Abstract
In plants, growth-defense trade-offs occur because of limited resources, which demand prioritization towards either of them depending on various external and internal factors. However, very little is known about molecular mechanisms underlying their occurrence. Here, we describe that cyclophilin 20-3 (CYP20-3), a 12-oxo-phytodienoic acid (OPDA)-binding protein, crisscrosses stress responses with light-dependent electron reactions, which fine-tunes activities of key enzymes in plastid sulfur assimilations and photosynthesis. Under stressed states, OPDA, accumulates in the chloroplasts, binds and stimulates CYP20-3 to convey electrons towards serine acetyltransferase 1 (SAT1) and 2-Cys peroxiredoxin A (2CPA). The latter is a thiol-based peroxidase, protecting and optimizing photosynthesis by reducing its toxic byproducts (e.g., H2O2). Reduction of 2CPA then inactivates its peroxidase activity, suppressing the peroxide detoxification machinery, whereas the activation of SAT1 promotes thiol synthesis and builds up reduction capacity, which in turn triggers the retrograde regulation of defense gene expressions against abiotic stress. Thus, we conclude that CYP20-3 is a unique metabolic hub conveying resource allocations between plant growth and defense responses (trade-offs), ultimately balancing optimal growth phonotype.
Highlights
Peroxiredoxins (PRXs) are ubiquitous and the most abundant thiolbased peroxidases capable of reducing a broad range of toxic peroxides in the presence of sufficient electron (H+, e−) donors
The present study demonstrates that heat stress (HS) prompts cyclophilin 20-3 (CYP20-3) to temporally limit an antioxidant machinery of GSHglutathionylated 2-Cys peroxiredoxin A (2CPA) (2CPAGS) in photosynthesis, while relaying an oxo-phytodienoic acid (OPDA) signal, which triggers the retrograde regulation of nucleus defense gene (e.g., HSP17.6, HSP70, and CYP18D11) expressions
Our preparatory analyses uncovered that 2CPs, prepared recombinantly in Escherichia coli, uniquely bind a negatively charged tripeptide GSH, a major nonprotein thiol antioxidant in plants (Fig S1)
Summary
Peroxiredoxins (PRXs) are ubiquitous and the most abundant thiolbased peroxidases capable of reducing a broad range of toxic peroxides in the presence of sufficient electron (H+, e−) donors. These data highlight a novel activity of GSH as a functional group of posttranslational modifiers, apart from its antioxidant activity, which determine (i) the quaternary structure and (ii) the cellular activity of enzymes (e.g., 2CPGS isoforms), and (iii) directed their metabolic pathways (i.e., reductant signaling), controlling the interface between plant growth, defense responses, and stress acclimation processes.
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