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.
Center for Agricultural Biotechnology, University of Maryland, College Park, Maryland 20742, USA.
P
P
Pascuzzi
D
D
Hamilton
K
K
Bodily
J
J
Arias
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