EPR EVIDENCE FOR GENERATION OF HYDROXYL RADICAL TRIGGERED BY N-ACETYLCHITOOLIGOSACCHARIDE ELICITOR AND A PROTEIN PHOSPHATASE INHIBITOR IN SUSPENSION-CULTURED RICE CELLS
K. Kuchitsu et al., EPR EVIDENCE FOR GENERATION OF HYDROXYL RADICAL TRIGGERED BY N-ACETYLCHITOOLIGOSACCHARIDE ELICITOR AND A PROTEIN PHOSPHATASE INHIBITOR IN SUSPENSION-CULTURED RICE CELLS, Protoplasma, 188(1-2), 1995, pp. 138-142
N-acetylchitooligosaccharides, fragments of the backbone of fungal cel
l wall, trigger rapid membrane responses such as transient depolarizat
ion, and elicit defense reactions including phytoalexin production in
suspension-cultured rice cells. The generation of reactive oxygen spec
ies triggered by the oligosaccharide signal was analyzed with EPR spec
troscopy using a spin trapping system, 4-pyridyl 1-oxide N-tert-butyl
nitrone (4-POBN) and ethanol.(OH)-O-. generation was detected as the a
lpha-hydroxyethyl adduct of 4-POBN after elicitation. Superoxide dismu
tase, catalase or diethylenetriamine pentaacetic acid, a metal chelato
r, inhibited O-. generation, proposing the following reaction sequence
: generation of O-.(2)- in response to the oligosaccharide elicitor, f
ollowed by dismutation to H2O2, then generation of (OH)-O-. by the rea
ction of H2O2 with Fe2+ that is generated by the reduction of Fe3+ by
O-.(2)-. Generation of the same reactive oxygen species was also trigg
ered by calyculin A, a protein phosphatase inhibitor, alone, suggestin
g the involvement of protein phosphorylation in its regulation during
the oligosaccharide signal transduction.