ROS are universal cell-to-cell stress signals.

The interplay between reactive oxygen species (ROS) and the redox state of cells is deeply rooted in the biology of almost all organisms, regulating development, growth, and responses to the environment. Recent studies revealed that the ROS levels and redox state of one cell can be transmitted, as an information 'state' or 'currency', to other cells and spread by cell-to-cell communication within an entire community of cells or an organism. Here, we discuss the different pathways that mediate cell-to-cell signaling in plants, their hierarchy, and the different mechanisms that transmit ROS/redox signaling between different cells. We further hypothesize that ROS/redox signaling between different organisms could play a key role within the 'one world' principle, impacting human health and our future. [Display omitted] • The interplay between ROS and redox is deeply rooted in the biology of many different organisms. • The ROS/redox state of one cell can be transmitted to other cells generating a chain of cell-to-cell signaling events. • ROS/redox signaling is linked with other signal transduction pathways in cells controlling systemic signaling/acclimation. • Cell-to-cell transfer of ROS/redox states between different organisms links environmental stress to human health. • Hydrogen peroxide is a universal cell-to-cell signal and possibly one of the first stress hormones to emerge on Earth. [ABSTRACT FROM AUTHOR]