Characterization and expression analysis of three cold shock protein (CSP) genes under different stress conditions in the Antarctic bacterium Psychrobacter sp G

Low temperature is one of the major environmental challenges that Antarctic bacteria must face. Detailed studies of cold shock responses of cold-adapted microorganisms are still insufficient. Here, we cloned three cold shock protein (CSP) genes (Csp1137, Csp2039, and Csp2531) in the Antarctic bacterium Psychrobacter sp. G and their regulatory sequences were identified. The three CSPs were highly conserved with other known CspAs. qRT-PCR was performed to evaluate their expression characteristics under stress conditions, and the potential influence of regulatory sequences also was analyzed. The expression of Csp1137 was enhanced both by low (0, 10 A degrees C) and high temperature (30 A degrees C). The expression of Csp2039 was enhanced by low temperature (0 A degrees C), but was lower than that of Csp1137. This can be explained by the absence in Csp2039 of the AT-rich UP element. Different from Csp1137, the expression of Csp2531 was inhibited by low temperature (0 A degrees C), even with the presence of AT-rich UP element, and it was not sensitive to high temperature (30 A degrees C). The expression of Csp1137 was enhanced by high salinity (90, 120), whereas that of Csp2531was enhanced by low salinity (0, 15). At 0 A degrees C and a salinity of 15, the expression of Csp1137 was repressed initially, but then it increased greatly during the next 10 h. The expressions of Csp2039 and Csp2531 were repressed significantly under four different combinations of stress conditions. Our results showed that the role of the upstream regulation sequences were much more complex than previously thought. Also, gene expressions were also affected by the environmental salinity. These are helpful in further clarification of the adaptation mechanism of Psychrobacter sp. G.