The aim of the planned experiment is the comparative study of the role of the antioxidants and poly(ADP-ribose) polymerase (PARP) in the abiotic stress-induced senescence using stress-tolerant and -sensitive cereals.

The reactive oxygen species may be accumulated because of the different abiotic stress effects. If the antioxidant system (ascorbate-glutathione cycle, catalase) will be activated sufficiently and the stress is not to severe, the plants can be regenerate the damages after the unfavorable conditions. If the abiotic stress effects are to strong and the antioxidant system is not able to ensure the balance between the production and removal of the reactive oxygen species (superoxide and hydroxyl radicals, hydrogen peroxide), the senescence may start, and in extreme situations the cells may die. The reactive oxygen species accumulated cause injuries in the cells because of their harmful effects on vital macromolecules. The hydroxyl radical induces the fragmentation of the DNA molecules, which process in turn activates the PARP. The activation of the PARP may cause the death of the cells because of the exhaustion of the NAD⁺ pool, which is an important energy source in the cell. In the research program the activation of the antioxidants and PARP will be studied in cereals subjected of abiotic stresses (high and low temperatures, high salt concentrations, osmotic stress) of different strength. By manipulation of the antioxidants and PARP using specific inducers and inhibitors the alteration in the stress tolerance and senescence and the possible interaction between antioxidants and PARP will be studied. The investigation of antioxidants and PARP is planned at the level mRNA, protein and enzyme activity. The changes in the ratio of reduced and oxidized glutathione and ascorbate will be also determined. From the reactive oxygen species the amount of hydrogen peroxide will be measured. The level of senescence will be proved by the measurement of lipid peroxidation and electrolyte leakage. Wheat and maize genotypes having different stress tolerance will be compared. We plan the mapping of the parameters studied using our specific wheat genetic material. The predicted theoretical benefit of the program is the elucidation of the role of the antioxidants and PARP in the stress adaptation and in the senescence processes of plants. A practical use of the results can be the manipulation of the level of PARP and antioxidants in order to improve the stress tolerance of the cereals by inhibition of the stress-induced senescence.