title: Isolation and functional characterization of CE1 binding proteins.
abstract: BACKGROUND
  Abscisic acid (ABA) is a plant hormone that controls seed germination, protective responses to various abiotic stresses and seed maturation. The ABA-dependent processes entail changes in gene expression. Numerous genes are regulated by ABA, and promoter analyses of the genes revealed that cis-elements sharing the ACGTGGC consensus sequence are ubiquitous among ABA-regulated gene promoters. The importance of the core sequence, which is generally known as ABA response element (ABRE), has been demonstrated by various experiments, and its cognate transcription factors known as ABFs/AREBs have been identified. Although necessary, ABRE alone is not sufficient, and another cis-element known as "coupling element (CE)" is required for full range ABA-regulation of gene expression. Several CEs are known. However, despite their importance, the cognate transcription factors mediating ABA response via CEs have not been reported to date. Here, we report the isolation of transcription factors that bind one of the coupling elements, CE1.
  
  
  RESULTS
  To isolate CE1 binding proteins, we carried out yeast one-hybrid screens. Reporter genes containing a trimer of the CE1 element were prepared and introduced into a yeast strain. The yeast was transformed with library DNA that represents RNA isolated from ABA-treated Arabidopsis seedlings. From the screen of 3.6 million yeast transformants, we isolated 78 positive clones. Analysis of the clones revealed that a group of AP2/ERF domain proteins binds the CE1 element. We investigated their expression patterns and analyzed their overexpression lines to investigate the in vivo functions of the CE element binding factors (CEBFs). Here, we show that one of the CEBFs, AtERF13, confers ABA hypersensitivity in Arabidopsis, whereas two other CEBFs enhance sugar sensitivity.
  
  
  CONCLUSIONS
  Our results indicate that a group of AP2/ERF superfamily proteins interacts with CE1. Several CEBFs are known to mediate defense or abiotic stress response, but the physiological functions of other CEBFs remain to be determined. Our in vivo functional analysis of several CEBFs suggests that they are likely to be involved in ABA and/or sugar response. Together with previous results reported by others, our current data raise an interesting possibility that the coupling element CE1 may function not only as an ABRE but also as an element mediating biotic and abiotic stress responses.
authors.affiliation: Department of Molecular Biotechnology and Kumho Life Science Laboratory, College of Agriculture and Life Sciences, Chonnam National University, Gwangju 500-757, South Korea.
authors.forename: Sun-ji
authors.initials: SJ
authors.lastname: Lee
authors.forename: Ji Hye
authors.initials: JH
authors.lastname: Park
authors.forename: Mi Hun
authors.initials: MH
authors.lastname: Lee
authors.forename: Ji-hyun
authors.initials: JH
authors.lastname: Yu
authors.forename: Soo Young
authors.initials: SY
authors.lastname: Kim
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005947:Glucose / Q000494:pharmacology; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008856:Microscopy, Fluorescence; D010937:Plant Growth Regulators / Q000494:pharmacology; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D011485:Protein Binding; D034622:RNA Interference; D020218:Response Elements / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D036226:Seedlings / Q000235:genetics / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; C556394:ERF13 protein, Arabidopsis; D008164:Luminescent Proteins; D010937:Plant Growth Regulators; D014157:Transcription Factors; D012965:Sodium Chloride; D000040:Abscisic Acid; D005947:Glucose