NO way back: nitric oxide and programmed cell death in Arabidopsis thaliana suspension cultures.
Recent research has implicated nitric oxide (NO) in the induction of the hypersensitive response (HR) during plant-pathogen interactions. Here we demonstrate that Arabidopsis suspension cultures generate elevated levels of NO in response to challenge by avirulent bacteria, and, using NO donors, show that these elevated levels of NO are sufficient to induce cell death in Arabidopsis cells independently of reactive oxygen species (ROS). We also provide evidence that NO-induced cell death is a form of programmed cell death (PCD), requiring gene expression, and has a number of characteristics of PCD of mammalian cells: NO induced chromatin condensation and caspase-like activity in Arabidopsis cells, while the caspase-1 inhibitor, Ac-YVAD-CMK, blocked NO-induced cell death. A well-established second messenger mediating NO responses in mammalian cells is cGMP, produced by the enzyme guanylate cyclase. A specific inhibitor of guanylate cyclase blocked NO-induced cell death in Arabidopsis cells, and this inhibition was reversed by the cell-permeable cGMP analogue, 8Br-cGMP, although 8Br-cGMP alone did not induce cell death or potentiate NO-induced cell death. This suggests that cGMP synthesis is required but not sufficient for NO-induced cell death in Arabidopsis. In-gel protein kinase assays showed that NO activates a potential mitogen-activated protein kinase (MAPK), although a specific inhibitor of mammalian MAPK activation, PD98059, which blocked H2O2-induced cell death, did not inhibit the effects of NO.
Clarke
A
A
Centre for Research in Plant Science, University of the West of England, Bristol Coldharbour Lane, Bristol BS16 1QY, UK.
Desikan
R
R
Hurst
R D
RD
Hancock
J T
JT
Neill
S J
SJ
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D017360:Arabidopsis / Q000166:cytology / Q000378:metabolism* / Q000382:microbiology; D002843:Chromatin / Q000187:drug effects / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D005419:Flavonoids / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000378:metabolism / Q000494:pharmacology; D058085:Iron Compounds / Q000494:pharmacology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D009603:Nitroso Compounds / Q000494:pharmacology; D011549:Pseudomonas / Q000235:genetics / Q000472:pathogenicity; D017382:Reactive Oxygen Species / Q000378:metabolism; D013997:Time Factors; D014774:Virulence / Q000235:genetics
D000590:Amino Acid Chloromethyl Ketones; D002843:Chromatin; D015853:Cysteine Proteinase Inhibitors; D005419:Flavonoids; D058085:Iron Compounds; C098738:N-acetyl-tyrosyl-valyl-alanyl-aspartyl chloromethyl ketone; D020030:Nitric Oxide Donors; D009603:Nitroso Compounds; D017382:Reactive Oxygen Species; D009599:Nitroprusside; D009569:Nitric Oxide; C078952:Roussin's Black Salt; D006861:Hydrogen Peroxide; D020928:Mitogen-Activated Protein Kinases; D006152:Cyclic GMP; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one