副溶血性弧菌整合接合元件核心基因表达对温度变化的响应

Effect of Temperature on the Expression of Core Genes of Integrative and Conjugative Elements in Vibrio parahaemolyticus

采用实时荧光定量聚合酶链式反应方法分析在1 5~4 2℃温度范围内副溶血性弧菌（Vi b r i o parahaemolyticus）CHN25整合接合元件（integrative and conjugative elements,ICEs）ICEVpa Chn1核心基因表达对温度变化的响应。结果表明：温度介导ICEVpa Chn1元件保守模块核心基因表达发生显著变化,其中,编码进入排斥蛋白Eex（entry exclusion）的基因对温度变化最为敏感,低于或高于37℃的温度条件均强烈抑制eex基因表达（〉10倍）。此外,在15~37℃范围内,温度的升高显著激活编码整合酶Int（integrase）、接合转移蛋白Tra I（transfer protein I）和Tra G、DNA修复蛋白Rum A基因的表达,且在37℃达到最大值;与其他检测基因明显不同,温度升高抑制转录抑制子Set R基因的表达,促进int等基因转录激活子Set C和Set D的积累,进而刺激切离,促进ICEVpa Chn1元件的接合转移。实验结果揭示了环境温度对ICEs元件核心基因表达的影响,发现低温（〈15℃）和高温（〉37℃）条件均可能阻遏ICEVpa Chn1元件及其携带基因信息在不同种属细菌间的接合转移。

In this study,for the first time,we investigated the effect of temperature（15–42 ℃） on the expression of core genes of the integrative and conjugative element（ICE,ICEVpa Chn1） in Vibrio parahaemolyticus CHN25 using real time polymerase chain reaction（real-time PCR）.The results revealed distinct expression patterns of the tested genes.The eexgene involved in the entry exclusion system was strongly inhibited by more than 10 folds when the bacterium was incubated at the temperatures below or above 37 ℃.Along with increasing temperature in the range of 15–37 ℃,the expression of int,tra I,rum A,and tra G genes was enhanced,and reached the highest level at 37 ℃ as the optimal growth temperature forV.parahaemolyticus CHN25.In contrast,increasing temperature could significantly repress the expression of the gene encoding a repressor protein Set R that can stimulate the activators of the int gene（Set C and Set D） and promote the conjugation and transfer of ICEVpa Chn1.In addition,self-transmissible activity of the ICE was likely inhibited when the bacterium was grown at temperatures lower than 15 ℃ or above 37 ℃.The results of this study will facilitate better understanding of the molecular mechanism underlying the effects of environment stresses on the conjugative transfer of ICEs.