Abstract:SummaryThree gibberellin (GA) receptor genes (AtGID1a, AtGID1b and AtGID1c), each an ortholog of the rice GA receptor gene (OsGID1), were cloned from Arabidopsis, and the characteristics of their recombinant proteins were examined. The GA-binding activities of the three recombinant proteins were confirmed by an in vitro assay. Biochemical analyses revealed similar ligand selectivity among the recombinants, and all recombinants showed higher affinity to GA 4 than to other GAs. AtGID1b was unique in its binding … Show more
“…It has previously been shown by semiquantitative RT-PCR that the three genes are expressed in flowers, siliques, stems, leaves, roots, and imbibed seeds at similar levels (Nakajima et al, 2006). However, analysis of the AtGenExpress expression atlas data set (Schmid et al, 2005;www.weigelworld.…”
Section: Expression Of the Arabidopsis Gid1 Genesmentioning
confidence: 99%
“…However, it is not clear whether or how GA-GID1 and SLR1 interaction promotes binding of the GID2 F-box component of the SCF E3 Ub ligase to SLR1. In the Arabidopsis genome, there are three GID1 homologous genes that have been designated: GID1a, GID1b, and GID1c (Nakajima et al, 2006). There is strong evidence to suggest that the proteins they encode function as GA receptors.…”
Section: Introductionmentioning
confidence: 99%
“…Currently, there is no genetic evidence demonstrating a role for the Arabidopsis GID1 genes in GA signaling. However, the three genes display overlapping expression profiles, suggesting that they perform functionally redundant roles (Nakajima et al, 2006).…”
Section: Introductionmentioning
confidence: 99%
“…The molecular mechanisms by which bioactive GAs regulate plant growth and development are less understood, although recent genetic and biochemical studies have identified several key components in GA signaling Sun and Gubler, 2004). The study of GA response in the model plant Arabidopsis thaliana, although fruitful, has been complicated by the high level of functional redundancy within GA signaling components King et al, 2001;Strader et al, 2004;Nakajima et al, 2006). By contrast, several GA signaling components in rice (Oryza sativa) are encoded by single genes, making it a powerful system for studying this pathway.…”
Section: Introductionmentioning
confidence: 99%
“…This is emphasized by a recent study by Ueguchi-Tanaka et al (2005) in which they identified the elusive GA receptor in rice. The identity of the GA receptors provides an important opportunity to dissect the GA signaling cascade in Arabidopsis (Nakajima et al, 2006).…”
We investigated the physiological function of three Arabidopsis thaliana homologs of the gibberellin (GA) receptor GIBBERELLIN-INSENSITIVE DWARF1 (GID1) by determining the developmental consequences of GID1 inactivation in insertion mutants. Although single mutants developed normally, gid1a gid1c and gid1a gid1b displayed reduced stem height and lower male fertility, respectively, indicating some functional specificity. The triple mutant displayed a dwarf phenotype more severe than that of the extreme GA-deficient mutant ga1-3. Flower formation occurred in long days but was delayed, with severe defects in floral organ development. The triple mutant did not respond to applied GA. All three GID1 homologs were expressed in most tissues throughout development but differed in expression level. GA treatment reduced transcript abundance for all three GID1 genes, suggesting feedback regulation. The DELLA protein REPRESSOR OF ga1-3 (RGA) accumulated in the triple mutant, whose phenotype could be partially rescued by loss of RGA function. Yeast two-hybrid and in vitro pull-down assays confirmed that GA enhances the interaction between GID1 and DELLA proteins. In addition, the N-terminal sequence containing the DELLA domain is necessary for GID1 binding. Furthermore, yeast three-hybrid assays showed that the GA-GID1 complex promotes the interaction between RGA and the F-box protein SLY1, a component of the SCF SLY1 E3 ubiquitin ligase that targets the DELLA protein for degradation.
