| dc.description.abstract | The jasmonate family of phytohormones plays central roles in plant development and stress
acclimation. However, the architecture of their signaling circuits remains largely unknown. Here,
we describe the versatile activity of jasmonate family binding protein, cyclophilin 20-3 (CYP20-
3), positioned as a key regulator in controlling the interface between 12-oxo-phytodienoic acid
(OPDA, defense) and light-dependent redox (growth) signaling. The latter, also known as the
electron (e¯) transport chain (ETC) photosystem I (PSI), is a primary metabolism converting solar
energy into biologically useful chemical energies, necessary for the production of overall biomass
of plants and living organisms. When the PSI captures solar energy, it excites e¯ that reduce
thioredoxins (TRXs) via a ferredoxin (Fd) and a Fd-TRX reductase (FTR). TRXs, small
oxidoreductases, then deliver e¯ and activate target enzymes in the Calvin cycle that balances
consumption in photosynthesis. The present study validated that TRXs can also reduce other
Calvin cycle-unrelated proteins including CYP20-3 and photosynthetic ETC as an e¯ donor of 2-
cysteine (Cys) peroxiredoxin A (2CPA). Plastid 2CPA is a thiol-based peroxidase involved in
protecting and optimizing photosynthesis. When arrived at the chloroplasts, 2CPA is activated by
oxidation folding with GSH (also called, S-glutathionylation), which in turn reduces toxic
byproducts (e.g., H2O2) in photosynthesis or activates Calvin cycle enzymes such as a fructose
1,6-bisphosphatase. In line with this scenario, OPDA-binding promotes the interaction of CYP20-
3 with TRXs (esp., type-f2), illuminating the mode of OPDA/CYP20-3 signaling in transferring
e¯ from TRX-f2 to SAT1. This then stimulates plastid sulfur assimilations and subsequently GSH
accumulations, which coordinates redox-resolved nucleus gene expressions in defense responses
against biotic and abiotic stresses, while accelerating the S-glutathionylation (activation) of 2CPA
that promotes photosynthetic energy productions, postulating that OPDA/CYP20-3 signaling
optimizes growth, reproduction and survival of plants under constant environmental stresses.
Traditionally, the cost of resistance (often referred to as growth and defense tradeoff) has been
typically described as a teeter-totter model where for defense to increase, growth must decrease
3
and vice versa. This model well circumstantiates the responses of plants to the persistent and excess
surge of environmental stresses. However, in nature, plants are more often situated to encounter a
consistent array of temporal and modest levels of environmental changes, while concurrently
trying to ensure normal growth and developmental processes, in order to maximize their yields
and production. Hence, recent studies have begun to elaborate an alternative model, “growth and
defense coordination”, wherein a balancing act between growth and defense can synergistically
optimize plant fitness. In agreement, plant acclimations towards environmental changes and
pressures causing oxidative stresses (e.g., tissue injury, excess light and temperature, and drought
and salinity) accompany the accumulation of OPDA on a time sale of hours with concomitant
accumulation of reduced, nonprotein thiols. | en_US |
