A tidal wave of signals: calcium and ROS at the forefront of rapid systemic signaling

• Rapid systemic signaling is essential for plant acclimation to abiotic stresses.
• Waves of Ca2+ and ROS mediate systemic cell-to-cell communication in plants.
• Electric signals may facilitate the rate of the Ca2+ and ROS wave pathway.
• A model for the integration of the Ca2+ and ROS waves is presented.

Systemic signaling pathways enable multicellular organisms to prepare all of their tissues and cells to an upcoming challenge that may initially only be sensed by a few local cells. They are activated in plants in response to different stimuli including mechanical injury, pathogen infection, and abiotic stresses. Key to the mobilization of systemic signals in higher plants are cell-to-cell communication events that have thus far been mostly unstudied. The recent identification of systemically propagating calcium (Ca2+) and reactive oxygen species (ROS) waves in plants has unraveled a new and exciting cell-to-cell communication pathway that, together with electric signals, could provide a working model demonstrating how plant cells transmit long-distance signals via cell-to-cell communication mechanisms. Here, we summarize recent findings on the ROS and Ca2+ waves and outline a possible model for their integration.