Host jump enabling factors in a fungal/grass pathosystem

黑穗病真菌是主要感染禾本科植物的活体营养型病原体，其中包括重要的谷类作物植物如大麦、小麦、玉米、高粱、甘蔗和牧草。目前已鉴定的1200种黑穗病真菌具有较强的寄主特异性，可侵染4000多种植物。病原体的宿主范围可能是获得新的或适应的毒力因子（如小的分泌蛋白，所谓的效应物）或/和无毒力因子（avr基因）丧失的产物。在宿主方面，缺乏限制性分子，例如会导致严格防御反应的特定R基因或总之会导致抗性的数量性状，可以限制病原体的宿主范围。我们确定了黑粉菌bromivora和不同的其他草感染，但不是短柄草感染黑穗病，能够引起感染症状和完全完成其生命周期的模式草短柄草二穗草杂交种之间的种间交配对。这一发现是通过采用遗传回交方法辅助比较基因组方法来剖析宿主跳跃使能因子的示例性分子基础的基础。宿主跳变事件在过去造成了严重的损害，在未来也将是对作物的持续威胁。除了它们在经济上的重要性，对分子基础的理解也会影响我们对1200种甚至更远的黑鲈进化方面的看法。

Smut fungi are biotrophic pathogens which infect mainly grasses, among them important cereal crop plants like barley, wheat, corn, sorghum, sugarcane and forage grasses. The so far 1200 smut fungi species identified show relatively strict host specificity and can infect in sum up to 4000 different plant species. The host range of a pathogen is likely a product of the acquisition of novel or adapted virulence factors (like small secreted proteins, so called effectors) or/and loss of avirulence factors (avr-Genes). On the host side the lack of restricting molecules like for example specific R-genes that would lead to strict defense responses or quantitative traits that in sum would lead to resistance can limit the host range of the pathogen. We identified interspecific mate pairs between Ustilago bromivora and different other grass-infecting but not Brachypodium infecting smuts which are able to cause infection symptoms and full completion of their lifecycle as hybrids on the model grass Brachypodium distachyon..This finding is the basis to dissect exemplary the molecular basis of host jump enabling factors by the employment of a genetic backcross approach assisted with comparative genomic approaches. Host jump events caused severe damage in the past and will also be in the future a constant threat to crops. Beside their economic importance an understanding of the molecular basis will have also impact on our view on evolutionary aspects of the ~1200 smuts and maybe beyond.