Plant wound responses via glutamate and calcium signaling

Abstract

Unlike animals, plants do not possess the central nervous system, but they can immediately sense local environmental stresses, such as mechanical wounding and herbivore attack, propagate this information throughout the plant body and activate systemic defence responses in distant organs.　However, the molecular machinery underlying such rapid sensory and systemic signal transduction is poorly understood.　Using genetically-encoded calcium ion （Ca²⁺） and glutamic acid （Glu） indicators and a highly-sensitive wide-field fluorescence microscope, we have visualized the plant-wide spatial and temporal dynamics of cytosolic Ca²⁺ and apoplastic Glu levels in response to wounding in Arabidopsis leaves.　Here, we show that glutamate is a wound signal in plants that is leaked to the apoplastic region from damaged cells/tissues.　The GLUTAMATE RECEPTOR LIKE （GLR） family of Ca²⁺-permeable channels act as sensors that convert this damage-associated signal into an increase in cytosolic Ca²⁺ concentration.　This Ca²⁺ signal propagates throughout the entire plant via the plant-specific tissue/structure, phloem and plasmodesmata, and preemptively activates resistance responses in the distant undamaged organs.