Nitro-oxidative nucleotide modifications in plants and associated microorganisms: signalling sensors or stress symptoms?

Reactive oxygen and nitrogen species (ROS and RNS, respectively) play crucial roles in the functioning of plants and associated microorganisms. These molecules are engaged in signalling and gene regulatory events, and affect, among others, developmental processes and multilevel responses to unfavourable conditions. The ROS/RNS effects are frequently dependent on the oxidation/nitration of biomolecules. The increasing number of reports provide evidence for the formation of nitro-oxidative modifications in nucleotides, although their exact roles in plants and microorganisms are still vague. It is still unclear if nitration/oxidation of nucleotides is a symptom of damage resulting from an altered nitro-oxidative status or a sensing/signalling element for metabolism adjustment. The present review discusses the consequences and possible biological functions of nitrated/oxidized nucleic acids and cyclic nucleotides in plants and microorganisms.