Mobile Signalling in Plants under Abiotic Stress: Insight from Root Shoot Communication

A cordial communication between the root and shoot occurs for proper absorption of water and essential nutrients, which leads to plant growth and development. This communication is often disrupted when plants face an environmental stress such as water deficit, soil salinity, high/low temperature or shade, etc. This communication is maintained through various signals, including hormones, peptides, proteins, hydraulic signals, and metabolites, which are transported primarily through the vasculature (root) to distant tissues (above-ground plant parts). Root-localized stress signals trigger changes in xylem hydraulics, mobile peptides, reactive oxygen species (ROS), and Ca2+, which lead to remote effects and induce stomatal closure. The mobility of HY5 protein and its downstream targets via the phloem conveys shoot-sensed light and temperature information to affect both primary and lateral root growth. Shoot-derived sucrose loading/unloading in the phloem is highly responsive to environmental changes, and triggers signalling pathways that regulate root development. Developmental plasticity of the vasculature in response to abiotic stresses is of key importance for long-distance transport of substances to assist plant stress resilience. How shoots and roots synchronize their response to environmental stress using mobile signals is an emerging field of research. We summarize recent studies on mobile signals regulating shoot stomatal movement and root development in response to specific environmental stresses.