title: A novel abi5 allele reveals the importance of the conserved Ala in the C3 domain for regulation of downstream genes and salt tolerance during germination in Arabidopsis.
abstract: Abscisic acid (ABA) signal transduction during Arabidopsis seed development and germination requires a Group A bZIP transcription factor encoded by ABA INSENSITIVE5 (ABI5). In addition to the basic leucine zipper DNA binding domain, Group A bZIPs are characterized by three N-terminal conserved regions (C1, C2 and C3) and one C-terminal conserved region (C4). These conserved regions are considered to play roles in ABI5 functions; however, except for the phosphorylation site, the importance of the highly conserved amino acids is unclear. Here, we report a novel abi5 recessive allele (abi5-9) that encodes an intact ABI5 protein with one amino acid substitution (A214G) in the C3 domain. The abi5-9 plants showed ABA insensitivity during germination and could germinate on medium containing 175 mM NaCl or 500 mM mannitol. Em1 and Em6--both encoding late embryogenesis abundant (LEA) proteins and directly targeted by ABI5 regulation--were expressed at very low levels in abi5-9 plants compared with the wild type. In yeast, the abi5-9 protein exhibited greatly reduced interaction with ABI3 compared with ABI5. These data suggest that Ala214 in ABI5 contributes to the function of ABI5 via its interaction with ABI3.
authors.affiliation: Department of BioScience; Tokyo University of Agriculture; Tokyo, Japan; Department of Applied Biology and Chemistry; Faculty of Applied Biosciences; Tokyo University of Agriculture; Tokyo, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Tezuka
authors.forename: Teruaki
authors.initials: T
authors.lastname: Taji
authors.forename: Takahisa
authors.initials: T
authors.lastname: Hayashi
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Sakata
mesh_terms: D000040:Abscisic Acid / Q000235:genetics* / Q000378:metabolism; D000409:Alanine / Q000378:metabolism; D000483:Alleles; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D050976:Basic-Leucine Zipper Transcription Factors / Q000235:genetics* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005838:Genotype; D018525:Germination / Q000235:genetics*; D016350:Leucine Zippers; D009154:Mutation; D030821:Plants, Genetically Modified; D017434:Protein Structure, Tertiary; D055049:Salt Tolerance / Q000235:genetics*; D012639:Seeds; D015398:Signal Transduction
chemical_list: C409743:ABI5 protein, Arabidopsis; D029681:Arabidopsis Proteins; D050976:Basic-Leucine Zipper Transcription Factors; D000040:Abscisic Acid; D000409:Alanine
keywords: ABA; abiotic stress tolerance; abscisic acid; gene expression; growth control; hormone signaling; plant signaling; transcriptional regulation