubiquitous presence of 2β-hydroxylated gibberellins (GAs), a major inactivating pathway for the plant hormone GA seems to be via GA 2-oxidation. In this study, we used various approaches to determine the role of C19-GA 2-oxidation in regulating GA concentration and GA-responsive plant growth and development. We show that Arabidopsis thaliana has five C19-GA 2-oxidases, transcripts for one or more of which are present in all organs and at all stages of development examined. Expression of four of the five genes is subject to feed-forward regulation. By knocking out all five Arabidopsis C19-GA 2-oxidases, we show that C19-GA 2-oxidation limits bioactive GA content and regulates plant development at various stages during the plant life cycle: C19-GA 2-oxidases prevent seed germination in the absence of light and cold stimuli, delay the vegetative and floral phase transitions, limit the number of flowers produced per inflorescence, and suppress elongation of the pistil prior to fertilization. Under GA-limited conditions, further roles are revealed, such as limiting elongation of the main stem and side shoots. We conclude that C19-GA 2-oxidation is a major GA inactivation pathway regulating development in Arabidopsis.

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Section: Introductionsupporting

confidence: 66%

Section: Introductionmentioning

confidence: 99%

Genetic Analysis Reveals That C19-GA 2-Oxidation Is a Major Gibberellin Inactivation Pathway inArabidopsis

et al. 2008

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“…The resulting PCR products were used as templates for the second round of PCR using BrRGAr100 (5#-TTTACCAAACACCGCAG-GGG-3#) and AD-2, or BrRGAf1610 (5#-TTGGCTTTGTTTAATGGAGGCG-3#) and AD-1, for 5#or 3#, respectively. The PCR reactions were performed as previously reported (Schomberg et al, 2003) and the PCR products were gel purified, cloned, and sequenced. The resulting sequences were used to design primers, 5#2 to 2 (5#-AGGCCTAGTTCACTTCAAAGGTTA-3#) and 3#31 to 34 (5#-TCACCGGTTCGGTCCGGGTTT-3#), to amplify BrRGA1, and 5#F32 (5#-TGGAAAAGCATCTTCAGTTCTCCA-3#) and 3#R2632 (5#-TCACCGGT-TCGGTCCGGGTTT-3#) to amplify BrRGA2 using genomic DNA from both dwf2 and wild-type plants as templates.…”

Section: Comparative Fine Mapping and Cloning Of Brrga1 And Brrga2mentioning

confidence: 99%

“…Total RNA was isolated from shoots of 2-week-old plants treated with water, or 5 mL of 1 mM GA 3 , for various times. RNA isolation and RT-PCR were performed as described (Schomberg et al, 2003). Degenerate primers GA3ox 492 (5#-TCACCATCAYYGGMTCRCCTC-3#) and GA3ox 840 (5#-AGATCATCGCGAAWWACYTGTA-3#), designed from conserved sequences of Arabidopsis and pea GA3ox, were used to amplify B. rapa GA3ox.…”

