ACGT-containing abscisic acid response element (ABRE) and coupling element 3 (CE3) are functionally equivalent.
ACGT-containing ABA response elements (ABREs) have been functionally identified in the promoters of various genes. In addition, single copies of ABRE have been found to require a cis-acting, coupling element to achieve ABA induction. A coupling element 3 (CE3) sequence, originally identified as such in the barley HVA1 promoter, is found approximately 30 bp downstream of motif A (ACGT-containing ABRE) in the promoter of the Osem gene. The relationship between these two elements was further defined by linker-scan analyses of a 55 bp fragment of the Osem promoter, which is sufficient for ABA-responsiveness and VP1 activation. The analyses revealed that both motif A and CE3 sequence were required not only for ABA-responsiveness but also for VP1 activation. Since the sequences of motif A and CE3 were found to be similar, motif-exchange experiments were carried out. The experiments demonstrated that motif A and CE3 were interchangeable by each other with respect to both ABA and VP1 regulation. In addition, both sequences were shown to be recognized by a VP1-interacting, ABA-responsive bZIP factor TRAB1. These results indicate that ACGT-containing ABREs and CE3 are functionally equivalent cis-acting elements. Furthermore, TRAB1 was shown to bind two other non-ACGT ABREs. Based on these results, all these ABREs including CE3 are proposed to be categorized into a single class of cis-acting elements.
Hobo
T
T
Center for Molecular Biology and Genetics, Mie University, Kamihama-cho, Japan.
Asada
M
M
Kowyama
Y
Y
Hattori
T
T
D000040:Abscisic Acid / Q000494:pharmacology*; D001483:Base Sequence; D050976:Basic-Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics*; D011485:Protein Binding; D020218:Response Elements; D015534:Trans-Activators; D014157:Transcription Factors / Q000378:metabolism*
D050976:Basic-Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; C094468:Osem protein, Oryza sativa; D010940:Plant Proteins; C403076:TRAB1 protein, plant; D015534:Trans-Activators; D014157:Transcription Factors; D000040:Abscisic Acid