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Identification et caracterisation de facteurs impliques dans la replication et la stabilite des genomes des organelles de plantes.

机译：鉴定和表征涉及植物细胞器基因组复制和稳定性的因素。

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摘要

Compared to the nuclear genome, very little is known about the genomes of the two plant cytoplasmic organelles, the plastid and the mitochondria. Indeed, very few factors involved in either the replication or the repair of these genomes have been identified. Here we show the implication of the Whirly protein family in the maintenance of organellar DNA. Indeed, mutations in Whirly genes lead to DNA rearrangements in both Arabidopsis thaliana and Zea mays plastids. These rearrangements are the product of microhomology-mediated break-induced replication that rarely occurs in wild-type plants but increases in absence of Whirly proteins. In a mutant plant devoid of plastidial Whirly proteins, these new DNA molecules can be amplified up to fifty times the normal DNA level and cause a variegated phenotype.;In the course of the study of the Whirly mutant plants, we developed a strategy, based on the use of the antibiotic ciprofloxacin, to induce DNA double-strand breaks specifically in plant organelles. The Arabidopsis mutant plants without Whirly proteins in the plastids are more sensitive to the antibiotic ciprofloxacin than wild-type plants. Accordingly, there is a much larger increase in the number of rearranged DNA molecules in the plastids of the mutant plants than in the control plants. Surprisingly, while the mutant plants devoid of Whirly proteins in the mitochondria do not show increased sensitivity to the drug, they do accumulate more rearrangements in their mitochondrial DNA compared to wild-type plants. These results suggest that the Whirly proteins are involved in the repair of DNA double-strand breaks in the plant organelle genomes.;Our study of the plant organelle genome stability has lead us to a family of proteins homologous to the DNA polymerase I in bacteria. This family has been proposed to be responsible for most of the DNA-synthesis activity in the plant organelles. We bring genetic proof to support this hypothesis using mutants of the two PolI genes of Arabidopsis. The combined mutation of both genes is lethal and the single mutations cause a decrease in the relative DNA levels in the organelles, thus confirming the involvement of both genes in DNA replication. Interestingly, mutants of the PolIB but not PolIA gene shows increase sensitivity to ciprofloxacin suggesting a function in DNA repair. In line with these results, a cross between a PolIB mutant and the mutant of plastid Whirly genes resulted in plants with severe growth defects and numerous rearrangements in the plastid DNA. In conclusion, we have identified two factors involved in the metabolism of organelle DNA and proposed a simple model of how these genomes are maintained in the plant cell.;Keywords : Plant biology, maintenance of the genome, DNA replication, DNA repair, plastid, mitochondria, Whirly proteins, DNA polymerase.
机译：与核基因组相比，对两种植物细胞质细胞器（质体和线粒体）的基因组知之甚少。实际上，已经鉴定出很少涉及这些基因组的复制或修复的因素。在这里，我们显示了Whirly蛋白家族在维持细胞器DNA中的意义。实际上，Whirly基因的突变会导致拟南芥和玉米质体中的DNA重排。这些重排是由微同源性介导的断裂诱导的复制的产物，这种复制在野生型植物中很少发生，但是在缺乏Whirly蛋白的情况下会增加。在没有质体Whirly蛋白的突变植物中，这些新的DNA分子可以扩增到正常DNA水平的50倍，并产生多样化的表型。在研究Whirly突变植物的过程中，我们基于在使用环丙沙星抗生素时，特别是在植物细胞器中诱导DNA双链断裂。质体中不含Whirly蛋白的拟南芥突变植物比野生型植物对抗生素环丙沙星更敏感。因此，与对照植物相比，突变植物的质体中重排的DNA分子的数量大大增加。令人惊讶的是，虽然线粒体中不含Whirly蛋白的突变植物对药物的敏感性并未提高，但与野生型植物相比，它们的线粒体DNA确实积累了更多的重排。这些结果表明，Whirly蛋白参与了植物细胞器基因组DNA双链断裂的修复。我们对植物细胞器基因组稳定性的研究使我们获得了与细菌中DNA聚合酶I同源的蛋白质家族。已经提出该家族负责植物细胞器中的大多数DNA合成活性。我们利用拟南芥的两个PolI基因的突变体，提供了遗传证据来支持这一假设。这两个基因的组合突变是致死性的，单个突变导致细胞器中相对DNA水平的降低，从而证实了这两个基因都参与了DNA复制。有趣的是，PolIB的突变体而不是PolIA基因的突变体显示出对环丙沙星的敏感性增加，表明在DNA修复中起作用。与这些结果一致，PolIB突变体和质体Whirly基因的突变体之间的杂交导致植物具有严重的生长缺陷和质体DNA中的许多重排。总而言之，我们确定了细胞器DNA代谢的两个因素，并提出了一个简单的模型来说明如何在植物细胞中维持这些基因组。关键词：植物生物学，基因组维护，DNA复制，DNA修复，质体，线粒体，Whirly蛋白，DNA聚合酶。

著录项

  • 作者

    Parent, Jean-Sebastien.;

  • 作者单位

    Universite de Montreal (Canada).;

  • 授予单位 Universite de Montreal (Canada).;
  • 学科 Biology Molecular.
  • 学位 Ph.D.
  • 年度 2011
  • 页码 268 p.
  • 总页数 268
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 肿瘤学;
  • 关键词

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