RAC GTPases in tobacco and Arabidopsis mediate auxin-induced formation of proteolytically active nuclear protein bodies that contain AUX/IAA proteins.
Auxin signaling relies on ubiquitin ligase SCF(TIR1)-mediated 26S proteasome-dependent proteolysis of a large family of short-lived transcription regulators, auxin/indole acetic acid (Aux/IAA), resulting in the derepression of auxin-responsive genes. We have shown previously that a subset of Rac GTPases is activated by auxin, and they in turn stimulate auxin-responsive gene expression. We show here that increasing Rac signaling activity promotes Aux/IAA degradation, whereas downregulating that activity results in the reduction of auxin-accelerated Aux/IAA proteolysis. Observations reported here reveal a novel function for these Rac GTPases as regulators for ubiquitin/26S proteasome-mediated proteolysis and further consolidate their role in auxin signaling. Moreover, our study reveals a cellular process whereby auxin induces and Rac GTPases mediate the recruitment of nucleoplasmic Aux/IAAs into proteolytically active nuclear protein bodies, into which components of the SCF(TIR1), COP9 signalosome, and 26S proteasome are also recruited.
Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003, USA.
Li-Zhen
LZ
Tao
Alice Y
AY
Cheung
Candida
C
Nibau
Hen-Ming
HM
Wu
D029681:Arabidopsis Proteins / Q000378:metabolism*; D017930:Genes, Reporter; D007210:Indoleacetic Acids / Q000378:metabolism*; D007461:Iodoacetates / Q000378:metabolism*; D007700:Kinetics; D009687:Nuclear Proteins / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000378:metabolism*
D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D007461:Iodoacetates; D009687:Nuclear Proteins; D010940:Plant Proteins; D020744:rac GTP-Binding Proteins