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 s uspension culture (cell line BY-2) induced a very rapid and transient gener ation of two active oxygen species (AOS), H2O2 and superoxide anion, both d etected with chemiluminescence. Electron spin resonance spectroscopy reveal ed that hydroxy radicals are also produced. With laser-scanning confocal mi croscopy, fluorescence spectroscopy and microplate fluorescence reading, in tracellular H2O2 production was detected using dichlorofluorescin diacetate as a fluorescent probe. Following AOS production, cytosolic Ca2+ concentra tion ([Ca2+](c)) of the tobacco cells, monitored with luminescence of trans genic aequorin, increased and attained to a peak level 12 s after PEA addit ion. The PEA-induced increase in [Ca2+](c) was inhibited by a Ca2+ chelator , Ca2+ antagonists and AOS scavengers, suggesting that PEA-induced AOS trig gered a Ca2+ influx across the plasma membrane.