Abstract
E3 ubiquitin ligases mediate the last step of the ubiquitination pathway in the ubiquitin-proteasome system (UPS). By targeting transcriptional regulators for their turnover, E3s play a crucial role in every aspect of plant biology. In plants, SKP1/CULLIN1/F-BOX PROTEIN (SCF)-type E3 ubiquitin ligases are essential for the perception and signaling of several key hormones including auxins and jasmonates (JAs). F-box proteins, TRANSPORT INHIBITOR RESPONSE 1 (TIR1) and CORONATINE INSENSITIVE 1 (COI1), bind directly transcriptional repressors AUXIN/INDOLE-3-ACETIC ACID (AUX/IAA) and JASMONATE ZIM-DOMAIN (JAZ) in auxin- and JAs-depending manner, respectively, which permits the perception of the hormones and transcriptional activation of signaling pathways. Redox modification of proteins mainly by S-nitrosation of cysteines (Cys) residues via nitric oxide (NO) has emerged as a valued regulatory mechanism in physiological processes requiring its rapid and versatile integration. Previously, we demonstrated that TIR1 and Arabidopsis thaliana SKP1 (ASK1) are targets of S-nitrosation, and these NO-dependent posttranslational modifications enhance protein-protein interactions and positively regulate SCFTIR1 complex assembly and expression of auxin response genes. In this work, we confirmed S-nitrosation of Cys140 in TIR1, which was associated in planta to auxin-dependent developmental and stress-associated responses. In addition, we provide evidence on the modulation of the SCFCOI1 complex by different S-nitrosation events. We demonstrated that S-nitrosation of ASK1 Cys118 enhanced ASK1-COI1 protein-protein interaction. Overexpression of non-nitrosable ask1 mutant protein impaired the activation of JA-responsive genes mediated by SCFCOI1 illustrating the functional relevance of this redox-mediated regulation in planta. In silico analysis positions COI1 as a promising S-nitrosation target, and demonstrated that plants treated with methyl JA (MeJA) or S-nitrosocysteine (NO-Cys, S-nitrosation agent) develop shared responses at a genome-wide level. The regulation of SCF components involved in hormonal perception by S-nitrosation may represent a key strategy to determine the precise time and site-dependent activation of each hormonal signaling pathway and highlights NO as a pivotal molecular player in these scenarios.
Highlights
In eukaryotic organisms, the ubiquitin-proteasome system (UPS) participates in the selective degradation of proteins modulating, in turn, a wide variety of physiological processes (Hershko and Ciechanover, 1998)
We have previously demonstrated that TRANSPORT INHIBITOR RESPONSE 1 (TIR1) and ASK1 subunits of the SCFTIR1 E3 ubiquitin ligase complex are targeted by redox posttranslational modifications (Terrile et al, 2012; Iglesias et al, 2018)
We explore if S-nitrosation of TIR1 in Cys140 is implicated in other auxin-related phenotypes
Summary
The ubiquitin-proteasome system (UPS) participates in the selective degradation of proteins modulating, in turn, a wide variety of physiological processes (Hershko and Ciechanover, 1998). The UPS is central to hormonal regulation in plants since protein ubiquitination and proteasome degradation serve for the orchestration of hormone homeostasis, transport, and perception (Kelley and Estelle, 2012; Dharmasiri et al, 2013). The activation of auxin and jasmonates (JAs) signaling pathways involves the degradation of transcriptional repressors through the action of SCF E3 ubiquitin ligases. Upon hormone binding by SCFTIR1/AFBs-AUX/IAA and SCFCOI1-JAZs co-receptor complexes, poly-ubiquitination and degradation of AUX/IAA and JAZ transcriptional repressors take place. This consecutively promotes shuffling of the transcriptional machinery promoting auxin- and JAs-responsive genes activation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
