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Oxidation of RNA is associated with the development of numerous disorders including Alzheimer's and Parkinson's diseases, amyotrophic lateral sclerosis (ALS), cancer, and diabetes. Additionally, a correlation has been found between increase in RNA oxidation and the process of aging. In plants, elevated level of oxidatively modified transcripts has been detected during alleviation of seeds dormancy and stress response. Increasing interest on the topic of RNA oxidative modifications requires elaboration of new laboratory techniques. So far, the most common method used for the assessment of RNA oxidation is quantification of 8-hydroxyguanine (8-OHG). However, reactive oxygen species (ROS) induce also numerous other changes in nucleic acids, including formation of abasic sites (AP-sites). Recently, the level of AP-sites in RNA has been measured with the use Aldehyde Reactive Probe (ARP). In the present chapter, we describe application of this technique for the evaluation of the level of AP-sites in plant transcripts.

Nitro-oxidative modifications of biomolecules result from the presence of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in the cellular environment. Unlike ROS/RNS-mediated modifications of proteins and fatty acids, nucleotides embedded in nucleic acids have not been a major focus of studies on nitro-oxidative metabolism in plants. However, RNA structure being more susceptible to oxidative/nitrative attack than DNA can be considered as an important functional biotarget of ROS/RNS generated under both physiological and stress conditions. The formation of 8-hydroxyguanine (8-OHG) and 8-nitroguanine (8-NG), the most common ROS- and RNS-mediated RNA modifications, respectively, could therefore affect protein synthesis to efficiently fine-tune various cellular responses. This chapter emphasizes the importance of 8-OHG and 8-NG not only as a symptom of ROS/RNS toxicity but implicates the nitro-oxidative RNA modifications in the regulation of multiple plant biological processes.

Heavy metal pollution causes many soils to become a toxic environment not only for plants, but also microorganisms, however, little is known how heavy metal contaminated environment affects metabolism of phytopathogens and their capability of infecting host plants. In this study the oomycete Phytophthora infestans (Mont.) de Bary, the most harmful pathogen of potato, growing under moderate cadmium stress (Cd, 5 mg/L) showed nitro-oxidative imbalance associated with an enhanced antioxidant response. Cadmium notably elevated the level of nitric oxide, superoxide and peroxynitrite that stimulated nitrative modifications within the RNA and DNA pools in the phytopathogen structures. In contrast, the protein pool undergoing nitration was diminished confirming that protein tyrosine nitration is a flexible element of the oomycete adaptive strategy to heavy metal stress. Finally, to verify whether Cd is able to modify P. infestans pathogenicity, a disease index and molecular assessment of disease progress were analysed indicating that Cd stress enhanced aggressiveness of vr P. infestans towards various potato cultivars. Taken together, Cd not only affected hyphal growth rate and caused biochemical changes in P. infestans structures, but accelerated the pathogenicity as well. The nitro-oxidative homeostasis imbalance underlies the phytopathogen adaptive strategy and survival in the heavy metal contaminated environment.