Chitosan-induced programmed cell death in plants |
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Authors: | L A Vasil’ev E V Dzyubinskaya R A Zinovkin D B Kiselevsky N V Lobysheva V D Samuilov |
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Institution: | (1) Department of Physiology of Microorganisms, Biological Faculty, Lomonosov Moscow State University, 119991 Moscow, Russia |
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Abstract: | Chitosan, CN−, or H2O2 caused the death of epidermal cells (EC) in the epidermis of pea leaves that was detected by monitoring the destruction of
cell nuclei; chitosan induced chromatin condensation and marginalization followed by the destruction of EC nuclei and subsequent
internucleosomal DNA fragmentation. Chitosan did not affect stoma guard cells (GC). Anaerobic conditions prevented the chitosan-induced
destruction of EC nuclei. The antioxidants nitroblue tetrazolium or mannitol suppressed the effects of chitosan, H2O2, or chitosan + H2O2 on EC. H2O2 formation in EC and GC mitochondria that was determined from 2′,7′-dichlorofluorescein fluorescence was inhibited by CN− and the protonophoric uncoupler carbonyl cyanide m-chlorophenylhydrazone but was stimulated by these agents in GC chloroplasts. The alternative oxidase inhibitors propyl gallate
and salicylhydroxamate prevented chitosan- but not CN−-induced destruction of EC nuclei; the plasma membrane NADPH oxidase inhibitors diphenylene iodonium and quinacrine abolished
chitosan- but not CN−-induced destruction of EC nuclei. The mitochondrial protein synthesis inhibitor lincomycin removed the destructive effect
of chitosan or H2O2 on EC nuclei. The effect of cycloheximide, an inhibitor of protein synthesis in the cytoplasm, was insignificant; however,
it was enhanced if cycloheximide was added in combination with lincomycin. The autophagy inhibitor 3-methyladenine removed
the chitosan effect but exerted no influence on the effect of H2O2 as an inducer of EC death. The internucleosome DNA fragmentation in conjunction with the data on the 3-methyladenine effect
provides evidence that chitosan induces programmed cell death that follows a combined scenario including apoptosis and autophagy.
Based on the results of an inhibitor assay, chitosan-induced EC death involves reactive oxygen species generated by the NADPH
oxidase of the plasma membrane. |
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