The Effect of Neurotransmitters on Programmed Cell Death and Formation of Reactive Oxygen Species in the Pea Leaf Epidermis

Abstract

Neurotransmitters are found not only in animals, but also in other living organisms, including plants. However, the data on the functions of these compounds in the plant world are far from being comprehensive. In particular, the issue concerning their impact on plant cell death still demands further research. In the present study, we tested the effects of neurotransmitters on programmed cell death and the formation of reactive oxygen species (ROS) in plants. Programmed cell death was estimated from the destruction of cell nuclei. ROS was determined using 2′,7′-dichlorofluorescein. Dopamine, norepinephrine, serotonin, histamine, acetylcholine and acetylthiocholine (its synthetic analog) were used. The catecholamines dopamine and norepinephrine suppressed KCN-induced destruction of guard cell nuclei in the pea leaf epidermis at concentrations of 0.01–1 mM. In contrast, serotonin and acetylcholine (1–3 mM) promoted the destruction of nuclei that was induced by KCN. Histamine and acetylthiocholine had no effect on KCN-induced destruction of nuclei at concentrations of 0.01–3 mM. Unlike natural neurotransmitters, acetylthiocholine (3 mM), caused the destruction of guard cell nuclei even when KCN was absent. Dopamine, norepinephrine, and serotonin reduced menadione-induced ROS formation in the pea leaf epidermis. No similar effect was observed with histamine, acetylcholine, and acetylthiocholine. Therefore, dopamine, norepinephrine, and serotonin possess antioxidant properties in plants. In addition, dopamine and norepinephrine prevent cell death.