A redox-driven phase switch: RCD1 condensates decode growth and stress adaptation.

Area of Science:

• Plant biology
• Molecular signaling
• Biochemistry

Background:

• Plants must differentiate between physiological reactive oxygen species (ROS) and stress-induced ROS for proper growth and acclimation.
• The "specificity paradox" in ROS signaling highlights the challenge plants face in interpreting these signals.

Purpose of the Study:

• To elucidate the mechanism by which plants discriminate between physiological and stress-derived ROS signals.
• To identify key molecular players involved in redox sensing and signaling in plants.

Main Methods:

• Investigated the role of Radical-induced Cell Death1 (RCD1) in ROS signal specificity.
• Utilized studies on liquid-liquid phase separation (LLPS) to understand RCD1's function.
• Examined the impact of ROS accumulation on RCD1 structure and function.
• Analyzed the role of transcription factor ASYMMETRIC LEAVES1 (AS1) and ZAT12 in RCD1-mediated signaling.

Main Results:

• Identified RCD1 as a redox-responsive molecular sieve crucial for ROS signal discrimination.
• Demonstrated that RCD1 undergoes liquid-liquid phase separation (LLPS) under basal conditions, forming nuclear condensates that sequester AS1.
• Showed that stress-induced ROS trigger oxidation of RCD1's cysteine triad, leading to phase separation and release of AS1.
• Revealed that this structural reorganization activates ZAT12-mediated antioxidant defenses.

Conclusions:

• Redox-driven phase separation of RCD1 is a key regulatory mechanism for plant acclimation.
• RCD1 acts as a molecular sieve, controlling the spatiotemporal recalibration of plant physiological states in response to ROS.
• This mechanism allows plants to rapidly adjust their responses to varying ROS levels, distinguishing between growth signals and environmental stress.