RT Journal Article
SR Electronic
T1 AUX/IAA Proteins Are Active Repressors, and Their Stability and Activity Are Modulated by Auxin
JF The Plant Cell
JO Plant Cell
FD American Society of Plant Biologists
SP 2809
OP 2822
DO 10.1105/tpc.010289
VO 13
IS 12
A1 Tiwari, Shiv B.
A1 Wang, Xiao-Jun
A1 Hagen, Gretchen
A1 Guilfoyle, Tom J.
YR 2001
UL http://www.plantcell.org/content/13/12/2809.abstract
AB Aux/IAA genes are early auxin response genes that encode short-lived nuclear proteins with four conserved domains, referred to as I, II, III, and IV. Arabidopsis Aux/IAA proteins repressed transcription on auxin-responsive reporter genes in protoplast transfection assays. Mutations in domain II resulted in increased repression, whereas mutations in domains I and III partially relieved repression. Aux/IAA proteins fused to a heterologous DNA binding domain were targeted to promoters of constitutively expressed reporter genes and actively repressed transcription in an auxin-responsive and dose-dependent manner. In comparison with an unfused luciferase protein, luciferase fused to Aux/IAA proteins displayed less luciferase activity, which further decreased in the presence of auxin in transfected protoplasts. Domain II mutations increased and domain I mutations decreased luciferase activity with the fusion proteins. These results suggested that Aux/IAA proteins function as active repressors by dimerizing with auxin response factors bound to auxin response elements and that early auxin response genes are regulated by auxin-modulated stabilities of Aux/IAA proteins.