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

伯格森9972708R-植物中的基因决定了个体是否对引起病原体的特定菌株具有抵抗力或易感性。在自然植物种群中，R基因往往是非常不同的，然而维持这种遗传变异的力量还没有被很好地理解。一种假设是，在某些环境条件下，敏感植物比抗性植物产生更多的种子。这样，抗性并不总是被看好，两种表型都保持不变。这项研究中详细介绍的实验验证了这样一种假设，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好处。如果R基因抗性反应是昂贵的，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，该项目将调查不同水平的抗性反应是否对植物有不同的收益和成本。在温室内感染拟南芥的自然病原菌霜霉病将被调查。由于存在/不存在R基因而不同，但在其他方面基因相同的植物将被比较。结合理论研究，这些实验将探索R基因介导的抗性水平是否是拟南芥与霜霉病共同进化相互作用的重要因素，这些实验将为植物-病原菌共同进化相互作用提供基础知识。对自然种群中这些相互作用的了解将促进在农业植物物种中应用病原菌抗性。

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.