| 15994909 |
Tao LZ, Cheung AY, Nibau C, Wu HM: RAC GTPases in tobacco and Arabidopsis mediate auxin-induced formation of proteolytically active nuclear protein bodies that contain AUX/IAA proteins. Plant Cell. 2005 Aug;17(8):2369-83. Epub 2005 Jul 1.
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. |
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