EVOLUTIONARY GENETICS OF R LOCI IN ARABIDOPSIS

在拟南星天牛中，R基因座的等位基因通过与 细菌或真菌的特异性无毒(AVR)基因依赖产物 病原体。在分子和生物科学领域取得的快速进展 R基因的功能特征提供了一个及时的机会 调查生态或分子群体遗传学 该物种的抗药性：基本上对该物种的 R基因座的多态程度、等位基因的年龄或 多态的地理分布。我们建议调查 为什么许多R基因座位对两个或更多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行为 在抗性基因上。首先，我们将进行统计分析， DNA序列在种群(和物种)内和之间的多态性 5个R基因座，沿2条染色体。第二，我们将在实验中 估计抗性和敏感等位基因的相对适合度 两个基因座Rpm1和Rps5的构建 塔里亚纳。总之，这些研究将使我们能够测试特定的 维持多态和进化的选择模型 这将使我们能够推断出 这些寄主病原菌的时空种群动态 互动。我们的数据将使我们能够检验人们普遍认为的 会导致R等位基因的快速选择性更替 来自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的检验 R基因座的变异，这是由理论中的一个子类做出的预测 基因对基因共同进化的模型。这些测试需要以下信息 多态的背景级别，我们将通过 日本血吸虫两条染色体核苷酸多态性的系统调查 塔里亚纳(A.thaliana)关于范围和空间格局的信息 分子遗传变异是历史检验不可或缺的一部分 R基因座的选择证据，并将有助于将拟南芥建立为 丰富植物分子进化研究的模式系统 特征。

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.