DISEASE ON NEW HOSTS: MICROBOTRYUM AS A MODEL SYSTEM

病原体从动物物种的宿主转移导致了人类感染疾病的数量不断增加。对宿主转移的研究主要是通过追踪疫情来源和确定宿主宿主的历史方法进行的。虽然这是预防疾病传播的一个重要组成部分，但拟议研究的目标是开发一种更具预测性的方法来研究宿主转移，并对所涉及的生态和遗传过程有一个基本的了解。拟议的研究将把系统发育数据分析与实验微进化研究结合起来，以实现这些目标。系统发育分析将被用来确定过去有利于宿主转移的宿主和病原体的特征，并利用这些特征来预测未来宿主转移的可能性。然后将使用接种实验来验证这些预测。将对现有种群发生寄主转移的遗传和生态学基础以及新出现的病原体的进化和种群动态进行研究。将以真菌病原菌Microbotryum作为模式系统。这种病原菌具有大量自然产生的寄主小种的特点，很容易被操纵，而且进行大规模的实验研究是可行的。这一广泛研究的天然植物病原体系统已经为性传播疾病的生物学提供了有价值的见解。这项建议将针对这些特定的目标：1.利用系统发育信息预测寄主转移；2.在种群动态的背景下研究寄主转移，从而确定新寄主上病原体的种群动态，b.确定遗传因素在病原体向新寄主传播中的作用，c.确定病原体专化在新寄主持久性中的作用。

Host shifts of pathogens from animal species have lead to an increasing number of infectious diseases in humans. Studies of host shifts have been conducted primarily through the historical approach of tracing the epidemic's origin and identifying the reservoir host. While this is an important component of preventing disease transmission, the goals of the proposed research are to develop a more predictive approach to the study of host shifts and to attain a basic understanding of the ecological and genetic processes involved. The proposed research will combine phylogenetic data analysis with experimental microevolutionary studies to achieve these goals. The phylogenetic analyses will be used to determine the characteristics of hosts and pathogens that have favored host shifts in the past, and to use these characteristics to make predictions about the likelihood of future host shifts. Inoculation experiments will then be used to test these predictions. Studies will be carried out on the genetic and ecological basis of host shifts occurring in present day populations, and on the evolutionary and population dynamics of newly emerged pathogens. The fungal pathogen Microbotryum will be used as a model system. This pathogen is characterized by a large number of naturally occurring host-races, it is easily manipulated, and large experimental studies are feasible. This extensively studied natural plant pathogen system has already provided valuable insights into the biology of sexually transmitted diseases. This proposal will address these specific aims: 1. To use phylogenetic information to predict host shifts; and 2. To study host shifts in a population dynamic context, and thereby, a. Determine the population dynamics of pathogens on new hosts, b. Determine the role of genetic factors in the transmission of a pathogen to a new host, c. Determine the role of pathogen specialization in persistence on new hosts.