Ether Anesthetics Obstructs Touch-Induced Trigger Hair Calcium-Electrical Signals Preventing Excitation of The Venus Flytrap

Abstract

Plants do not have neurons. Instead they operate transmembrane ion channels and can be electrically excited by physical and chemical clues. The Venus flytrap with its distinctive hapto-electric signaling is a prime example. When an insect collides with the trigger hairs emerging from the inner surface of the trap, the mechanical stimulus in the mechanosensory organ is translated into a calcium signal and an action potential (AP). Here we asked how a Ca 2+ wave and AP are initiated in the trigger hair and how these are fed into the systemic trap calcium-electric network. When the Dionaea muscipula trigger hair matures and develops hapto-electric excitability, the mechanosensitive anion channel DmMSL10 and voltage dependent SKOR type Shaker K + channel are expressed in the shear stress-sensitive podium, which interfaces with the flytrap’s prey capture and processing networks. In the excitable state, touch stimulation of the trigger hair first evokes a rise in the podium Ca 2+ , then the calcium signal together with an action potential, travel over the entire trap surface. Seeking the mechanisms that mediate touch-induced Ca 2+ transients in the mature trigger hairs, we show that OSCA1.7 and GLR3.6 type Ca 2+ channels and ACA2/10 Ca 2+ pumps are specifically expressed in the podium. In addition, we found that direct glutamate application to the trap evoked a propagating Ca 2+ and electrical event. Given that anesthetics affect K + channels and glutamate receptors in animal systems, we exposed flytraps to ether. An ether atmosphere suppressed the propagation of touch and glutamate-induced Ca 2+ and AP long-distance signaling, a response that was completely recovered when ether was replaced by fresh air. In line with ether targeting a calcium channel, so triggering a Ca 2+ activated anion channel, the AP amplitude declined before the electrical signal ceased completely. Ether in the mechanosensory organ neither prevented the touch induction of a calcium signal nor its post stimulus decay. This finding indicates that ether prevents the touch activated GLR3.6-expressing base of the trigger hair so exciting the capture organ.