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Regulation of Arabidopsis TGA transcription factors by cysteine residues : implication for redox controlChubak, Catherine 26 May 2006
The Arabidopsis TGA family of basic leucine zipper transcription factors regulate the expression of pathogenesis-related genes and are required for resistance to disease. Members of the family possess diverse properties in respect to their ability to transactivate and interact with NPR1, the central regulator of systemic acquired resistance in Arabidopsis. Two TGA factors, TGA1 and TGA2, have 83 % amino acid similarity but possess differing properties. TGA1 does not interact with NPR1 but is able to transactivate, while TGA2 interacts with NPR1 but is unable to transactivate. This study uses these two TGA factors to identify amino acids that are responsible for their function. <p>Four cysteines residues within TGA1 were targeted for study by site-directed mutagenesis and the resulting mutants were tested for interaction with NPR1 in yeast. The construct containing a mutation of cysteine 260 (Cys-260) interacted well with NPR1, while those with mutations at Cys-172 or Cys-266 interacted poorly. The Cys-260 mutant also displayed the greatest decrease in transactivation potential in yeast, while mutation of Cys-172 or Cys-266 resulted in smaller decreases. Mutation of Cys-287 had no effect on NPR1 interaction or transactivation. Combining various point mutations in a single protein did not increase NPR1 interaction or transactivation levels, indicating that Cys-260 is crucial for regulating TGA1 properties. Cysteines possess the unique ability of forming reversible disulfide bonds which have been shown to regulate several mammalian cellular processes. The observation that mutation of a single TGA1 cysteine (Cys-260) greatly alters the proteins properties provides a convincing argument that oxidoreduction of this residue is important for its regulation, possibly through the formation of a disulfide bond with either Cys-172 or Cys-266. <p>To test whether other members of the TGA family could be regulated by oxidoreduction, several TGA2 constructs were created that introduced Cys at positions corresponding to those found in TGA1. When tested in yeast none were able to transactivate but continued to interact with NPR1.
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Regulation of Arabidopsis TGA transcription factors by cysteine residues : implication for redox controlChubak, Catherine 26 May 2006 (has links)
The Arabidopsis TGA family of basic leucine zipper transcription factors regulate the expression of pathogenesis-related genes and are required for resistance to disease. Members of the family possess diverse properties in respect to their ability to transactivate and interact with NPR1, the central regulator of systemic acquired resistance in Arabidopsis. Two TGA factors, TGA1 and TGA2, have 83 % amino acid similarity but possess differing properties. TGA1 does not interact with NPR1 but is able to transactivate, while TGA2 interacts with NPR1 but is unable to transactivate. This study uses these two TGA factors to identify amino acids that are responsible for their function. <p>Four cysteines residues within TGA1 were targeted for study by site-directed mutagenesis and the resulting mutants were tested for interaction with NPR1 in yeast. The construct containing a mutation of cysteine 260 (Cys-260) interacted well with NPR1, while those with mutations at Cys-172 or Cys-266 interacted poorly. The Cys-260 mutant also displayed the greatest decrease in transactivation potential in yeast, while mutation of Cys-172 or Cys-266 resulted in smaller decreases. Mutation of Cys-287 had no effect on NPR1 interaction or transactivation. Combining various point mutations in a single protein did not increase NPR1 interaction or transactivation levels, indicating that Cys-260 is crucial for regulating TGA1 properties. Cysteines possess the unique ability of forming reversible disulfide bonds which have been shown to regulate several mammalian cellular processes. The observation that mutation of a single TGA1 cysteine (Cys-260) greatly alters the proteins properties provides a convincing argument that oxidoreduction of this residue is important for its regulation, possibly through the formation of a disulfide bond with either Cys-172 or Cys-266. <p>To test whether other members of the TGA family could be regulated by oxidoreduction, several TGA2 constructs were created that introduced Cys at positions corresponding to those found in TGA1. When tested in yeast none were able to transactivate but continued to interact with NPR1.
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Functional Analysis of the Salicylic Acid-Responsive PR-1 Promoter in Arabidopsis thaliana / Funktionale Analyse des Salicylsäure-induzierbaren PR-1 Promotors in Arabidopsis thalianaPape, Sebastian 09 July 2009 (has links)
No description available.
