Nitric Oxide and Redox Signaling Networks Governing Plant Stem Cell Homeostasis

Sustained plant growth depends on stem cell populations in the shoot and root apical meristems (SAM and RAM), where coordinated regulation of self-renewal, proliferation, quiescence, and differentiation support continuous organ formation. Nitric oxide (NO) and reactive oxygen species (ROS) constitute an interconnected redox signaling system that links metabolism and environmental perception with stem cell regulation. Their spatial and temporal dynamics establish distinct redox environments within meristems, contributing to the organization of proliferative and differentiation domains. In RAM, superoxide and hydrogen peroxide show contrasting spatial patterns, whereas redox regulation in SAM is integrated with stem cell maintenance and developmental transitions. NO further influences stem cell behavior through transcriptional regulation, S-nitrosylation and other redox-dependent post-translational modifications, and interactions with antioxidant and redox-buffering systems. These mechanisms intersect with key regulators including PLT, WUS, UPB1, and transcriptional networks, linking redox status with cell-cycle progression and stem cell fate. Crosstalk with auxin, cytokinin, gibberellin, abscisic acid, and other hormonal pathways integrate NO-ROS signaling with developmental programs. Mitochondrial function, energy status, nutrient availability, and TOR-associated growth regulation further shape the redox environment of meristematic cells. Environmental conditions, including hypoxia, nutrient limitation, salinity, and heavy-metal stress, remodel NO-ROS dynamics and thereby influence meristem activity and stress adaptation. Redox regulation also intersects with epigenetic processes such as DNA methylation, connecting transient signals with longer-term developmental responses. These relationships reveal NO-ROS signaling as a central interface between redox homeostasis, developmental regulation, and environmental adaptation, with potential implications for maintaining meristem resilience, regenerative capacity, and crop performance.