Evidence that the <i>Arabidopsis</i> nuclear gibberellin signalling protein GAI is not destabilised by gibberellin

Fleck, Barbara; Harberd, Nicholas P.

doi:10.1046/j.1365-313x.2002.01478.x

Cited by 82 publications

(75 citation statements)

References 45 publications

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“…In this article, we demonstrate that SLY1 interacts not only with RGA, but also with GAI through their GRAS domains. In contrast with a previous study (Fleck and Harberd, 2002), we show that GA induces degradation of the endogenous GAI protein and that the sly1-10 mutant accumulates a significantly higher amount of GAI than in the wild type. The rga and gai null alleles synergistically suppress several GA-mediated processes in sly1-10.…”

Section: Introductioncontrasting

confidence: 99%

“…Although a previous study showed that levels of a GAI-GFP fusion were not reduced by GA treatment (Fleck and Harberd, 2002), we decided to use immunoblot analysis to examine whether endogenous GAI protein level is elevated in the sly1-10 mutant background and whether GA treatment induces a rapid reduction in GAI protein levels in the wild-type SLY1 background. The predicted molecular masses of RGA and GAI are 64 and 59 kD, respectively.…”

Section: Regulation Of Ga-induced Gai Degradation By Sly1mentioning

confidence: 99%

“…These results suggest that the N-terminal DELLA and VHYNP motifs are essential in the GA-induced degradation of these DELLA proteins. However, GFP protein fusions with RGL1 or GAI were reported to remain stable after GA treatment (Fleck and Harberd, 2002;Wen and Chang, 2002), suggesting that GA may regulate other DELLA proteins via different mechanisms.…”

Section: Introductionmentioning

confidence: 99%

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The Arabidopsis F-Box Protein SLEEPY1 Targets Gibberellin Signaling Repressors for Gibberellin-Induced Degradation[W]

et al. 2004

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The nuclear DELLA proteins are highly conserved repressors of hormone gibberellin (GA) signaling in plants. In Arabidopsis thaliana, GA derepresses its signaling pathway by inducing proteolysis of the DELLA protein REPRESSOR OF ga1-3 (RGA). SLEEPY1 (SLY1) encodes an F-box-containing protein, and the loss-of-function sly1 mutant has a GA-insensitive dwarf phenotype and accumulates a high level of RGA. These findings suggested that SLY1 recruits RGA to the SCF SLY1 E3 ligase complex for ubiquitination and subsequent degradation by the 26S proteasome. In this report, we provide new insight into the molecular mechanism of how SLY1 interacts with the DELLA proteins for controlling GA response. By yeast two-hybrid and in vitro pull-down assays, we demonstrated that SLY1 interacts directly with RGA and GA INSENSITIVE (GAI, a closely related DELLA protein) via their C-terminal GRAS domain. The rga and gai null mutations additively suppressed the recessive sly1 mutant phenotype, further supporting the model that SCF SLY1 targets both RGA and GAI for degradation. The N-terminal DELLA domain of RGA previously was shown to be essential for GA-induced degradation. However, we found that this DELLA domain is not required for protein-protein interaction with SLY1 in yeast (Saccharomyces cerevisiae), suggesting that its role is in a GA-triggered conformational change of the DELLA proteins. We also identified a novel gainof-function sly1-d mutation that increased GA signaling by reducing the levels of the DELLA protein in plants. This effect of sly1-d appears to be caused by an enhanced interaction between sly1-d and the DELLA proteins.

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Section: Introductioncontrasting

confidence: 99%

Section: Regulation Of Ga-induced Gai Degradation By Sly1mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Arabidopsis F-Box Protein SLEEPY1 Targets Gibberellin Signaling Repressors for Gibberellin-Induced Degradation[W]

et al. 2004

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“…GA relieves DELLA restraint by promoting the disappearance of nuclear DELLAs (Silverstone et al, 2001;Fleck and Harberd, 2002). In Arabidopsis, GA is detected by the GA receptor AtGID1 (Nakajima et al, 2006).…”

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confidence: 99%

DELLAs Contribute to Plant Photomorphogenesis

et al. 2007

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Plant morphogenesis is profoundly influenced by light (a phenomenon known as photomorphogenesis). For example, light inhibits seedling hypocotyl growth via activation of phytochromes and additional photoreceptors. Subsequently, information is transmitted through photoreceptor-linked signal transduction pathways and used (via previously unknown mechanisms) to control hypocotyl growth. Here we show that light inhibition of Arabidopsis (Arabidopsis thaliana) hypocotyl growth is in part dependent on the DELLAs (a family of nuclear growth-restraining proteins that mediate the effect of the phytohormone gibberellin [GA] on growth). We show that light inhibition of growth is reduced in DELLA-deficient mutant hypocotyls. We also show that light activation of phytochromes promotes the accumulation of DELLAs. A green fluorescent protein (GFP)-tagged DELLA (GFP-RGA) accumulates in elongating cells of light-grown, but not dark-grown, transgenic wild-type hypocotyls. Furthermore, transfer of seedlings from light to dark (or vice versa) results in rapid changes in hypocotyl GFP-RGA accumulation, changes that are paralleled by rapid alterations in the abundance in hypocotyls of transcripts encoding enzymes of GA metabolism. These observations suggest that light-dependent changes in hypocotyl GFP-RGA accumulation are a consequence of light-dependent changes in bioactive GA level. Finally, we show that GFP accumulation and quantitative modulation of hypocotyl growth is proportionate with light energy dose (the product of exposure duration and fluence rate). Hence, DELLAs inhibit hypocotyl growth during the light phase of the day-night cycle via a mechanism that is quantitatively responsive to natural light variability. We conclude that DELLAs are a major component of the adaptively significant mechanism via which light regulates plant growth during photomorphogenesis.

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“…In addition, one or two putative nuclear localization signals are present in some of the GRAS members, suggesting that they may function as transcriptional regulators (Pysh et 1999). Indeed, several DELLA proteins, when fused with the green fluorescence protein, are localized to the nuclei in transgenic plants (Silverstone et al, 2001;Fleck and Harberd, 2002;Gubler et al, 2002;Itoh et al, 2002;Wen and Chang, 2002).…”

mentioning

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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Evidence that the Arabidopsis nuclear gibberellin signalling protein GAI is not destabilised by gibberellin

Cited by 82 publications

References 45 publications

The Arabidopsis F-Box Protein SLEEPY1 Targets Gibberellin Signaling Repressors for Gibberellin-Induced Degradation[W]

The Arabidopsis F-Box Protein SLEEPY1 Targets Gibberellin Signaling Repressors for Gibberellin-Induced Degradation[W]

DELLAs Contribute to Plant Photomorphogenesis

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

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