age Mutants of Arabidopsis Exhibit Altered Auxin-Regulated Gene Expression

Oono, Yutaka; Chen, Qianhong G.; Overvoorde, Paul J.; Köhler, Claudia; Theologis, Athanasios

doi:10.2307/3870763

Cited by 37 publications

(74 citation statements)

References 41 publications

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“…The Arabidopsis BA3 line containing the ␤-glucuronidase (GUS) reporter under the regulatory control of an auxinresponsive synthetic promoter derived from the Pisum sativum PS-IAA4͞5 gene provided a necessary tool for such a screening strategy. This system was previously used to identify the auxinhypersensitive mutant lines age1 and age2 (24). The power of transcriptional profiling has been harnessed to dissect the early modulations of gene expression induced by auxin treatment (25,26).…”

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confidence: 99%

Identification of inhibitors of auxin transcriptional activation by means of chemical genetics in Arabidopsis

Armstrong

Yuan

Dale

et al. 2004

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

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Auxin modulates diverse plant developmental pathways through direct transcriptional regulation and cooperative signaling with other plant hormones. Genetic and biochemical approaches have clarified several aspects of the auxin-regulated networks; however, the mechanisms of perception and subsequent signaling events remain largely uncharacterized. To elucidate unidentified intermediates, we have developed a high-throughput screen for identifying small molecule inhibitors of auxin signaling in Arabidopsis . Analysis of 10,000 compounds revealed several potent lead structures that abrogate transcription of an auxin-inducible reporter gene. Three compounds were found to interfere with auxin-regulated proteolysis of an auxin/indole-3-acetic acid transcription factor, and two impart phenotypes indicative of an altered auxin response, including impaired root development. Microarray analysis was used to demonstrate the mechanistic similarities of the two most potent molecules. This strategy promises to yield powerful tools for the discovery of unidentified components of the auxin-signaling networks and the study of auxin's participation in various stages of plant development.

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confidence: 99%

Identification of inhibitors of auxin transcriptional activation by means of chemical genetics in Arabidopsis

Armstrong

Yuan

Dale

et al. 2004

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

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“…26. After centrifugation to remove cell debris, GUS activity was measured with 1 mM 4-methyl umbelliferyl ␤-D-glucuronide as a substrate at 37°C.…”

Section: Methodsmentioning

confidence: 99%

Yokonolide B, a Novel Inhibitor of Auxin Action, Blocks Degradation of AUX/IAA Factors

Hayashi

Jones

Ogino

et al. 2003

Journal of Biological Chemistry

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Yokonolide B (YkB; also known as A82548A), a spiroketal-macrolide, was isolated from Streptomyces diastatochromogenes B59 in a screen for inhibitors of ␤-glucoronidase expression under the control of an auxin-responsive promoter in Arabidopsis. YkB inhibits the expression of auxin-inducible genes as shown using native and synthetic auxin promoters as well as using expression profiling of 8,300 Arabidopsis gene probes but does not affect expression of an abscisic acid-and a gibberellin A 3 -inducible gene. The mechanism of action of YkB is to block AUX/IAA protein degradation; however, YkB is not a general proteasome inhibitor. YkB blocks auxin-dependent cell division and auxin-regulated epinastic growth mediated by auxin-binding protein 1. Gain of function mutants such as shy2-2, slr1, and axr2-1 encoding AUX/IAA transcriptional repressors and loss of function mutants encoding components of the ubiquitin-proteolytic pathway such as axr1-3 and tir1-1, which display increased AUX/IAAs protein stability, are less sensitive to YkB, although axr1 and tir1 mutants were sensitive to MG132, a general proteasome inhibitor, consistent with a site of action downstream of AXR1 and TIR. YkB-treated seedlings displayed similar phenotypes as dominant AUX/IAA mutants. Taken together, these results indicate that YkB acts to block AUX/IAA protein degradation upstream of AXR and TIR, links a shared element upstream of AUX/IAA protein stability to auxin-induced cell division/elongation and to auxin-binding protein 1, and provides a new tool to dissect auxin signal transduction.Auxin controls cell division, elongation, and differentiation and therefore, through its action at the level of the cell, exerts profound effects on growth and development throughout the life of the plant (1). Consistent with the diverse effects of auxin on growth and development is that the expression patterns of a number of genes are dramatically and rapidly altered by auxin application (2), suggesting that auxin ultimately regulates cell growth by controlling the profile of expressed genes. AUX/IAA genes comprise a 34-member gene family in Arabidopsis that is one of three known gene families that are regulated by auxin and implicated to play essential roles in auxin signaling (3, 4).The molecular and genetic studies on auxin signaling have revealed that auxin specifically enhances the transcription of many AUX/IAA genes within minutes without requiring de novo protein synthesis, suggesting that AUX/IAA genes are primary auxin-response genes (5, 6). AUX/IAA genes encode short lived nuclear proteins capable of heterodimerization with auxin-responsive factors (7) and are thought to act by negatively regulating the expression of early auxin-responsive genes including other members of the AUX/IAA family (3).Studies on Arabidopsis mutants with altered responses to auxin such as iaa3/shy2-2, iaa7/axr2-1, iaa17/axr3, iaa14/slr1, tir1, and axr1 revealed that the turnover rate of AUX/IAA proteins is in some way important in various developmental processes including ...

