Ozone-induced cell death in tobacco cultivar Bel W3 plants. The role of programmed cell death in lesion formation.
Treatment of the ozone-sensitive tobacco (Nicotiana tabacum L. cv Bel W3) with an ozone pulse (150 nL L(-1) for 5 h) induced visible injury, which manifested 48 to 72 h from onset of ozone fumigation. The "classical" ozone symptoms in tobacco cv Bel W3 plants occur as sharply defined, dot-like lesions on the adaxial side of the leaf and result from the death of groups of palisade cells. We investigated whether this reaction had the features of a hypersensitive response like that which results from the incompatible plant-pathogen interaction. We detected an oxidative burst, the result of H2O2 accumulation at 12 h from the starting of fumigation. Ozone treatment induced deposition of autofluorescent compounds and callose 24 h from the start of treatment. Total phenolic content was also strongly stimulated at the 10th and 72nd h from starting fumigation, concomitant with an enhancement in phenylalanine ammonia-lyase a and phenylalanine ammonia-lyase b expression, as evaluated by reverse transcriptase-polymerase chain reaction. There was also a marked, but transient, increase in the mRNA level of pathogenesis-related-1a, a typical hypersensitive response marker. Overall, these results are evidence that ozone triggers a hypersensitive response in tobacco cv Bel W3 plants. We adopted four criteria for detecting programmed cell death in ozonated tobacco cv Bel W3 leaves: (a) early release of cytochrome c from mitochondria; (b) activation of protease; (c) DNA fragmentation by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling of DNA 3'-OH groups; and (d) ultrastructural changes characteristic of programmed cell death, including chromatin condensation and blebbing of plasma membrane. We, therefore, provide evidence that ozone-induced oxidative stress triggers a cell death program in tobacco cv Bel W3.
Pasqualini
Stefania
S
Dipartimento di Biologia Vegetale e Biotecnologie Agroambientali, Università degli Studi di Perugia, Borgo XX Giugno, 74-06121 Perugia, Italy. antmfisveg@unipg.it
Piccioni
Claudia
C
Reale
Lara
L
Ederli
Luisa
L
Della Torre
Guido
G
Ferranti
Francesco
F
D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002455:Cell Division / Q000187:drug effects; D045304:Cytochromes c / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D010450:Endopeptidases / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D020287:In Situ Nick-End Labeling; D008928:Mitochondria / Q000378:metabolism; D010126:Ozone / Q000494:pharmacology*; D018515:Plant Leaves / Q000187:drug effects / Q000254:growth & development*; D010940:Plant Proteins / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D016897:Respiratory Burst / Q000187:drug effects; D014026:Nicotiana / Q000187:drug effects / Q000235:genetics / Q000254:growth & development*
D010940:Plant Proteins; D017382:Reactive Oxygen Species; C053376:pathogenesis-related proteins, plant; D010126:Ozone; D045304:Cytochromes c; D006861:Hydrogen Peroxide; D010450:Endopeptidases