engleski

Dynamics of heat-shock induced DNA damage and repair in senescent tobacco plants

Oxidative stress plays an important role in the process of senescence or plant ageing as well as in response to different stressful environmental conditions. Given the importance of DNA integrity in preserving the homeostasis of an organism, oxidative DNA damage, unless repaired, may have detrimental consequences and increase genetic instability. Therefore, in this study we aimed to determine the role of heat-shock induced oxidative stress on induction and repair of DNA damage in relation to oxidative stress tolerance in senescent tobacco plants. One-month-old (young) and three-month-old (senescent) plants were exposed to 42 °C for 2 h and 4 h and left to recover at 26 °C for 72 h. The progression of senescence was characterized by the lower basal soluble protein and malondialdehyde content compared to young plants. Immediately after the heat shock exposure and subsequent 24 h recovery period, lipid peroxidation, an indicator of oxidative damage and guaiacol peroxidase activity, a nonspecific indicator of stress conditions, as well as DNA damage, measured by the Comet assay, were induced to higher extent in young plants than in senescent ones compared to their respective controls. Moreover, after recovery period of 24 h the DNA damage further increased in 1-month-old plants, whereas tendency of DNA repair was observed in 3-month-old plants. Upon 72 h of recovery period for all parameters examined in this study, regardless of plant age, no significant difference was noticed compared to controls. The random amplified polymorphic DNA (RAPD) analysis confirmed genetic stability of tobacco plants during heat-shock exposures as well as subsequent recovery periods. The present findings confirmed that tobacco plants regardless of their ages were able to counter heat stress in preventing genotoxicity of heat shock exposure.

Comet assay; DNA polymorphism; temperature stress; oxidative stress; RAPD

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