Aromatic monoamine-induced immediate oxidative burst leading to an increase in cytosolic Ca2+ concentration in tobacco suspension culture.

Aromatic monoamines may contribute to both chemical and physical protection of plants. Addition of phenylethylamine (PEA) and benzylamine to tobacco suspension culture (cell line BY-2) induced a very rapid and transient generation of two active oxygen species (AOS), H2O2 and superoxide anion, both detected with chemiluminescence. Electron spin resonance spectroscopy revealed that hydroxy radicals are also produced. With laser-scanning confocal microscopy, fluorescence spectroscopy and microplate fluorescence reading, intracellular H2O2 production was detected using dichlorofluorescin diacetate as a fluorescent probe. Following AOS production, cytosolic Ca2+ concentration ([Ca2+]c) of the tobacco cells, monitored with luminescence of transgenic aequorin, increased and attained to a peak level 12 s after PEA addition. The PEA-induced increase in [Ca2+]c was inhibited by a Ca2+ chelator, Ca2+ antagonists and AOS scavengers, suggesting that PEA-induced AOS triggered a Ca2+ influx across the plasma membrane.