Genetic Interactions of smc, ftsK, and parB Genes in Streptomyces coelicolor and Their Developmental Genome Segregation Phenotypes
Genetic Interactions of smc, ftsK, and parB Genes in Streptomyces coelicolor and Their Developmental Genome Segregation Phenotypes
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DOI：
10.1128/jb.00858-08
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发表时间：
2009-01-01
影响因子：
3.2
通讯作者：
McCormick, Joseph R.
中科院分区：
文献类型：
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作者：
Dedrick, Rebekah M.;Wildschutte, Hans;McCormick, Joseph R.
染色体在发育调控的细胞分裂过程中凝聚和分离的机制是天蓝色链霉菌（Streptomyces coelicolor）感兴趣的，天蓝色链霉菌是一种具有大型线性基因组的孢子形成丝状细菌。这些过程协调地发生，因为许多隔膜在合胞气生菌丝中同步形成，使得前孢子隔室准确地接收染色体拷贝。我们的遗传方法分析了ftsK、smc和parB的突变体。DNA马达蛋白FtsK/SpoIIIE在杆状细菌中协调染色体分离与隔膜闭合。SMC（染色体结构维持）参与类核的凝聚和组织。ParB/Spo 0 J使用在着丝粒样序列处组装的核蛋白复合物划分复制起点。与之前的工作一致，我们表明ftsK无效突变体产生无核孢子的频率与野生型菌株相同（0.8%）。我们报道了smc和ftsK缺失-插入突变体（ftsK'截短等位基因）具有发育分离缺陷（分别为7%和15%的无核孢子）。通过使用这些后面的突变体，在与先前描述的parB无效突变体（12%无核孢子）的所有组合中分离出了可行的双重和三重突变体。parB和smc是在单独的分离途径;两者的损失加剧了分离缺陷（24%无核孢子）。对于三重突变体，缺失编码FtsK马达结构域的区域和一个跨膜区段部分地消除了smc parB突变体的分离缺陷（10%无核孢子）。这种丝状生物中一定存在相当大的冗余，因为在发育过程中90%的时间内，一些基因组物质会发生分离，缺乏三种功能，孢子活力仅损失四倍。此外，我们报告，scpA和scpAB突变体（编码SMC相关蛋白）有孢子类核组织缺陷。最后，FtsK增强的绿色荧光蛋白（EGFP）定位为初始类核之间的带或焦点，而SMC-EGFP焦点并不均匀地定位沿着气生菌丝，也不与每一个浓缩的类核。
The mechanisms by which chromosomes condense and segregate during developmentally regulated cell division are of interest for Streptomyces coelicolor, a sporulating, filamentous bacterium with a large, linear genome. These processes coordinately occur as many septa synchronously form in syncytial aerial hyphae such that prespore compartments accurately receive chromosome copies. Our genetic approach analyzed mutants for ftsK, smc, and parB. DNA motor protein FtsK/SpoIIIE coordinates chromosome segregation with septum closure in rod-shaped bacteria. SMC (structural maintenance of chromosomes) participates in condensation and organization of the nucleoid. ParB/Spo0J partitions the origin of replication using a nucleoprotein complex, assembled at a centromere-like sequence. Consistent with previous work, we show that an ftsK-null mutant produces anucleate spores at the same frequency as the wild-type strain (0.8%). We report that the smc and ftsK deletion-insertion mutants (ftsK' truncation allele) have developmental segregation defects (7% and 15% anucleate spores, respectively). By use of these latter mutants, viable double and triple mutants were isolated in all combinations with a previously described parB-null mutant (12% anucleate spores). parB and smc were in separate segregation pathways; the loss of both exacerbates the segregation defect (24% anucleate spores). For a triple mutant, deletion of the region encoding the FtsK motor domain and one transmembrane segment partially alleviates the segregation defect of the smc parB mutant (10% anucleate spores). Considerable redundancy must exist in this filamentous organism because segregation of some genomic material occurs 90% of the time during development in the absence of three functions with only a fourfold loss of spore viability. Furthermore, we report that scpA and scpAB mutants (encoding SMC-associated proteins) have spore nucleoid organization defects. Finally, FtsK-enhanced green fluorescent protein (EGFP) localized as bands or foci between incipient nucleoids, while SMC-EGFP foci were not uniformly positioned along aerial hyphae, nor were they associated with every condensing nucleoid.