Role of DNA mismatch repair genes in meiotic recombination and gamete function

在最近的工作中，我们研究了模式植物拟南芥中三个关键的DNA修复基因的生物学作用。这项工作使我们能够将从酵母和小鼠中得出的一些结论扩展到植物，但更重要的是，它使我们能够揭示植物似乎独有的特征。在拟议的工作中，我们将首先检查所研究的基因是否对减数分裂重组产生类似的影响，因为我们已经证明了对有丝分裂重组。这是至关重要的，因为减数分裂重组是应用遗传学的关键角色（例如培育更好的品种）。其次，我们建议进行突变体筛选，以发现更多的基因限制植物中相似但不相同的序列之间的重组。这些新的突变体将相互测试，以确定它们代表多少不同的突变。此外，这些突变将被映射，以允许这些基因的最终克隆。最后，我们将探索我们研究的植物MutL同源物（AtMLH1和AtPMS1）的一个独特特征。当突变等位基因与野生型等位基因一起分离时，这两个基因的突变体对突变等位基因表现出明显的分离偏倚。这种现象在MutS同源物（AtMSH2）中未观察到，表明它不是简单地由缺乏MMR活性引起的。为了研究这种表型，我们将试图确定这种偏倚何时出现。此外，还将测试花粉萌发和花粉管生长。为了开始了解AtMLH 1在花粉发育或功能中所起的作用，我们将使用功能互补方法。细胞和阶段特异性启动子将用于确定需要AtMLH1蛋白的细胞类型或发育阶段。

In recent work we have investigated the biological roles of three key DNA repair genes in the model plant Arabidopsis. This work has allowed us to extend to plants some conclusions that had been drawn from work in yeast and mice, but more importantly, it has allowed us to uncover features that seem to be unique to plants. In the proposed work, we will first examine whether the genes under study exert a similar effect on meiotic recombination as we have shown on mitotic recombination. This is crucial as meiotic recombination is the key player in applied genetics (breeding better varieties for example). Secondly, we propose to perform a mutant screen in order to uncover additional genes limiting recombination between similar but non-identical sequences in plants. These novel mutants will be tested against each other to determine how many distinct mutations these represent. Furthermore, these mutations will be mapped to allow the eventual cloning of these genes. Lastly, we will explore a distinctive feature of the plant MutL homologues we have studied (AtMLH1 and AtPMS1). Mutants in both of these genes exhibit a marked segregation bias against the mutant allele when it is segregating alongside a wild-type allele. Such a phenomenon is not seen with a MutS homologue (AtMSH2) indicating that it does not simply result from the lack of MMR activity. To investigate this phenotype, we will try to determine when this bias arose. In addition, pollen germination and pollen tube growth will be tested. To begin to understand the role played by AtMLH1 in pollen development or function, we will use a functional complementation approach. Cell- and stage-specific promoters will be used to determine the cell type or developmental stage in or at which the AtMLH1 protein is required.