Alternaria alternata AT Toxin Induces Programmed Cell Death in Tobacco |
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Authors: | Elena T. Yakimova Zhenya. P. Yordanova Slavtcho Slavov Veneta M. Kapchina-Toteva Ernst J. Woltering |
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Affiliation: | Authors' addresses: AgroBioInstitute, 8 Dragan Tzankov Blvd., 1164 Sofia, Bulgaria;;Faculty of Biology, University of Sofia, 8 Dragan Tzankov Blvd., 1164 Sofia, Bulgaria;;Wageningen University and Research Centre, Agrotechnology and Food Science Group (AFSG), PO Box 17, 6700 AA Wageningen, Netherlands (correspondence to Ernst J. Woltering. E-mail: ) |
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Abstract: | Detached tobacco leaves were infiltrated with an AT toxin preparation from the foliar pathogen Alternaria alternata tobacco pathotype. The AT toxin preparation caused formation of necrotic lesions within 5 days post-infiltration in a concentration-dependent manner. Cell death was accompanied by increased levels of the stress metabolites hydrogen peroxide, malondialdehyde, free proline and by enhanced total protease activity. Lesion development and the production of stress metabolites were suppressed if the infiltration site was pre-infiltrated with caspase-specific peptide inhibitors (irreversible caspase-1 inhibitor acyl-Tyr-Val-Ala-Asp-chloromethylketone (Ac-YVAD-CMK) and the broad range caspase inhibitor benzyoxycarbonyl-Asp-2,6-dichlorobenzoyloxymethylketone (Z-Asp-CH2-DCB)), the serine protease inhibitor Nα-p-tosyl- l -lysine chloromethylketone and the polyamine spermine. Extensive accumulation of reactive oxygen species (ROS), as determined by staining with 3-3'-diaminobenzidine and 2',7'-dichlorofluorescein diacetate, was found in the AT toxin-challenged lesions. The data show that AT toxin-induced cell death in tobacco is a type of programmed cell death in which caspase-like proteases and ROS signalling play a prominent role. |
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Keywords: | Alternaria alternata AT toxin Nicotiana tabacum oxidative stress programmed cell death proteolysis stress metabolites |
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