Exoribonuclease RNase R protects Antarctic Pseudomonas syringae Lz4W from DNA damage and oxidative stress.

IMPORTANCE: Bacterial exoribonucleases play a crucial role in RNA maturation, degradation, quality control, and turnover. In this study, we have uncovered a previously unknown role of 3'-5' exoribonuclease RNase R of Pseudomonas syringae Lz4W in DNA damage and oxidative stress response. Here, we show that neither the exoribonuclease function of RNase R nor its association with the RNA degradosome complex is essential for this function. Interestingly, in P. syringae Lz4W, hydrolytic RNase R exhibits physiological roles similar to phosphorolytic 3'-5' exoribonuclease PNPase of E. coli. Our data suggest that during the course of evolution, mesophilic E. coli and psychrotrophic P. syringae have apparently swapped these exoribonucleases to adapt to their respective environmental growth conditions.