Role of protein and mRNA oxidation in seed dormancy and

Reactive oxygen species (ROS) are key players in the regulation of seed germination anddormancy. Although their regulated accumulation is a prerequisite for germination, thecellular basis of their action remains unknown, but very challenging to elucidate due tothe lack of specificity of these compounds that can potentially react with all biomolecules.Amongthese, nucleicacidsandproteinsareverypronetooxidativedamage. RNAishighlysensitive to oxidation because of its single-stranded structure and the absence of a repairsystem. Oxidation of mRNAs induces their decay through processing bodies or results inthe synthesis of aberrant proteins through altered translation. Depending on the oxidizedamino acid, ROS damage of proteins can be irreversible (i.e., carbonylation) thus triggeringthedegradationoftheoxidizedproteinsbythecytosolic20Sproteasomeorcanbereversedthrough the action of thioredoxins, peroxiredoxins, or glutaredoxins (cysteine oxidation) orby methionine sulfoxide reductase (methionine oxidation). Seed dormancy alleviation inthe dry state, referred to as after-ripening, requires both selective mRNA oxidation andprotein carbonylation. Similarly, seed imbibition of non-dormant seeds is associated withtargeted oxidation of a subset of proteins. Altogether, these specific features testify thatsuch oxidative modifications play important role in commitment of the cellular functioningtoward germination completion.