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
- ABA play important roles in vegetative tissues, seed maturation, dormancy to abiotic environmental 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
Specific binding with bZIP protein
- ABRE(ACGTGGC) in there promoter regions
-Function as a cis-acting DNA element involved in ABA-regulated gene expression
ABRE(ABA-responsive element)
-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)
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
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
ABA-related Mutant
Ler wild type
abi1 mutant
Seedlig germination Root growth
Ler wild type
abi1 mutant
abi mutantwild type
Under drought stress condition
Water stress
Increase in ABA levels
CADPR IP3
Ca2+ release from internal stores
Phosphorylation and dephosphorylation events
Gene induction ( ex : rd29b, Em, rd16)
ABI1, ABA2
AREB1(ABA-Responsive element binding proteins), AREB2, AREB3
-AREB protein contained a sigle bZIP-type DNA-binding domain and up regulated by ABA
Function of the AREB proteins in the ABA-dependent signaling pathway in vegetative tissues under dehydration stress condition
Identification of Cis-Acting Elements Involved in Dehydration-Responsive Expression of rd29b
Isolation of cDNAs Encoding DNA-Binding Proteins that Recognize ABRE in the 77-bp DNA Fragment of the rd29B Promoter
Control 3-AT ß-galFig 2
Structural Analysis of the AREB cDNAs AREB1aAREB2a
AREB2 bZIP
Expression of the AREB Genes
Dry : 3 weeks NaCl : 250m
ABA : 100µM Cold : 4°C
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
Monomer in cultured T87 cell of Arabidopsis
ABA-Specific Phosphorylation of AREB1 and AREB2 Proteins
73G-131Q
84S-133D
335Y-401V
Northen blot
RT-PCR
-Induction of the dehydration-responsive Arabodpsis gene, rd29B, is mediated mainly 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