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“…For the histochemical GUS assay, the seedlings were washed with buffer A [100 mM sodium phosphate, pH 7.0͞10 mM EDTA͞0.5 mM K 3 Fe(CN) 6 ͞0.1% Triton X-100] and then incubated in a staining buffer (buffer A with 1 mM 5-bromo-4-chloro-3-indolyl ␤-D-glucuronide) at 37°C until sufficient staining developed (11). For quantitative fluorometric GUS assays, whole seedlings (n ϭ 10-20) were homogenized in an extraction buffer as described in ref.…”

Section: Gus Activity Measurementmentioning

confidence: 99%

“…For quantitative fluorometric GUS assays, whole seedlings (n ϭ 10-20) were homogenized in an extraction buffer as described in ref. 11. After centrifugation to remove cell debris, GUS activity was measured with 1 mM 4-methyl umbelliferyl ␤-D-glucuronide as a substrate at 37°C (11).…”

Section: Gus Activity Measurementmentioning

confidence: 99%

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Genetic and chemical analyses of the action mechanisms of sirtinol in Arabidopsis

Dai

Hayashi²,

Nozaki³

et al. 2005

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

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The synthetic molecule sirtinol was shown previously to activate the auxin signal transduction pathway. Here we present a combination of genetic and chemical approaches to elucidate the action mechanisms of sirtinol in Arabidopsis. Analysis of sirtinol derivatives indicated that the ''active moiety'' of sirtinol is 2-hydroxy-1-naphthaldehyde (HNA), suggesting that sirtinol undergoes a series of transformations in Arabidopsis to generate HNA, which then is converted to 2-hydroxy-1-naphthoic acid (HNC), which activates auxin signaling. A key step in the activation of sirtinol is the conversion of HNA to HNC, which is likely catalyzed by an aldehyde oxidase. Mutations in any of the genes that are responsible for synthesizing the molybdopterin cofactor, an essential cofactor for aldehyde oxidases, led to resistance to sirtinol, probably caused by the compromised capacity of the mutants to convert HNA to HNC. We also showed that sirtinol and HNA could bypass the auxin polar transport system and that they were transported efficiently to aerial parts of seedlings, whereas HNC and 1-naphthoic acid were essentially not absorbed by Arabidopsis seedlings, suggesting that sirtinol and HNA are useful tools for auxin studies.auxin ͉ polar transport ͉ molybdopterin ͉ aldehyde oxidase

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age Mutants of Arabidopsis Exhibit Altered Auxin-Regulated Gene Expression

Cited by 37 publications

References 41 publications

Identification of inhibitors of auxin transcriptional activation by means of chemical genetics in Arabidopsis

Identification of inhibitors of auxin transcriptional activation by means of chemical genetics in Arabidopsis

Yokonolide B, a Novel Inhibitor of Auxin Action, Blocks Degradation of AUX/IAA Factors

Genetic and chemical analyses of the action mechanisms of sirtinol in Arabidopsis

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