Deinococcus radiodurans is a polyextremophilic bacterium well known for its extreme resistance to irradiation, oxidative stress, and other damaging conditions. Many small noncoding RNAs (ncRNAs) in D. radiodurans have been identified by deep sequencing analysis and computational predictions. However, the precise roles of ncRNAs and their target genes in the oxidative stress response have not been investigated. Here, we report the identification and characterization of a novel ncRNA named OsiR (for oxidative stress-induced ncRNA). Oxidative stress tolerance analysis showed that deleting osiR significantly decreased viability, total antioxidant capacity, and catalase activity in D. radiodurans under oxidative stress conditions. Comparative phenotypic and qRT-PCR analyses of an osiR mutant identify a role of OsiR in regulating the expression of the catalase gene katE2. Microscale thermophoresis and genetic complementation showed that a 21-nt sequence in the stem-loop structure of OsiR (204-244 nt) directly base pairs with its counterpart in the coding region of katE2 mRNA (843-866 nt) via a 19 nt region. In addition, deletion of katE2 caused a significant reduction of catalase activity and oxidative stress tolerance similar to that observed in an osiR mutant. Our results show that OsiR positively regulates oxidative stress tolerance in D. radiodurans by increasing the mRNA stability and translation efficiency of katE2. This work provides a new regulatory pathway mediated by ncRNA for the oxidative stress response that most likely contributes to the extreme tolerances of D. radiodurans.
Keywords: Deinococcus radiodurans; OsiR; katE2 mRNA; oxidative stress tolerance; small noncoding RNA.