“…It has previously been shown by semiquantitative RT-PCR that the three genes are expressed in flowers, siliques, stems, leaves, roots, and imbibed seeds at similar levels (Nakajima et al, 2006). However, analysis of the AtGenExpress expression atlas data set (Schmid et al, 2005;www.weigelworld.…”
Section: Expression Of the Arabidopsis Gid1 Genesmentioning
confidence: 99%
“…However, it is not clear whether or how GA-GID1 and SLR1 interaction promotes binding of the GID2 F-box component of the SCF E3 Ub ligase to SLR1. In the Arabidopsis genome, there are three GID1 homologous genes that have been designated: GID1a, GID1b, and GID1c (Nakajima et al, 2006). There is strong evidence to suggest that the proteins they encode function as GA receptors.…”
Section: Introductionmentioning
confidence: 99%
“…Currently, there is no genetic evidence demonstrating a role for the Arabidopsis GID1 genes in GA signaling. However, the three genes display overlapping expression profiles, suggesting that they perform functionally redundant roles (Nakajima et al, 2006).…”
Section: Introductionmentioning
confidence: 99%
“…The molecular mechanisms by which bioactive GAs regulate plant growth and development are less understood, although recent genetic and biochemical studies have identified several key components in GA signaling Sun and Gubler, 2004). The study of GA response in the model plant Arabidopsis thaliana, although fruitful, has been complicated by the high level of functional redundancy within GA signaling components King et al, 2001;Strader et al, 2004;Nakajima et al, 2006). By contrast, several GA signaling components in rice (Oryza sativa) are encoded by single genes, making it a powerful system for studying this pathway.…”
Section: Introductionmentioning
confidence: 99%
“…This is emphasized by a recent study by Ueguchi-Tanaka et al (2005) in which they identified the elusive GA receptor in rice. The identity of the GA receptors provides an important opportunity to dissect the GA signaling cascade in Arabidopsis (Nakajima et al, 2006).…”
We investigated the physiological function of three Arabidopsis thaliana homologs of the gibberellin (GA) receptor GIBBERELLIN-INSENSITIVE DWARF1 (GID1) by determining the developmental consequences of GID1 inactivation in insertion mutants. Although single mutants developed normally, gid1a gid1c and gid1a gid1b displayed reduced stem height and lower male fertility, respectively, indicating some functional specificity. The triple mutant displayed a dwarf phenotype more severe than that of the extreme GA-deficient mutant ga1-3. Flower formation occurred in long days but was delayed, with severe defects in floral organ development. The triple mutant did not respond to applied GA. All three GID1 homologs were expressed in most tissues throughout development but differed in expression level. GA treatment reduced transcript abundance for all three GID1 genes, suggesting feedback regulation. The DELLA protein REPRESSOR OF ga1-3 (RGA) accumulated in the triple mutant, whose phenotype could be partially rescued by loss of RGA function. Yeast two-hybrid and in vitro pull-down assays confirmed that GA enhances the interaction between GID1 and DELLA proteins. In addition, the N-terminal sequence containing the DELLA domain is necessary for GID1 binding. Furthermore, yeast three-hybrid assays showed that the GA-GID1 complex promotes the interaction between RGA and the F-box protein SLY1, a component of the SCF SLY1 E3 ubiquitin ligase that targets the DELLA protein for degradation.
Since their discovery, gibberellin (GA) diterpenoid phytohormones have been used by agriculturalists and horticulturalists to control plant growth and to improve yield quantity and quality. Coordinated breeding efforts after World War II have led to strong yield increases following the introduction of dwarfing alleles that impair GA signalling in wheat and GA biosynthesis in rice, later named the ‘Green Revolution’. In the last two decades, the identity of the basic components of the GA signal transduction pathway has been elucidated. Core to GA action is the regulation of DELLA protein levels, repressors that control plant growth by negatively interfering mainly, but as it emerges not exclusively, with transcription regulator activities. Here, the author summarises the current knowledge of GA signal transduction, thereby putting an emphasis on the crosstalk of GA signalling with the light and jasmonic acid signalling pathways and with microtubule organisation.
Key Concepts:
Manipulation of gibberellin (GA) signalling has contributed to the ‘Green Revolution’.
DELLA proteins are GA‐labile growth repressors that mainly, but not exclusively, repress transcription factors.
GA inactivates DELLAs by targeting them for degradation by the ubiquitin–proteasome system.
Alternative GA‐independent DELLA inactivation mechanisms have been described.
GA and DELLAs repress PIF and BZR1 transcription factors to control light‐regulated development.
GA and DELLAs antagonistically control different steps in the signal transduction of the phytohormone jasmonic acid.
GA and DELLAs modulate microtubule formation by modulating prefoldin activity.
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