Opinion Electrical Wiring and Long-Distance Plant Communication Rainer Hedrich, 1, * Vicenta Salvador-Recatalà, 1 and Ingo Dreyer 2, * Electrical signalling over long distances is an efficient way of achieving cell-to- cell communication in living organisms. In plants, the phloem can be consid- ered as a ‘green cable’ that allows the transmission of action potentials (APs) induced by stimuli such as wounding and cold. Measuring phloem potential changes and separating them from secondary responses of surrounding tis- sues can be achieved using living aphids as bioelectrodes. Two glutamate receptor-like genes (GLR3.3 and 3.6) were identified as being involved in the propagation of electrical activity from the damaged to undamaged leaves. However, phloem APs are initiated and propagated independently of these glutamate receptors. Here, we propose new screening approaches to obtain further information on the components required for electrical signalling in phloem cables. Remote Signalling in Animals and Plants Long-range signalling in higher organisms is essential for flexible responses to environmental threats and challenges. Animals have a nervous system that allows fast transmission of electrical signals between different parts of the body. The sensing of a stimulus, such as heat when accidentally touching an oven, is converted into the contraction of muscles, pulling the wounded hand away. These electrical circuits are based on a dense network of nerve cells connected via their axons. The axons operate as cables that conduct information encoded by the number and frequency of transitory APs. By contrast, higher plants do not have specialised nerve cells with axons, but similar to animals, they do operate long-distance electrical signalling. Indeed, mechanically induced transient electrical AP-like waves in Venus flytrap (Dionaea muscipula) were reported by Darwin [1], long before Cole and Curtis recorded similar signals in squid [2]. Later, Hodgkin and Huxley established the ion channel basis of the AP in the squid giant axon [3]. The patch clamp technique, in combination with advanced molecular cell biology and genomics, has provided a detailed picture of the channels and receptors of the human nervous system. Although similar studies have been conducted in plants, the cellular and molecular nature of the green circuits remain largely unknown. In this opinion, we show that the phloem network conducts long-distance electrical signals and argue that they are carried by voltage-dependent plant-specific ion channels. We propose that screens for mutants in phloem electrical signalling using phloem-expressed genetically encoded voltage-sensing dyes will provide new insights into plant whole-body communication and the underlying membrane receptors and channels operating the green circuit. Trends The phloem of higher plants serves as a cable for long-distance electrical signalling. Aphids can be used as bioelectrodes to study plant electrical communication. Leaf wounding and cold stimuli induce phloem-travelling APs. APs do not require the GLR 3.3/3.6 glutamate receptor pair. 1 Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs-Platz 2, 97082 Würzburg, Germany 2 Centro de Bioinformática y Simulación Molecular (CBSM), Universidad de Talca, 2 Norte 685, Talca, Chile *Correspondence: hedrich@botanik.uni-wuerzburg.de (R. Hedrich) and idreyer@utalca.cl (I. Dreyer). TRPLSC 1401 No. of Pages 12 Trends in Plant Science, Month Year, Vol. xx, No. yy http://dx.doi.org/10.1016/j.tplants.2016.01.016 1 © 2016 Elsevier Ltd. All rights reserved.