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Subcellular Localization of Nicotiana tabacum TGA Transcription Factors / Subzelluläre Lokalisation von TGA Transkriptionfaktoren aus Nicotiana tabacumNickolov, Kaloian Iliev 30 January 2003 (has links)
Die Salicylsäure (SA) ist ein wichtiges Signalmolekül bei der Regulation der pflanzlichen Pathogenabwehr. as-1-ähnliche cis-Elemente in den Promotoren von vielen Abwehrgenen vermitteln SA- und auch Auxin-induzierbare Genexpression. Diese Elemente werden vom ASF-1/SARP-Proteinkomplex erkannt, dessen Hauptkomponenten DNA-Bindeproteine aus der TGA-Familie der pflanzlichen bZIP-Transkriptionsfaktoren sind. In dieser Arbeit wurden Fusionsproteine von TGA2.1, TGA2.2 und TGA1a mit GFP unter der Kontrolle des HBT-Promotors transient in Pflanzenprotoplasten oder stabil in transgenen Pflanzen exprimiert und direkt in lebenden Zellen über Fluoreszenz- und konfokale Laser-Scanning-Mikroskopie visualisiert. Bei den mikroskopischen Analysen konnte die Fluoreszenz der drei TGA-GFP-Fusionsproteine überwiegend im Kern (mit Ausnahme des Nukleolus) beobachtet werden. Allerdings ließen sich biochemisch mit Hilfe eines Antiserums gegen die beiden C Termini der TGA-Faktoren auch geringe Mengen von TGA2.1-GFP und TGA2.2-GFP in cytosolischen Extrakten der entsprechenden transgenen Pflanzen nachweisen. Fusionen der C terminalen Anteile von TGA2.2 und TGA1a an den C Terminus von CHS-GFP wurden bei transienter Expression ebenfalls im Cytosol beobachtet. Es konnte nicht abschließend geklärt werden, ob dass auf das Fehlen der NLS oder auf die Anwesenheit einer NES zurück zu führen ist. Die TGA-GFP-Fusionsproteine konnten das as 1-Element in vitro in Gelretardationsanalysen erkennen und in Form von Homo-oder Heterodimeren daran binden. Die TGA-GFP-Fusionsproteine waren auch in der Lage, die Expression des frühen (immediate-early) GST-Gens Nt103 in Blättern nach Induktion mit Salicylsäure oder Auxin zu beeinflussen. TGA2.1-GFP und TGA2.2-GFP zeigten im allgemeinen einen positiven Effekt auf die Nt103-mRNA-Menge (2-4-facher Anstieg verglichen mit dem Wildtyp), wobei sich der Effekt stärker auf die SA-induzierte Expression auswirkte als auf die 2,4-D-Proben. TGA1a-GFP schien die Expression von Nt103 in Blättern in beiden Fällen leicht negativ oder gar nicht zu beeinflussen. Die Mobilitätsparameter der verschiedenen TGA-GFP-Fusionsproteine im Kern wurden mit Hilfe von FCS, kombiniert mit CLMS, untersucht. Während die Mobilität des Kontrollproteins TetR-GFP, dass keine endogenen Interaktionpartner hat, einheitlich war, schienen Subfraktionen der TGA-GFP Fusionproteine in ihrer Mobilität beeinflusst. Generell konnte zwischen einer mobileren und einer weniger mobilen Fraktion unterschieden werden. Bei manchen Messungen waren die TGA-Faktoren im Kern sogar gänzlich immobil. Die relative Anteil von weniger mobilen, bzw. immobilen und mobilen TGA-faktoren unterschied sich in den unterschiedlichen analysierten Zelltypen (längliche und echte Epidermiszellen, Schießzellen, Trichomzellen). Um einen eindeutigen Effekt von Salizylsäure auf die Mobilität der TGA-Faktoren festzumachen, sind wegen der großen Variabilität weitere Messungen nötig.
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Arabidopsis thaliana class II TGA transcription factors provide a molecular link between salicylic acid and ethylene defense signalling / Arabidopsis thaliana Klasse II TGA-Transkriptionsfaktoren verbinden den Salicylsäure- mit dem Ethylen-SignalwegZander, Mark 27 April 2011 (has links)
No description available.
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