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.
THE PLANT CELL 2005;
17:2369-83. [PMID:
15994909 PMCID:
PMC1182495 DOI:
10.1105/tpc.105.032987]
[Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
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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