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.
Tao
Li-Zhen
LZ
Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003, USA.
Cheung
Alice Y
AY
Nibau
Candida
C
Wu
Hen-Ming
HM
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