Maintenance of plastid genome stability in plants

光合作用是地球上最重要的生物过程之一。我们所有的食物以及我们对纤维和建筑材料的大部分需求都直接或间接地由这个过程提供。光合作用发生在叶绿体中，并且依赖于位于该细胞器和细胞核中的基因子集。叶绿体中存在的基因是质体基因组的一部分，编码参与光合作用、基因转录和蛋白质合成的RNA和蛋白质。尽管这种基因组对植物和一般生命至关重要，但我们对其转录，复制和DNA修复机制知之甚少。近年来，我的实验室已经表征了一个小家族的植物特异性DNA结合蛋白，称为Whirly，以及一个专门的I型聚合酶，PolIB，参与维持质体基因组的稳定性。 在下一个授予期，我们建议继续我们的表征机制，有助于保持质体基因组的稳定性。我们将把我们的注意力主要集中在几个基因的突变导致超敏反应的细胞器特异性DNA双链断裂诱导剂环丙沙星。这些基因编码WHY1和WHY3蛋白、质体Sigma因子SIG6、重组酶RecA1、PolIB DNA聚合酶和RecG功能同源物DRT 111。我们将确定这些基因之间的遗传相互作用，这将为理解维持质体基因组稳定性的机制提供重要线索。由于初步结果表明，转录调节因子SIG6作为基因组稳定性的一个重要介质，我们将测试的假设，转录有一个强大的基因组不稳定的影响，质体在早期的发展阶段和Whirly蛋白有助于抵消这种影响。

Photosynthesis is one of the most important biological processes on earth. All our food and a large part of our needs for fibre and building materials are provided by this process, either directly or indirectly. Photosynthesis occurs in the chloroplast, and depends on a subset of genes that are located in this organelle and in the nucleus. The genes present in the chloroplast are part of the plastid genome and encode for RNA and proteins involved in photosynthesis, gene transcription and protein synthesis. Despite the crucial importance of this genome for plants and life in general, we still know very little about its transcription, replication and DNA repair mechanisms. In recent years my laboratory has characterized a small family of plant specific DNA-binding proteins, called Whirly, as well as a specialized type-I polymerase, PolIB, that are involved in the maintenance of plastid genome stability. In the next granting period we propose to continue our characterization of the mechanisms that contribute to maintain the stability of the plastid genome. We will focus our attention mostly on a few genes whose mutation leads to hypersensitivity to the organelle-specific DNA double-stranded breaks inducing agent ciprofloxacin. These genes code for the WHY1 and WHY3 proteins, the plastid Sigma factor SIG6, the recombinase RecA1, the PolIB DNA polymerase and the RecG functional homolog DRT111. We will determine the genetic interactions between these genes, which should provide important clues to understand the mechanisms that maintain plastid genome stability. As preliminary results indicate that the transcription regulator SIG6 acts as an important mediator of genome stability, we will test the hypothesis that transcription has a strong genome destabilization effect in plastids at an early stage of development and that Whirly proteins contribute to counteract this effect.