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An analysis of the expression, function, and evolution of the FtsZ plastid division genes.

机译：FtsZ质体分裂基因的表达，功能和进化分析。

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摘要

The photosynthetic capabilities of plants cells are dependent on the presence and maintenance of chloroplasts. The chloroplast complement of higher plant mesophyll cells, often very numerous, is maintained by division as cells differentiate and expand. Chloroplasts are evolutionarily derived from cyanobacteria through an endosymbiotic event and continue to bear several ancestral characteristics. The prokaryotic origins became even more evident when a chloroplast-targeted homologue of the bacterial cell division protein FtsZ was identified in plants. In bacteria, FtsZ is the first known protein to assemble at the division site. FtsZ has GTPase activity and polymerizes into a ring that encircles the cell at the cyoplasmic membrane surface. Following assembly of the FtsZ ring at the division site, several other proteins are recruited for assembly of a functional cell division apparatus.;In contrast to most bacteria that encode a single FtsZ gene, plants have multiple nuclear encoded FtsZ proteins that are localized to the chloroplast. The plant homologues have been grouped into two families, FtsZ1 and FtsZ2, based on sequence comparisons. Arabidopsis plants express three different FtsZ homologues: one FtsZ1 family member, AtFtsZ1-1, and two FtsZ2 family members, AtFtsZ2-1 and AtFtsZ2-2. Antisense repression experiments indicate members of both families are required for chloroplast division, suggesting that chloroplasts have evolved a more complex division apparatus than is present in bacteria.;In an effort to better understand the role of the FtsZ1 and FtsZ2 proteins in chloroplast division, experiments were designed to investigate their function, expression, and evolution. To investigate some of the FtsZ functions in plastid division, the FtsZ proteins were overexpressed in Arabidopsis and the effects on chloroplast division were observed. The results indicate a stoichiometric balance is required for division and that disruption of that balance inhibits chloroplast division. Experiments with promoter-GUS fusion constructs were used to determine where and when FtsZ is expressed in Arabidopsis. Some of the FtsZ expression patterns were confirmed by measuring the cDNA distribution patterns. The results indicate the three FtsZ homologues are coordinately expressed in several plant tissues including roots, meristems, and young leaves. FtsZ expression occurs in tissue regions with rapidly dividing chloroplast populations and is consistent with the role of FtsZ in chloroplast division.;In an effort to understand when and why chloroplasts evolved two FtsZ families, we performed phylogenetic analyses, compared genetic structures, and compared conserved protein sequences. Phylogenetic analyses indicate the FtsZ1 and FtsZ2 sequences diverged before the split between the chlorophycean and charophycean green algal lineages and possibly earlier. Genetic structure comparisons reveal intron positions are conserved within the FtsZ1 and FtsZ2 family members but differ between them, also supporting an early divergence. Comparison of conserved protein sequences indicated several regions in which the FtsZ1 and FtsZ2 family members differ. These conserved differences may define functional differences between the FtsZ1 and FtsZ2 proteins.
机译：植物细胞的光合作用能力取决于叶绿体的存在和维持。高等植物叶肉细胞的叶绿体补体通常非常多，随着细胞的分化和扩展而分裂而得以维持。叶绿体通过内共生事件从蓝细菌进化衍生而来，并继续具有一些祖先特征。当在植物中鉴定到细菌细胞分裂蛋白FtsZ的叶绿体靶向同源物时，原核起源就变得更加明显。在细菌中，FtsZ是第一个在分裂位点组装的已知蛋白质。 FtsZ具有GTPase活性，并聚合成环，在细胞质膜表面环绕细胞。在分裂位点组装FtsZ环后，募集了其他几种蛋白质用于功能细胞分裂装置的组装。与大多数编码单个FtsZ基因的细菌相反，植物具有多个核编码的FtsZ蛋白，这些蛋白位于叶绿体。基于序列比较，植物同源物已分为两个家族，即FtsZ1和FtsZ2。拟南芥植物表达三种不同的FtsZ同源物：一个FtsZ1家族成员AtFtsZ1-1和两个FtsZ2家族成员AtFtsZ2-1和AtFtsZ2-2。反义抑制实验表明叶绿体分裂需要两个家族的成员，这表明叶绿体已经进化出了比细菌中存在的更复杂的分裂装置。为了更好地理解FtsZ1和FtsZ2蛋白在叶绿体分裂中的作用，进行了实验旨在研究其功能，表达和进化。为了研究FtsZ在质体分裂中的某些功能，在拟南芥中过表达FtsZ蛋白并观察到对叶绿体分裂的影响。结果表明需要化学计量的平衡才能进行分离，破坏该平衡会抑制叶绿体的分裂。用启动子-GUS融合构建体进行的实验确定了FtsZ在拟南芥中的表达位置和时间。通过测量cDNA分布模式可以确认某些FtsZ表达模式。结果表明，三个FtsZ同源物在根，分生组织和幼叶等几种植物组织中协调表达。 FtsZ表达发生在快速分裂的叶绿体群体的组织区域中，并且与FtsZ在叶绿体分裂中的作用一致。为了了解叶绿体何时和为何进化两个FtsZ家族，我们进行了系统进化分析，比较了遗传结构，并比较了保守性。蛋白质序列。系统发育分析表明，FtsZ1和FtsZ2序列在叶绿素和藻壳藻绿色藻谱系分裂之前可能分开，并且可能更早。遗传结构比较显示，内含子位置在FtsZ1和FtsZ2家族成员中是保守的，但在它们之间有所不同，这也支持早期分化。保守蛋白序列的比较表明了FtsZ1和FtsZ2家族成员不同的几个区域。这些保守的差异可能会定义FtsZ1和FtsZ2蛋白之间的功能差异。

著录项

  • 作者

    Stokes, Kevin David.;

  • 作者单位

    Michigan State University.;

  • 授予单位 Michigan State University.;
  • 学科 Biology Molecular.;Biology Plant Physiology.
  • 学位 Ph.D.
  • 年度 2003
  • 页码 254 p.
  • 总页数 254
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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