Nitric oxide (NO) as an intermediate in the cryptogein-induced hypersensitive response--a critical re-evaluation.
A hypersensitive response (HR) was induced in tobacco leaves and cell suspensions by the fungal elicitor cryptogein, and NO production was followed by chemiluminescence and occasionally by diaminofluorescein (DAF)-fluorescence. Results from both methods were at least partly consistent, but kinetics was different. NO emission was not induced by cryptogein in leaves, whereas in cell suspensions some weak NO emission was observed, which was nitrate reductase (NR)-dependent, but not required for cell death. Nitric oxide synthase (NOS) inhibitors did not prevent cell death, but PR-1 expression was weakened. In conclusion, neither NR nor NOS appear obligatory for the cryptogein-induced HR. However, a role for NO was still suggested by the fact that the NO scavenger cPTIO prevented the HR. Unexpectedly, cPTI, the reaction product of cPTIO and NO, also impaired the HR but without scavenging NO. Thus, prevention of the HR by cPTIO is not necessarily indicative for a role of NO. Further, even a 100-fold NO overproduction (over wild type) by a nitrite reductase-deficient mutant did not interfere with the cryptogein-induced HR. Accordingly, the role of NO in the HR should be reconsidered.
Planchet
Elisabeth
E
Lehrstuhl für Molekulare Pflanzenphysiologie und Biophysik Julius-von-Sachs Institute for Biosciences, University of Wuerzburg, Julius-von-Sachs-Platz 2, D-97082 Wuerzburg, Germany.
Sonoda
Masatoshi
M
Zeier
Jürgen
J
Kaiser
Werner M
WM
D020418:Algal Proteins / Q000494:pharmacology*; D001565:Benzoates / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects; D003497:Cyclic N-Oxides / Q000494:pharmacology; D005453:Fluorescence; D016166:Free Radical Scavengers / Q000378:metabolism; D005656:Fungal Proteins; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D007093:Imidazoles / Q000494:pharmacology; D050901:Nitrate Reductase / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D018515:Plant Leaves / Q000187:drug effects; D010940:Plant Proteins / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D014026:Nicotiana / Q000187:drug effects*
D020418:Algal Proteins; D001565:Benzoates; D003497:Cyclic N-Oxides; D016166:Free Radical Scavengers; D005656:Fungal Proteins; D007093:Imidazoles; D010940:Plant Proteins; D012333:RNA, Messenger; C061032:cryptogein protein, Phytophthora cryptogea; C079393:1,3-dihydroxy-4,4,5,5-tetramethyl-2-(4-carboxyphenyl)tetrahydroimidazole; C079392:2-phenyl 4,4,5,5-tetramethylimidazoline-1-oxyl; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D050901:Nitrate Reductase