The complete sequence and functional analysis of pANL, the large plasmid of the unicellular freshwater cyanobacterium Synechococcus elongatus PCC 7942
The complete sequence and functional analysis of pANL, the large plasmid of the unicellular freshwater cyanobacterium Synechococcus elongatus PCC 7942
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DOI：
10.1016/j.plasmid.2008.01.005
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发表时间：
2008-05-01
期刊：
影响因子：
2.6
通讯作者：
Golden, Susan S.
中科院分区：
文献类型：
--
作者：
Chen, You;Holtman, C. Kay;Golden, Susan S.
在研究蓝藻光合作用和昼夜节律的模式生物——长聚球菌PCC 7942中存在两个内源性质粒。大质粒pANL先前被证明参与了S. elongatus细胞对硫饥饿的适应，这为蓝藻质粒的细胞功能提供了第一个证据。在这里，我们报道了完整的pANL序列，长度为46,366 bp， GC含量为53%，编码58个假定的orf。pANL质粒可分为4个结构和功能区：复制起始区、信号转导区、质粒维持区和硫调控区。基于cosmid的缺失分析表明，质粒维持区和复制起始区是pANL在细胞中持续存在的必要条件。转座子介导的突变和互补。pANL分离实验证实，在质粒维持区编码的两个预测毒素-抗毒素磁带，分别属于PemK和VapC家族，是质粒排除所必需的。硫相关基因在pANL上紧凑而高效的组织可能在硫有限的环境中具有选择优势。(c) 2008爱思唯尔公司版权所有。
Two endogenous plasmids are present in Synechococcus elongatus PCC 7942, a model organism for studying photosynthesis and circadian rhythms in cyanobacteria. The large plasmid, pANL, was shown previously to be involved in adaptation of S. elongatus cells to sulfur starvation, which provided the first evidence of cellular function of a cyanobacterial plasmid. Here, we report the complete sequence of pANL, which is 46,366 bp in length with 53% GC content and encodes 58 putative ORFs. The pANL plasmid can be divided into four structural and functional regions: the replication origin region, a signal transduction region, a plasmid maintenance region, and a sulfur-regulated region. Cosmid-based deletion analysis suggested that the plasmid maintenance and replication origin regions are required for persistence of pANL in the cells. Transposon-mediated mutagenesis and complementation-based. pANL segregation assays confirmed that two predicted toxin-antitoxin cassettes encoded in the plasmid maintenance region, belonging to PemK and VapC families, respectively, are necessary for plasmid exclusion. The compact and efficient organization of sulfur-related genes on pANL may provide selective advantages in environments with limited sulfur. (c) 2008 Elsevier Inc. All rights reserved.