Determinants of Mating Type in Phytophthora

Judelson 9722947这项研究的目标是了解卵菌类真菌交配系统的调节和进化。以马铃薯晚疫病菌异交种为模式系统，通过克隆交配型基因座并确定其功能，确定交配型(有性亲和性)的基础。这有望导致对疫霉的其他异株和同株种的研究，对其他卵菌属交配型基因的研究，以及对参与交配反应的其他基因的研究。在本实验室以前的研究中，分离了交配型基因座两侧的DNA标记，并用来建立解释交配型基因决定的遗传模型；这些标记现在被用来通过使用粘粒和细菌人工染色体文库进行染色体行走来分离交配型基因座。此外，先前的研究表明，含有致病疫霉交配型决定因素的染色体区域表现出一些不寻常的遗传和生理特征。其中包括非孟德尔遗传模式，相当于在平衡致死基因座系统中观察到的遗传模式，以及区域的不稳定，其重新排列的倾向证明了这一点；这些现象将在本项目中继续得到解决。卵菌是一类重要但研究不足的二倍体低等真核生物，包括许多对经济和环境有重要意义的物种。包括植物和动物的病原体、其他病原体的生防剂和腐生植物。致病疫霉是这些研究的自然首选，这是因为该物种可用的成熟的分子和经典遗传技术。致病疫霉也是几种粮食作物广泛存在的一种极其重要的病原菌。因此，在这种病原体的分子操作方面发展专门知识的重要性怎么强调都不为过。此外，对致病疫霉交配型的分析为研究其生物学的一个重要方面提供了机会。交配系统是重要的，因为它们调节基因在种群中的流动；对于植物病原体，如致病疫霉，这类基因包括那些决定致病性、寄主偏好、小种特异性和杀菌剂抗性的基因。交配周期也很重要，因为有性孢子(卵孢子)寿命长，是植物病害暴发的重要接种源。从这些研究中将学到很多东西，包括二倍体交配型的调节和一个不寻常的染色体区域的进化。这项研究还将阐明卵菌生物学的基本方面，包括与基因调控、细胞通讯、信号转导和发育有关的方面。卵菌的交配很可能是由与子囊菌和担子菌完全不同的机制调控的，子囊菌和担子菌缺乏与卵菌的分类亲和力，交配受到不同的遗传和生化机制的控制。从长远来看，这些研究也可能具有重大的实际应用价值。如果能够确定控制交配的因素，就有可能通过操纵或利用交配周期的一部分来控制植物疾病。对致病疫霉的研究自然会导致对其他卵菌植物病原体的理解和最终控制。

Judelson 9722947 The goal of this research is to understand the regulation and evolution of mating systems in oomycete fungi. Using the heterothallic species Phytophthora infestans as a model system, the basis of mating type (sexual compatibility) will be determined by cloning the mating type locus and determining its function. This is expected to lead to studies of other heterothallic and homothallic species of Phytophthora, of mating type loci in other oomyceteous genera, and of other genes involved in the mating response. During previous studies by this laboratory DNA markers flanking the mating type locus were isolated and used to develop a genetic model to explain the determination of mating type; those markers are now being used to isolate the mating type locus by chromosome walking using cosmid and bacterial artificial chromosome libraries. In addition, the prior studies indicated that the chromosomal region containing the mating type determinants of P. infestans displayed several unusual genetic and physical characteristics. These included a non-Mendelian pattern of inheritance equivalent to that observed in systems of balanced lethal loci, and instability of the region as evidenced by its propensity to rearrange; these phenomena will continue to be addressed in this project. The oomycetes are an important but under-studied group of diploid lower eukaryotes that include many economically and environmentally significant species. These include pathogens of plants and animals, biocontrol agents of other pathogens, and saprophytes. P. infestans is a natural first choice for these studies due to the well-developed molecular and classical genetic techniques available for the species. P. infestans is also a widespread and enormously important pathogen of several food crops. Consequently, the importance of developing expertise in the molecular manipulation of this pathogen can not be over-stressed. Furthermore, the analysis of mating type in P. infestans represents an opportunity to study an important aspect of its biology. Mating systems are significant since they regulate the flow of genes through populations; for plant pathogens such as P. infestans, such genes include those determining pathogenicity, host preference, race specificity, and fungicide resistance. The mating cycle is also significant since the sexual spores (oospores) are long-lived and serve as an important source of inoculum for outbreaks of plant disease. Much will be learned from these studies including information about the regulation of mating type in diploids and the evolution of an unusual chromosomal region. This research will also illuminate fundamental aspects of oomycete biology, including those concerning gene regulation, cellular communication, signal transduction, and development. It is likely that mating in oomycetes is regulated by mechanisms very different from those of ascomycetes and basidiomycetes, which lack taxonomic affinity to the oomycetes and in which mating is controlled by different genetic and biochemical mechanisms. In the long term, these studies may have significant practical applications as well. If the factors which control mating can be identified, it might be possible to control plant diseases by manipulating or exploiting portions of the mating cycle. Studies in P. infestans will naturally lead to an understanding and ultimately control of other oomycete plant pathogens as well.