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Summary The plant hormone abscisic acid (ABA) plays crucial roles in regulation of stress responses and growth modulation. Heterotrimeric G‐proteins are key mediators of ABA responses. Both ABA and G‐proteins have also been implicated in intracellular redox regulation; however, the extent to which reversible protein oxidation manipulates ABA and/or G‐protein signaling remains uncharacterized.To probe the role of reversible protein oxidation in plant stress response and its dependence on G‐proteins, we determined the ABA‐dependent reversible redoxome of wild‐type and Gβ‐protein null mutantagb1of Arabidopsis.We quantified 6891 uniquely oxidized cysteine‐containing peptides, 923 of which show significant changes in oxidation following ABA treatment. The majority of these changes required the presence of G‐proteins. Divergent pathways including primary metabolism, reactive oxygen species response, translation and photosynthesis exhibited both ABA‐ and G‐protein‐dependent redox changes, many of which occurred on proteins not previously linked to them.We report the most comprehensive ABA‐dependent plant redoxome and uncover a complex network of reversible oxidations that allow ABA and G‐proteins to rapidly adjust cellular signaling to adapt to changing environments. Physiological validation of a subset of these observations suggests that functional G‐proteins are required to maintain intracellular redox homeostasis and fully execute plant stress responses.
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Profiling thimet oligopeptidase‐mediated proteolysis in Arabidopsis thaliana
SUMMARY Protein homeostasis (proteostasis) is crucial for proper cellular function, including the production of peptides with biological functions through controlled proteolysis. Proteostasis has roles in maintenance of cellular functions and plant interactions with the environment under physiological conditions. Plant stress continues to reduce agricultural yields causing substantial economic losses; thus, it is critical to understand how plants perceive stress signals to elicit responses for survival. As previously shown inArabidopsis thaliana, thimet oligopeptidases (TOPs) TOP1 (also referred to as organellar oligopeptidase) and TOP2 (also referred to as cytosolic oligopeptidase) are essential components in plant response to pathogens, but further characterization of TOPs and their peptide substrates is required to understand their contributions to stress perception and defense signaling. Herein, label‐free peptidomics via liquid chromatography‐tandem mass spectrometry was used to differentially quantify 1111 peptides, originating from 369 proteins, between the Arabidopsis Col‐0 wild type andtop1top2knock‐out mutant. This revealed 350 peptides as significantly more abundant in the mutant, representing accumulation of these potential TOP substrates. Ten direct substrates were validated usingin vitroenzyme assays with recombinant TOPs and synthetic candidate peptides. These TOP substrates are derived from proteins involved in photosynthesis, glycolysis, protein folding, biogenesis, and antioxidant defense, implicating TOP involvement in processes aside from defense signaling. Sequence motif analysis revealed TOP cleavage preference for non‐polar residues in the positions surrounding the cleavage site. Identification of these substrates provides a framework for TOP signaling networks, through which the interplay between proteolytic pathways and defense signaling can be further characterized.
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- PAR ID:
- 10452500
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- The Plant Journal
- Volume:
- 106
- Issue:
- 2
- ISSN:
- 0960-7412
- Page Range / eLocation ID:
- p. 336-350
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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