Auxin-induced stress potentiates trans-activation by a conserved plant basic/leucine-zipper factor.
The promoter element activation sequence-1 (as-1) confers tissue-specific and signal-responsive transcription in plants. Hormone and chemical stress cues are thought to activate as-1-dependent transcription through specific basic/leucine-zipper proteins, termed TGA factors, that bind this element. We report here that a highly conserved TGA factor of tobacco, TGA1a, can selectively activate transcription in response to micromolar concentrations of auxin hormones or their analogs. This induction is chemically specific, as a range of other compounds tested at similar concentrations had little or no effect. Auxin was found to augment the trans-activation potential of TGA1a through carboxyl-terminal residues. The amino-terminal domain of TGA1a, by gain-of-function assays, was found to both constitutively activate transcription and maximize the response to auxin. Further evidence indicates that the trans-activation potential of this domain in TGA1a is repressed, under basal conditions, by carboxyl-terminal residues. Because TGA1a and endogenous TGA factors are stimulated by auxin only at concentrations that inhibited cell growth, this response is likely to involve chemical stress.
Pascuzzi
P
P
Center for Agricultural Biotechnology, University of Maryland, College Park, Maryland 20742, USA.
Hamilton
D
D
Bodily
K
K
Arias
J
J
D050976:Basic-Leucine Zipper Transcription Factors; D002478:Cells, Cultured; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism*; D016350:Leucine Zippers; D010940:Plant Proteins / Q000378:metabolism; D010947:Plants, Toxic; D014026:Nicotiana / Q000166:cytology / Q000378:metabolism*; D015533:Transcriptional Activation / Q000502:physiology*
D050976:Basic-Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; D007210:Indoleacetic Acids; D010940:Plant Proteins; C065794:TGA1a protein, Nicotiana tabacum; D015500:Chloramphenicol O-Acetyltransferase