Role of yeast-mycelium transition in the pathogenicity of the Dutch elm disease fungus Ophiostoma novo-ulmi

荷兰榆树病（Dutch elm disease， DED）是榆树最具破坏性的病害。据估计，在过去的100年里，超过10亿棵成熟的榆树被两次连续的由两种称为Ophiostoma ulmi和O. novoo -ulmi的微观真菌引起的DED大流行杀死。我们正在进行的研究表明，一个编码高亲和力铵转运体的蛇孔基因（称为Omp2）对DED病原体对榆树的毒力很重要。我们打算阐明Omp2在发病机制中的作用。特别是，我们将验证Omp2的作用源于其在低浓度铵存在下对DED真菌的酵母和菌丝体形式的调节作用的假设。我们进一步建议分析另外两个可能参与真菌生长其他调控途径的基因，正如酵母或菌丝发育受损的O. novo-ulmi突变体的恢复所表明的那样。该项目的短期效益是更好地了解DED真菌如何在榆树中发展并最终杀死它们。预期的长期效益是确定真菌目标，以开发有效和环境可接受的控制方法来拯救榆树。

Dutch elm disease (DED) is the most destructive disease of elms. It has been estimated that, during the last 100 years, over one billion mature elms were killed by two successive pandemics of DED caused by two microscopic fungi called Ophiostoma ulmi and O. novo-ulmi. Our ongoing research suggests that an Ophiostoma gene (called Omp2) coding for a high affinity ammonium transporter is important for the virulence of the DED pathogens towards elms. We intend to clarify the role of Omp2 in pathogenesis. In particular, we will verify the hypothesis that the action of Omp2 stems from its effect on the regulation of yeast and mycelium forms of the DED fungi in the presence of low concentrations of ammonium. We further propose to analyse two additional genes which may be involved in other regulatory pathways for fungal growth, as suggested by the recovery of O. novo-ulmi mutants with impaired yeast or mycelial development. The short-term benefit of this project is a better understanding of how the DED fungi develop in elms and eventually kill them. Anticipated long-term benefits are the identification of fungal targets for the development of efficient and environmentally acceptable control methods to save the elms.