Professor Stanisław Karpiński’s team described and explained the new mechanism of plant-to-plant direct communication.
Professor Stanisław Karpiński’s team described and explained the new mechanism of plant-to-plant direct communication.
Plants can warn each other about the danger. They communicate with each other using a new type of plant-to-plant direct communication involving electrical signaling.
A team of scientists led by prof. Stanisław Karpiński from the Institute of Biology, SGGW, together with the scientists from the University of Missouri (USA), described the quantum-molecular and physiological systems of an unknown form of direct communication between plants, and its mechanism named Network Acquired Acclimation, NAA). The results were presented in The Plant Cell, the most prestigious journal publishing articles on plant cell biology. An injured leaf (e.g., by insect herbivory or excess light) generates electrical signals (ES) that spread to tissues, leaves, and organs of the entire plant. ES are mediated by changes in the activity of ion channels and are accompanied by waves of reactive oxygen species (ROS) and non photochemical quenching (NPQ). These waves are interdependent and propagate systematically throughout the plant. This process is essential for priming specific changes in gene expression and plant acclimation (e.g., cellular light memory). As a result, the entire plant enters a state of Systemic Acquired Acclimation (SAA). Under humid conditions, an injured plant can directly communicate a danger signal to other plants that touch it within a community of plants, like a meadow of dandelions.
ES and ROS waves serve as plant-to-plant signals propagating on and in the leaf with a velocity of several mm per s or cm per min, respectively. These signals can induce changes in NPQ, chloroplast retrograde signaling, gene expression, phytohormones, ROS signaling, and acclimation responses, in neighboring plants. Most of these complex communication responses can also be induced between two plants connected by a copper wire circuit, indicating that ES is the main player of plant-to-plant communication.
Professor Karpinski’s team found that ES and ROS induce a new acclimation phenomenon termed “Network Acquired Acclimation (NAA)” necessary for SAA induction within a plant community.
The mechanisms by which plants can transmit chemical signals to each other were known before, e.g. when African acacia leaves are eaten by giraffes, volatile chemical compounds (e.g. jasmonic acid) begin to synthesize. This is a signal for neighboring plants and leaves to produce bitter alkaloids, substances that alter the taste and therefore make them less attractive as food. It was also known that, for example, the roots of neighboring plants communicate to their neighbors’ signals about the availability of water and minerals through soil fungus hyphae.
Our research confirms that surface electrical signals function as a communication link between plants, which are organized as a global network (community) of plants – as James Cameron portrayed in the movie Avatar. So they act a bit like Facebook or Twitter, says Professor Karpiński
A model that summarizes the Network Acquired Acclimation (NAA) responses in two different plants. Plants that live as a community, like dandelion (Taraxacum officinale) or Arabidopsis (Arabidopsis thaliana), can use canopy-wide ES to communicate with each other and induce systemic acquired acclimation (SAA) within one plant and NAA between plants. Leaves belonging to two different plants (transmitter and receiver) must be connected by a simple touch and electrical conductivity is required (e.g. high relative humidity, represented by a drop of water). The direct aboveground ES transmission between a stressed transmitter plant and an unstressed receiver plant is driving spatial changes in the distribution of photosynthetic energy and induction of common signaling and defense molecules in the receiver plant, and this type of plant-to-plant aboveground communication can occur in a community of plants to induce network acquired acclimation (NAA). ES has a modulated amplitude (interdependent ion fluxes) and drives spatiotemporal changes in energy quenching (NPQ), the subsequent induction of the reactive oxygen species (ROS) wave, and retrograde signaling (RS) in both transmitter and receiver plants. ROS wave propagation depends on the specific regulation by RBOHD, superoxide dismutase (SOD), and catalase (CAT) activities. Additionally, GRLs and MSL10 are implicated in alterations of ROS, Ca2 +, and ES waves. The autopropagation of ROS can occur in the receiver cells. ES, the ROS wave, and RS induce gene expression changes in both in transmitter and receiver plants, such as for example ZAT12 and APX2, markers of systemic signaling.
Red lines, ES-dependent signaling; blue lines, ROS-dependent signaling; green lines, NPQ-dependent signaling; red dashed line, hypothetical ES induced by current provided through a metal wire.