Section: Rna Analysismentioning

confidence: 99%

A Novel Dwarfing Mutation in a Green Revolution Gene from Brassica rapa

et al. 2005

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Mutations in the biosynthesis or signaling pathways of gibberellin (GA) can cause dwarfing phenotypes in plants, and the use of such mutations in plant breeding was a major factor in the success of the Green Revolution. DELLA proteins are GA signaling repressors whose functions are conserved in different plant species. Recent studies show that GA promotes stem growth by causing degradation of DELLA proteins via the ubiquitin-proteasome pathway. The most widely utilized dwarfing alleles in wheat (Triticum aestivum; e.g. Rht-B1b and Rht-D1b) encode GA-resistant forms of a DELLA protein that function as dominant and constitutively active repressors of stem growth. All of the previously identified dominant DELLA repressors from several plant species contain N-terminal mutations. Here we report on a novel dwarf mutant from Brassica rapa (Brrga1-d) that is caused by substitution of a conserved amino acid in the C-terminal domain of a DELLA protein. Brrga1-d, like N-terminal DELLA mutants, retains its repressor function and accumulates to high levels, even in the presence of GA. However, unlike wild-type and N-terminal DELLA mutants, Brrga1-d does not interact with a protein component required for degradation, suggesting that the mutated amino acid causes dwarfism by preventing an interaction needed for its degradation. This novel mutation confers nondeleterious dwarf phenotypes when transferred to Arabidopsis (Arabidopsis thaliana) and oilseed rape (Brassica napus), indicating its potential usefulness in other crop species.Dwarfism is a desirable characteristic for many agricultural plants. In grain crops, dwarfism can reduce lodging and increase harvest index, and the breeding of dwarf wheat (Triticum aestivum) and rice (Oryza sativa) cultivars was a major factor in the success of the Green Revolution (Khush, 2001). Dwarfism is often caused by mutations in genes controlling the biosynthesis or signaling pathway of the plant hormone GA (Peng et al., 1999;Hedden, 2003;Sun and Gubler, 2004). The most widely utilized semi-dwarf wheat cultivars in agriculture contain the Rht-B1b or Rht-D1b allele that encodes a mutant form of a DELLA protein, a GA signaling repressor (Peng et al., 1999;Hedden, 2003).DELLA proteins encoded by Rht and its orthologs in Arabidopsis (Arabidopsis thaliana; GAI, RGA, RGL1, and RGL2), maize (Zea mays; d8), grape (Vitis vinifera; VvGAI), barley (Hordeum vulgare; SLN1), and rice (SLR1) have conserved function as repressors of GA signaling (Sun and Gubler, 2004). Five DELLA protein genes (GAI, RGA, RGL1, RGL2, and RGL3) are present in Arabidopsis, and with the exception of RGL3, these genes have been shown to share partially overlapping roles in repressing GA-regulated plant growth and development . Genetic analysis indicates that RGA and GAI are the major repressors that modulate GA-mediated vegetative growth and floral induction; RGL2 is important in regulating seed germination; and RGL1 and RGL2, along with RGA, control flower development King et al., 2001;Lee et al., 2002;Cheng et al., 2004;Tyle...

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“…Bioactive GA 1 , GA 4 , their immediate precursors GA 20 and GA 9 , and C20 GAs are deactivated by GA2-oxidases [4,[15][16][17][18]. However, 2-oxidation is not the only mechanism by which bioactive GAs are deactivated.…”

Section: Introductionmentioning

confidence: 99%

Gibberellin homeostasis and plant height control by EUI and a role for gibberellin in root gravity responses in rice

et al. 2008

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The rice Eui (ELONGATED UPPERMOST INTERNODE) gene encodes a cytochrome P450 monooxygenase that deactivates bioactive gibberellins (GAs). In this study, we investigated controlled expression of the Eui gene and its role in plant development. We found that Eui was differentially induced by exogenous GAs and that the Eui promoter had the highest activity in the vascular bundles. The eui mutant was defective in starch granule development in root caps and Eui overexpression enhanced starch granule generation and gravity responses, revealing a role for GA in root starch granule development and gravity responses. Experiments using embryoless half-seeds revealed that RAmy1A and GAmyb were highly upregulated in eui aleurone cells in the absence of exogenous GA. In addition, the GA biosynthesis genes GA3ox1 and GA20ox2 were downregulated and GA2ox1 was upregulated in eui seedlings. These results indicate that EUI is involved in GA homeostasis, not only in the internodes at the heading stage, but also in the seedling stage, roots and seeds. Disturbing GA homeostasis affected the expression of the GA signaling genes GID1 (GIBBERELLIN INSENSITIVE DWARF 1), GID2 and SLR1. Transgenic RNA interference of the Eui gene effectively increased plant height and improved heading performance. By contrast, the ectopic expression of Eui under the promoters of the rice GA biosynthesis genes GA3ox2 and GA20ox2 significantly reduced plant height. These results demonstrate that a slight increase in Eui expression could dramatically change rice morphology, indicating the practical application of the Eui gene in rice molecular breeding for a high yield potential.

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Overexpression of a Novel Class of Gibberellin 2-Oxidases Decreases Gibberellin Levels and Creates Dwarf Plants

Cited by 366 publications

References 32 publications

Genetic Analysis Reveals That C19-GA 2-Oxidation Is a Major Gibberellin Inactivation Pathway inArabidopsis

Genetic Analysis Reveals That C19-GA 2-Oxidation Is a Major Gibberellin Inactivation Pathway inArabidopsis

A Novel Dwarfing Mutation in a Green Revolution Gene from Brassica rapa

Gibberellin homeostasis and plant height control by EUI and a role for gibberellin in root gravity responses in rice

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