Nitric oxide (NO) as an intermediate in the cryptogein-induced hypersensitive response--a critical re-evaluation |
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Authors: | Planchet Elisabeth Sonoda Masatoshi Zeier Jürgen Kaiser Werner M |
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Institution: | Lehrstuhl für Molekulare Pflanzenphysiologie und Biophysik Julius-von-Sachs Institute for Biosciences, University of Wuerzburg, Julius-von-Sachs-Platz 2, D-97082 Wuerzburg, Germany. |
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Abstract: | 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. |
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Keywords: | Nicotiana tabacum chemiluminescence detection cryptogein DAF-2DA hypersensitive response nitrate reductase nitric oxide nitric oxide synthase |
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