Arabidopsis PROTEASOME REGULATOR1 is required for auxin-mediated suppression of proteasome activity and regulates auxin signalling

By Bao-Jun Yang, Xinxin Han, L. Yin, M. Xing, Zhi-hong Xu, Hong-Wei Xue. Nature Communications, 2016

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The plant hormone auxin is perceived by the nuclear F-box protein TIR1 receptor family and regulates gene expression through degradation of Aux/IAA transcriptional repressors. Several studies have revealed the importance of the proteasome in auxin signalling, but details on how the proteolytic machinery is regulated and how this relates to degradation of Aux/IAA proteins remains unclear. Here we show that an Arabidopsis homologue of the proteasome inhibitor PI31, which we name PROTEASOME REGULATOR1 (PTRE1), is a positive regulator of the 26S proteasome. Loss-of-function ptre1 mutants are insensitive to auxin-mediated suppression of proteasome activity, show diminished auxin-induced degradation of Aux/IAA proteins and display auxin-related phenotypes. We found that auxin alters the subcellular localization of PTRE1, suggesting this may be part of the mechanism by which it reduces proteasome activity. Based on these results, we propose that auxin regulates proteasome activity via PTRE1 to fine-tune the homoeostasis of Aux/IAA repressor proteins thus modifying auxin activity. Plant responses to auxin require proteasome-mediated degradation of Aux/IAA transcriptional repressor proteins. Here, Yang et al. show that auxin suppresses proteasome activity in a manner dependent on the proteasome regulator PTRE1 and propose a mechanism for fine tuning Aux/IAA homoeostasis.

Subfields: Molecular Biology, Plant Science

View Paper: https://www.semanticscholar.org/paper/d7eff7b84ef4e28d5784ce7b72397e264a8eec22