EVOLUTIONARY GENETICS OF R LOCI IN ARABIDOPSIS

以.在拟南芥中，R基因座的等位基因通过与 细菌或真菌特异性无毒（AVR）基因依赖性产物 病原体 在分子生物学和 R基因的功能表征提供了及时的机会， 研究的生态或分子群体遗传学 在这个物种的抵抗力：基本上没有什么是已知的 R基因位点的多态性程度、等位基因的年龄或 多态性的地理分布 我们建议调查 为什么许多R基因位点对两个或多个功能等位基因是多态的 通过利用两种互补的方法来研究选择作用， 在抗性基因座上。 首先，我们将进行统计分析， DNA序列多态性在种群（和物种）内和种群（和物种）之间 5个R基因座和沿着2条染色体。 第二，我们将通过实验 估计抗性和敏感等位基因的相对适合度， 通过构建转基因株系和对照株系， 一个thaliana。总之，这些研究将使我们能够测试特定的 保持多态性和进化的选择模型 R基因在A. thaliana，and will allow允许us to make推论about 这些寄主-病原体时空种群动态 交互. 我们的数据将使我们能够验证人们普遍认为 R等位基因的快速选择性更替， 病原体和宿主之间的进化军备竞赛 我们还将 等位基因长期进化维持证据试验 在R基因座的变异，一个理论的亚类作出的预测， 基因对基因的协同进化模型这些测试需要以下信息： 多态性的背景级别，我们将通过 系统性调查沿沿着两条染色体核苷酸多态性 A. thaliana.关于人口贩运的程度和空间格局的资料 分子遗传变异是测试历史 在R基因座选择的证据，并将有助于建立拟南芥作为 一个丰富的植物分子进化研究的模式系统 性状

In A. thaliana, alleles of R loci confer resistance by interacting with specific avirulence (avr) gene-dependent products of bacterial or fungal pathogens. The rapid progress being made in the molecular and functional characterization of R genes provides a timely opportunity to investigate the ecological or molecular population genetics of resistance in this species: essentially nothing is known about the extent of polymorphism at R gene loci, the age of alleles, or the geographical distribution of polymorphism. We propose to investigate why many R gene loci are polymorphic for two or more functional alleles by utilizing two complementary approaches for studying selection acting on resistance loci. First, we will perform a statistical analysis of DNA sequence polymorphism within and among populations (and species) at five R loci and along two chromosomes. Second, we will experimentally estimate the relative fitness of resistant and susceptible alleles at two loci, Rpm1 and Rps5, by constructing transgenic and control lines of A thaliana. Together, these studies will allow us to test specific selection models for the maintenance of polymorphism and the evolution of R genes in A. thaliana, and will allow us to make inferences about the spatio-temporal population dynamics of these host-pathogen interactions. Our data will enable us to test the widespread belief that there will be a rapid selective turnover of R alleles resulting from an evolutionary arms race between pathogen and host. We will also test for evidence of long-term evolutionary maintenance of allelic variation at R loci, a prediction made by a subclass of theoretical models of gene-for-gene coevolution. These tests require information on background levels of polymorphism, which we will generate through a systematic survey of nucleotide polymorphisms along two chromosomes of A. thaliana. Information on the extent and spatial patterning of molecular genetic variation is integral to testing for historical evidence of selection at R loci, and will help establish Arabidopsis as a model system for molecular evolutionary studies on a wealth of plant traits.