Auxin-dependent post-translational regulation of MONOPTEROS in the Arabidopsis root

• Published in: Cell reports (Cambridge) 2024-12, Vol.43 (12), p.115083, Article 115083
• Main Authors: Cavalleri, Alex, Astori, Chiara, Truskina, Jekaterina, Cucinotta, Mara, Farcot, Etienne, Chrysanthou, Elina, Xu, Xiaocai, Muino, Jose M., Kaufmann, Kerstin, Kater, Martin M., Vernoux, Teva, Weijers, Dolf, Bennett, Malcolm J., Bhosale, Rahul, Bishopp, Anthony, Colombo, Lucia
• Format: Article
• Language: English
• Subjects: Arabidopsis; ARFs post-translational regulation; auxin; auxin response factor; auxin signalling; CP: Plants; MONOPTEROS; root development
• ISSN: 2211-1247; 2211-1247
• DOI: 10.1016/j.celrep.2024.115083

Auxin plays a pivotal role in plant development by activating AUXIN RESPONSE FACTORs (ARFs). Under low auxin levels, ARF activity is inhibited by interacting with Aux/IAAs. Aux/IAAs are degraded when the cellular auxin concentration increases, causing the release of ARF inhibition. Here, we show that levels of the ARF5/MONOPTEROS (MP) protein are regulated in a cell-type-specific and isoform-dependent manner. We find that the stability of MP isoforms is differentially controlled depending on the auxin level. The canonical MP isoform is degraded by the proteasome in root tissues with low auxin levels. While auxin sharpens the MP localization domain in roots, it does not do so in ovules or embryos. Our research highlights a mechanism for providing spatial control of auxin signaling capacity. Together with recent advances in understanding the tissue-specific expression and post-transcriptional modification of auxin signaling components, these results provide insights into understanding how auxin can elicit so many distinct responses. [Display omitted] •In roots, full-length MP and MP11ir isoform accumulation is post-translationally regulated•Full-length MP protein is stable in tissues with high auxin•At low auxin levels, full-length MP interactions with AUX/IAAs determine its degradation•MP isoform regulation is required to control root development and sensitivity to auxin Cavalleri et al. show that in Arabidopsis roots, the accumulation of MP and MP11ir splicing isoform is post-translationally regulated. MP is stable in high-auxin tissues, whereas interaction with AUX/IAAs causes its degradation at low auxin levels. MP isoforms are required to ensure correct root development and sensitivity to auxin.