Dissertation Research: Fitness Consequences and Evolution of R-gene Mediated Resistance

植物中的R基因决定个体是否对引起疾病的病原体的特定菌株具有抗性或易感性。R基因在自然植物种群中往往是相当可变的，但维持这种遗传变异的力量还没有得到很好的理解。一种假设是，在某些环境条件下，易感植物比抗性植物产生更多的种子。以这种方式，抗性并不总是有利的，并且两种表型都得以维持。本研究中详细描述的实验验证了一个假设，即在某些情况下，对病原体产生抗性反应的能量成本大于植物从阻止病原体生长中获得的益处。如果R基因抗性反应成本高昂，那么抗性反应的水平可能决定抗性反应是否具有净效益或成本。此外，本项目还将调查不同水平的抗性反应对植物是否有不同的利益和成本。本研究将探讨在温室中以其自然病原霜霉病菌侵染拟南芥。 将比较因存在/不存在R基因而不同但在其他方面遗传上相同的植物。结合理论研究，本实验将探索R基因介导的抗病水平是否是影响拟南芥与霜霉病菌共进化相互作用的重要因素，为植物-病原菌共进化相互作用研究提供基础知识。 了解自然种群中的这些相互作用将提高农业植物物种病原体抗性的应用。

Bergelson9972708R-genes in plants determine whether individuals are resistant or susceptible to particular strains of disease causing pathogens. R-genes tend to be quite variable in natural plant populations, yet the forces maintaining this genetic variation are not well understood. One hypothesis is that susceptible plants produce more seed than resistant plants under certain environmental conditions. In this way, resistance is not always favored and both phenotypes are maintained. The experiments detailed in this research test the hypothesis that the energetic cost of having a resistance response to a pathogen is greater than the benefit the plant receives from stopping pathogen growth under some circumstances. If R-gene resistance responses are costly, then the level of resistance response may determine whether a resistance response has a net benefit or cost. In addition, this project will investigate whether different levels of resistance response have different benefits and costs for the plants. Arabidopsis thaliana infected in the greenhouse with its natural pathogen, downy mildew, will be investigated. Plants that differ by the presence/absence of an R-gene but are otherwise genetically identical will be compared. In combination with theoretical investigations, these experiments will explore whether the level of R-gene mediated resistance is an important factor in the coevolutionary interactions between A.thaliana and downy mildew.These experiments will provide fundamental knowledge about plant-pathogen coevolutionary interactions. Knowledge about these interactions in natural populations will improve the application of pathogen resistance in agricultural plant species.