Trancriptomic Analysis Of The Antarctic Psychrotrophic Bacterium Psychrobacter Sp. G And Expression Characteristics Of Heat Shock Protein Gene (hsp845)/Cold Shock Protein Gene(Csp2039)

Antarctic ecosystem is characterized by extreme cold, dry, poor nutrient availability andstrong radiation. Although few animals and plants exist, there are abundant of microorganismswhich play vital roles in the material circlulation of the Antarctic ecosystem. Genome andtranscriptome sequencing were performed to obtain the key functional genes involved in the lowtemperature adaption of Antarctic psychrotrophic bacterium Psychrobacter sp. G. The expressioncharacteristics of cold shock protein gene （Csp2039） and heat shock protein gene （Hsp845） wereevaluated by qRT-PCR and western blot under different temperature/salinity stresses in bothtranscriptional and translational pattern, respectively. The study is helpful to clarify the adaptionmechanism of Psychrobacter sp. G in the severe environment of Antarctica.The complete genome of Psychrobacter sp. G contained one circle chromosome and threeplasmids （Psy_G26, Psy_G4and Psy_G3）. The full lengh of chromosome was3,079,438bp with42.44%content of G+C. The complete chromsome contained2578ORFs with homologs inGenbank, and1862of them were annotated by Blast2GO program. The GO annotation showedthat91ORFs were related to cellular response to stimulus and73ORFs were involved in responseto stress. Hsp845（PSYCG₁3305, which belonged to GrpE family） and Csp2039（PSYCG₀2930,which belonged to CspA family） were selected to study their response characteristics underdifferent temperature/salinity stresses in both transcriptional and translational pattern,respectively.The result of RNA-seq showed that we obtained21,332,482reads with2,094,022,257bpunder optimal condition （C,20℃）,20,153,164reads with197,7682,536bp under hightemperature stress （H,30℃） and23,352,554reads with2,293,153,422bp under low temperaturestress （L,0℃）, respectively from the transcriptome sequencing of Psychrobacter sp. G. The comparative analysis showed that, after exposed to high temperature, the expression of1345geneswere upregulated,12of which were significant;1278genes were downregulated,48of whichwere significant. While being exposed to low temperature, the expression of1266genes wereupregulated,11genes of whcih were significant;1345genes were downregulated and46of themwith significance.The expression of Hsp845was induced by high temperature （30℃） in both transcriptionaland translational, patterns; it was also induced by both low （0） and high salinity （90and120） intranscriptional pattern. However, the expression was only induced by high salinity （90and120） intranslational pattern. The expression of Hsp845was more sensitive to high temperature stress thanto salinity stress in both transcriptional and translational patterns, and the maximum expression ofHsp845in translational pattern was lagged compared with that of the transcriptional pattern. Themaximum expression level of transcription was also higher than that of translational pattern. Thetranscriptional results under the salinity of0seemed contrary to the results of translational pattern,and the mechanism is still needed for further study. In single factor experiment （only withdifferent temperature or salinity stress）, the expression of Hsp845was enhanced much more bysalinity than that of the temperature, however, under the combined stress, temperature seemedmore important than salinity, and the mechanism is still needed to study further.The expression of Csp2039was induced by low temperature （0,10℃） in both transcriptionaland translational patterns. Because of the wide induced temperature range of CspA family, theexpression was also induced by high temperature （30℃）. In transcriptional pattern, high salinity（90and120） inhabited the expression of Csp2039significantly and low salinity （0and15） seemedto have no effect on it. However, in translational pattern, both high and low salinity enhanced theexpression of Csp2039significantly. In single factor experiment （only with different temperatureor salinity stress）, the expression of Csp2039was enhanced by temperature much more than thatof the salinity in transcriptional pattern. However, under the combined stress, salinity seemedmore effective than temperature in translational pattern, and the mechanism is still needed to studyfurther.