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Arabidopsis basic leucine zipper transcription factors involved in an abscisic acid-dependent signal transduction pathway under drought and high-salinity condition. ABA?. Phytohormone abscisic acid

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  1. Arabidopsis basic leucine zipper transcription factors involved in an abscisic acid-dependent signal transduction pathway under drought and high-salinity condition

  2. ABA? • Phytohormoneabscisic acid • ABA play important roles in vegetative tissues, seed maturation, dormancy to abioticenvironmental stress such as drought , high salimity, cold • ABA promotes with ABI1, ABA2 stomatal closure in the guard cells and regulate the expression of many genes • ABA-inducible gene contain conserved ABRE ABRE(ABA-responsive element) - ABRE(ACGTGGC) in there promoter regions -Function as a cis-acting DNA element involved in ABA-regulated gene expression Specific binding with bZIP protein

  3. -ABREs were first identified in the wheat Em gene ( seed during late embryogenesis) , rice Rab16 gene (expressed in dehydrated vegetative tissues and maturating seed) • -G-box (CACGTG) contein bZIP motif resembles the ABRE motif and functions in the regulation of plant genes in a variety of enviromental conditions (red light, UV light, anaerobiosis, wounding)

  4. ABA Signal Pathway ABI (ABA-Insensitive)1, ABA2 , ERA1 Encode protein phosphatase Key component of signal transduction in Arabidopsis regulate diverse response to the phytohormone abscisic acid Stomatal closure Seed dormancy Inhibition of regulation growth

  5. ABA-related Mutant abi1 : suppressors of non-germination GA-deficient lines phenotype : ABA deficient ; decreased stress or ABA induction of gene expression sugar-resistant seedling growth aba2 : Reduced dormancy phenotype : analogous to abi1 era1 : enhanced response to ABA at germination Expressed in vegetative tissues and are thought to be essential for negative regulation of ABA signaling during vegetative growth

  6. Seedlig germination Root growth Ler wild type Ler wild type abi1 mutant abi1 mutant

  7. wild type abi mutant Under drought stress condition

  8. Water stress Increase in ABA levels ABI1, ABA2 CADPR IP3 Ca2+ release from internal stores Phosphorylation and dephosphorylation events Gene induction ( ex : rd29b, Em, rd16)

  9. AREB1(ABA-Responsive element binding proteins), AREB2, AREB3 • AREB protein contained a sigle bZIP-type DNA-binding domain and upregulated by ABA Function of the AREB proteins in the ABA-dependent signaling pathway in vegetative tissues under dehydration stress condition

  10. Identification of Cis-Acting Elements Involved in Dehydration-Responsive Expression of rd29b

  11. Isolation of cDNAs Encoding DNA-Binding Proteins that Recognize ABRE in the 77-bp DNA Fragment of the rd29B Promoter Control 3-AT ß-gal Fig 2

  12. Structural Analysis of the AREB cDNAs AREB1a AREB2a AREB2 bZIP

  13. Expression of the AREB Genes Dry : 3 weeks NaCl : 250m ABA : 100µM Cold : 4°C

  14. The AREB1 and AREB2 Proteins Transactivate the rd29B Promoter-GUS Fusion Gene in Leaf Protoplasts C: control N: NaCl 250mM 5h D: dehydrate 10h A: ABA 100 µM H: water 5h

  15. Monomer in cultured T87 cell of Arabidopsis

  16. ABA-Specific Phosphorylation of AREB1 and AREB2 Proteins 73G-131Q 84S-133D 335Y-401V RT-PCR Northen blot

  17. Induction of the dehydration-responsive Arabodpsis gene, rd29B, is mediatedmainly ABA • Promoter of rd29B indicated that two ABREs are required for the dehydration-responsive expression of rd29B • Three cDNAs encoding bZIP type AREB1, 2, 3 were isolated by using the yeast one-hybrid system • AREB1,2 gene is up- regulated by drought, NaCl, ABA treatment in vegetative tissues • AREB1,2 proteins activated transcription by ABRE and required ABA for their activation , suppressed by protein kinase inhibitors • phosphorylation is necessary for their maximum activation by ABA, N-term rigion in the AREB proteins

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