遗传 ›› 2015, Vol. 37 ›› Issue (3): 302-308.doi: 10.16288/j.yczz.14-291

• 研究报告 • 上一篇    下一篇

大肠杆菌TorS/TorR二组分体应答蛋白TorR对DNA复制起始的影响

姚远,乔佳鑫,李静,李慧,莫日根   

  1. 内蒙古大学生命科学学院,呼和浩特 010021
  • 收稿日期:2014-09-01 修回日期:2014-09-30 出版日期:2015-03-20 发布日期:2015-02-10
  • 通讯作者: 莫日根,博士,教授,博士生导师,研究方向:生物化学与分子生物学,DNA复制与细胞周期。E-mail: morigenm@life.imu.edu.cn E-mail:zhjyq129@163.com
  • 作者简介:姚远,在读博士研究生,专业方向:生物化学与分子生物学。E-mail:zhjyq129@163.com
  • 基金资助:
    国家自然科学基金项目(编号:31360208),内蒙古自然科学基金重大开放项目(编号:20102009)和内蒙古大学人才引进科研启动基金资助项目(编号:SPH-IMU, Z20090107)资助

The effects of TorR protein on initiation of DNA replication in Escherichia coli

Yuan Yao, Jiaxin Qiao, Jing Li, Hui Li, Morigen   

  1. School of Life Sciences, Inner Mongolia University, Hohhot 010021, China
  • Received:2014-09-01 Revised:2014-09-30 Online:2015-03-20 Published:2015-02-10

摘要: 二组分体作为一种信号转导系统在细菌中普遍存在,能够感知外界环境变化并做出应答。细菌中CckA/CtrA、ArcA/ArcB和PhoP/PhoQ二组分体与DNA复制起始和细胞分裂相关,但目前还未见TorS/TorR二组分体对细胞周期及DNA复制影响的相关报道。大肠杆菌TorS/TorR二组分体能够监测细胞周围氧化三甲胺(Trimethylamine oxide, TMAO)的浓度变化,但其是否影响DNA复制起始呢?文章利用流式细胞仪检测了ΔtorS和ΔtorR突变体菌株的复制式样。结果发现,ΔtorS突变菌株每个细胞复制起始原点数目和倍增时间与野生型细胞一致,而ΔtorR突变菌株每个细胞复制起始原点数目多于野生型细胞,说明复制起始发生时间比野生型细胞早。但是过表达TorR蛋白或者共同表达TorS和TorR蛋白都不能使ΔtorR突变体表型恢复为野生型表型。而在野生型和ΔtorR突变细胞中过表达SufD蛋白能使复制起始提早发生,在ΔtorR和ΔsufD双突变细胞中复制起始延迟。所以,TorR可能通过改变sufD基因的表达来间接影响染色体复制起始。

关键词: TorS/TorR二组分体, 应答蛋白TorR, DNA复制, 大肠杆菌

Abstract: The two-component systems, which could sense and respond to environmental changes, widely exist in bacteria as a signal transduction pathway. The bacterial CckA/CtrA, ArcA/ArcB and PhoP/PhoQ two-component systems are associated with initiation of DNA replication and cell division, however, the effects of the TorS/TorR system on cell cycle and DNA replication remains unknown. The TorS/TorR system in Escherichia coli can sense changes in trimethylamine oxide (TMAO) concentration around the cells. However, it is unknown if it also affects initiation of DNA replication. We detected DNA replication patterns in ΔtorS and ΔtorR mutant strains by flow cytometry. We found that the average number of replication origins (oriCs) per cell and doubling time in ΔtorS mutants were the same while the average number of oriCs in ΔtorR mutants was increased compared with that in wild-type cells. These results indicated that absence of TorR led to an earlier initiation of DNA replication than that in wild-type cells. Strangely, neither overexpression of TorR nor co-expression of TorR and TorS could restore ΔtorR mutant phenotype to the wild type. However, overexpression of SufD in both wild type and ΔtorR mutants promoted initiation of DNA replication, while mutation of SufD delayed it in ΔtorR mutants. Thus, TorR may affect initiation of DNA replication indirectly through regulating gene expression of sufD.

Key words: TorS/TorR two-component system, the response regulator TorR, DNA replication, Escherichia coli