Functional activity of E. coli RNase R in the Antarctic Pseudomonas syringae Lz4W

Background In Antarctic P. syringae RNase R play an essential role in the processing of 16S and 5S rRNA, thereby playing an important role in cold-adapted growth of the bacterium. This study is focused on deciphering the in vivo functional activity of mesophilic exoribonuclease R and its catalytic domain (RNB) in an evolutionary distant psychrophilic bacterium Pseudomonas syringae Lz4W.Results Our results confirm that E. coli RNase R complemented the physiological functions of the psychrophilic bacterium P. syringae RNase R and rescued the cold-sensitive phenotype of Pseudomonas syringae triangle rnr mutant. More importantly, the catalytic domain (RNB) of the E. coli RNase R is also capable of alleviating the cold-sensitive growth defects of triangle rnr mutant as seen with the catalytic domain (RNB) of the P. syringae enzyme. The Catalytic domain of E. coli RNase R was less efficient than the Catalytic domain of P. syringae RNase R in rescuing the cold-sensitive growth of triangle rnr mutant at 4 degrees C, as the triangle rnr expressing the RNBEc (catalytic domain of E. coli RNase R) displayed longer lag phase than the RNBPs (Catalytic domain of P. syringae RNase R) complemented triangle rnr mutant at 4 degrees C. Altogether it appears that the E. coli RNase R and P. syringae RNase R are functionally exchangeable for the growth requirements of P. syringae at low temperature (4 degrees C). Our results also confirm that in P. syringae the requirement of RNase R for supporting the growth at 4 degrees C is independent of the degradosomal complex.Conclusion E. coli RNase R (RNase R-Ec) rescues the cold-sensitive phenotype of the P. syringae Delta rnr mutant. Similarly, the catalytic domain of E. coli RNase R (RNBEc) is also capable of supporting the growth of Delta rnr mutant at low temperatures. These findings have a vast scope in the design and development of low-temperature-based expression systems.