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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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Protein interactome of 3′,5′‐cAMP reveals its role in regulating the actin cytoskeleton
SUMMARY Identification of protein interactors is ideally suited for the functional characterization of small molecules. 3′,5′‐cAMP is an evolutionary ancient signaling metabolite largely uncharacterized in plants. To tap into the physiological roles of 3′,5′‐cAMP, we used a chemo‐proteomics approach, thermal proteome profiling (TPP), for the unbiased identification of 3′,5′‐cAMP protein targets. TPP measures shifts in the protein thermal stability upon ligand binding. Comprehensive proteomics analysis yielded a list of 51 proteins significantly altered in their thermal stability upon incubation with 3′,5′‐cAMP. The list contained metabolic enzymes, ribosomal subunits, translation initiation factors, and proteins associated with the regulation of plant growth such as CELL DIVISION CYCLE 48. To functionally validate obtained results, we focused on the role of 3′,5′‐cAMP in regulating the actin cytoskeleton suggested by the presence of actin among the 51 identified proteins. 3′,5′‐cAMP supplementation affected actin organization by inducing actin‐bundling. Consistent with these results, the increase in 3′,5′‐cAMP levels, obtained either by feeding or by chemical modulation of 3′,5′‐cAMP metabolism, was sufficient to partially rescue the short hypocotyl phenotype of theactin2 actin7mutant, severely compromised in actin level. The observed rescue was specific to 3′,5′‐cAMP, as demonstrated using a positional isomer 2′,3′‐cAMP, and true for the nanomolar 3′,5′‐cAMP concentrations reported for plant cells.In vitrocharacterization of the 3′,5′‐cAMP–actin pairing argues against a direct interaction between actin and 3′,5′‐cAMP. Alternative mechanisms by which 3′,5′‐cAMP would affect actin dynamics, such as by interfering with calcium signaling, are discussed. In summary, our work provides a specific resource, 3′,5′‐cAMP interactome, as well as functional insight into 3′,5′‐cAMP‐mediated regulation in plants.
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- Award ID(s):
- 2226270
- PAR ID:
- 10447947
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- The Plant Journal
- Volume:
- 115
- Issue:
- 5
- ISSN:
- 0960-7412
- Page Range / eLocation ID:
- p. 1214-1230
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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