Two auxin-responsive domains interact positively to induce expression of the early indoleacetic acid-inducible gene PS-IAA4/5.
The plant growth hormone indole-3-acetic acid (IAA) transcriptionally activates expression of several genes in plants. We have previously identified a 164-bp promoter region (-318 to -154) in the PS-IAA4/5 gene that confers IAA inducibility. Linker-scanning mutagenesis across the region has identified two positive domains: domain A (48 bp; -203 to -156) and domain B (44 bp; -299 to -256), responsible for transcriptional activation of PS-IAA4/5 by IAA. Domain A contains the highly conserved sequence 5'-TGTCCCAT-3' found among various IAA-inducible genes and behaves as the major auxin-responsive element. Domain B functions as an enhancer element which may also contain a less efficient auxin-responsive element. The two domains act cooperatively to stimulate transcription; however, tetramerization of domain A or B compensates for the loss of A or B function. The two domains can also mediate IAA-induced transcription from the heterologous cauliflower mosaic virus 35S promoter (-73 to +1). In vivo competition experiments with icosamers of domain A or B show that the domains interact specifically and with different affinities to low abundance, positive transcription factor(s). A model for transcriptional activation of PS-IAA4/5 by IAA is discussed.
Ballas
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Plant Gene Expression Center, Albany, CA 94710, USA.
Wong
L M
LM
Ke
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M
Theologis
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A
D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D004252:DNA Mutational Analysis; D018744:DNA, Plant / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D017343:Genes, Plant / Q000235:genetics*; D017930:Genes, Reporter; D007210:Indoleacetic Acids / Q000378:metabolism / Q000494:pharmacology*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D012097:Repressor Proteins; D013329:Structure-Activity Relationship; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics*; D014158:Transcription, Genetic
D018744:DNA, Plant; D007210:Indoleacetic Acids; D012097:Repressor Proteins; D014157:Transcription Factors; C030737:indoleacetic acid