Evolutionary Genetics of R Loci in Arabidopsis

拟南芥 R 基因座的进化遗传学

• 批准号: 7074572
• 负责人: JOY M BERGELSON
• 金额: $ 31.96万
• 依托单位: UNIVERSITY OF CHICAGO
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-07-01 至 2008-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7074572
• 关键词: Arabidopsis; alleles; biochemical evolution; functional /structural genomics; gene expression; genetic models; genetic polymorphism; genetically modified plants; immunogenetics; model design /development; natural selections; plant population genetics; plant proteins; single nucleotide polymorphism

DESCRIPTION (provided by applicant): Plant defense against pathogens is induced by R-genes, a large multigene family of signal transducing proteins. Approximately a dozen R-genes have been shown to be segregating for both resistance and susceptibility alleles, and several of these are known to harbor ancient polymorphisms. R-genes can also show evidence of rapid, adaptive evolution, presumably as a consequence of coevolutionary interactions with pathogens. That both of these evolutionary processes -balancing selection and adaptive evolution -occur in the same gene is remarkable, and requires explanation. The general aims of this proposal are to elucidate the mechanisms of natural selection acting on segregating R-gene alleles and to determine the physiological basis for their fitness differences. We believe that both these pursuits are necessary to fully understand the evolutionary genetics of disease resistance variation. Sequence variation at three complex loci containing a variable number of R-gene repeats will also be investigated. We hypothesize that complex loci evolve in response to strong balancing selection and large costs of specific resistance alleles. The data will allow us to evaluate alternative hypotheses, and potentially to unite simple and complex R-gene loci under a single model of selection. Our specific aims in this grant period will be to (1) Test the hypothesis that a large cost of resistance is characteristic of long-lived polymorphisms between resistance and null susceptibility alleles; (2) Test the prediction that this cost is lower for alleles that participate in a stable polymorphism between functional alternatives; (3) Analyze the cost of Rpml resistance by characterizing R and S lines in terms of gene expression, biochemical intermediates and biochemical end products; (4) Test the role of particular defense responses in generating the cost of Rpml resistance; (5) Characterize and contrast nucleotide polymorphism of single-copy R-gene loci in a reference set of 96 A. thaliana accessions, and of tandem arrays in a subset of these samples, to identify the spectrum of evolved responses by R-genes to disease; and (6) Develop population genetic models of the major modes of R-gene polymorphism.

描述（由申请人提供）：植物对病原体的防御是由 R 基因诱导的，R 基因是信号转导蛋白的大型多基因家族。大约有十几个 R 基因已被证明可分离抗性和易感性等位基因，其中一些已知具有古老的多态性。 R基因还可以显示快速、适应性进化的证据，这可能是与病原体共同进化相互作用的结果。这两个进化过程——平衡选择和适应性进化——发生在同一个基因中，这是值得注意的，需要解释。该提案的总体目标是阐明自然选择作用于分离 R 基因等位基因的机制，并确定其适应度差异的生理基础。我们相信，这两种追求对于充分理解抗病性变异的进化遗传学都是必要的。还将研究包含可变数量 R 基因重复的三个复杂基因座的序列变异。我们假设复杂基因座的进化是为了响应强平衡选择和特定抗性等位基因的巨大成本。 这些数据将使我们能够评估替代假设，并有可能在单一选择模型下将简单和复杂的 R 基因位点结合起来。我们在此资助期内的具体目标将是（1）检验以下假设：耐药性和无效易感性等位基因之间的长寿命多态性的特征是耐药性的巨大成本； (2) 测试对于参与功能替代之间稳定多态性的等位基因来说该成本较低的预测； (3)通过对R和S系的基因表达、生化中间产物和生化终产物进行表征，分析Rpml抗性的成本； (4)测试特定防御反应在产生Rpml抵抗成本中的作用； (5) 表征和对比 96 个拟南芥种质参考集中的单拷贝 R 基因位点的核苷酸多态性，以及这些样品子集中的串联阵列的核苷酸多态性，以确定 R 基因对疾病的进化反应谱； (6)建立R基因多态性主要模式的群体遗传模型。