Plant Stress Signaling in a Cross-Kingdom Context: Metabolic Control of Redox and ROS-Ca2+-Hormone Interactomes.

Biological systems maintain functional integrity under environmental stress through tightly coordinated signaling networks, yet the mechanisms that preserve signal fidelity in the presence of stochastic oxidative and ionic fluctuations across taxa remain incompletely understood. Although redox regulation, coupling between reactive oxygen species (ROS) and Ca2+, and hormone-mediated feedback loops have been extensively characterized within individual kingdoms, a cross-kingdom framework linking these pathways through metabolite-mediated modulation is lacking. Here, a cross-kingdom compilation of evidence from plant, animal, and microbial systems is presented to examine how specific endogenous and microbe-derived metabolites and plant fructans modulate the fidelity of stress signaling networks. We propose a metabolite-guided signal fidelity hypothesis in which certain specialized metabolites act as molecular stabilizers in the response of organisms to stress. They buffer transient ROS bursts, limit variability in calcium signaling, and strengthen hormone-regulated feedback loops. Together, these functions preserve the signal-to-noise ratio of stress responses, independent of overt toxicity. These insights lay the groundwork for testable predictions and the development of translational strategies in agriculture, biotechnology, and medicine aimed at improving stress tolerance by stabilizing the flow of biological information.