Wound-induced Rapid Systemic Calcium Signaling in Arabidopsis

Plants, unlike animals, do not have a nervous system, but they can rapidly perceive local environmental stresses (i.e., mechanical wounding and herbivore attack), propagate this information throughout the plant body and activate systemic responses. However, the molecular basis underlying such rapid sensory and systemic signal transduction remains unclear. Using genetically-encoded Ca2+ and glutamic acid (Glu) indicators, we have visualized the plant-wide spatial and temporal dynamics of cytosolic Ca2+ and apoplastic Glu in response to wounding stress in Arabidopsis. Mechanical wounding caused immediate Ca2+ and Glu increases in the wounded leaf and subsequently this Ca2+ increase was transmitted via the phloem to distant target leaves. In these target leaves, defense marker genes and jasmonic acid/jasmonoyl-isoleucine were highly up-regulated within 2 minutes of mechanical wounding. We also found that the GLUTAMETE RECEPTOR LIKE (GLR) family of Ca2+-permeable channels was required for the wound-induced Ca2+ transmission and extracellularly-applied Glu in a leaf could trigger the similar systemic Ca2+ transmission and resistance responses. These data suggest that the plant GLR is a sensor to monitor the apoplastic Glu levels, and when symplastic Glu is leaked out of wounded cells GLR rapidly creates the Ca2+ signal propagating throughout the entire plant and activates systemic resistance responses in distant organs.