Determinants of mating type in the oomycete, Phytophthora infestans

9405179决定致病疫霉A1和A2交配型(性亲和型)的Judelson基因座将通过基于地图的(位置)克隆技术进行遗传特征分析和分离。致病疫霉是一种破坏性的植物病原体，也是卵菌的一个很好的实验系统。卵菌是一类重要的二倍体低等真核生物，包括许多具有重要经济意义的动植物病原体。在初步研究中，分离了与A1和A2基因座连锁的多态DNA标记，并分析了它们在三个杂交组合中的分离模式。这些结果表明，交配类型是由决定A1和A2类型的单基因座决定的。交配型区域以一种新的模式分离，这让人想起平衡致死，因为在存活的后代中只观察到四种可能的基因类型中的两种。这种非孟德尔现象可能会解决卵菌类真菌交配类型确定的一个复杂问题，因为卵菌类真菌是二倍体，它从继承了双亲等位基因的后代中消除了不明确的基因类型。此外，使用DNA标记的长距离限制性图谱表明，到目前为止，包含交配型基因座的区域已经缩小到90kb。在本研究中，在完成包含交配型决定因素的区域的遗传和物理特征后，将通过染色体行走来分离交配型基因座。互补分析，使用我为致病疫霉开发的可靠的转化程序，最终将证明这些基因座已经被克隆。此外，将分离在交配过程中调节的基因，以便将来剖析交配过程的调节。这个项目的主题是分析致病疫霉的交配型，这是研究卵菌生物学的一个重要方面的机会。由卵菌引起的植物病害分布广泛、破坏性强、防治难度大。因此，开发操纵卵菌的专业知识的重要性怎么强调都不为过。从长远来看，这些研究可能会有重大的实际应用。如果能够确定控制交配的因素，就有可能通过工程植物防御来对交配激素做出反应，或者通过刺激交配周期有效地阻止异源物种的病原生长来控制由卵菌引起的植物病害。这些研究还可能导致人口研究的诊断标记，这是评估疾病控制战略所必需的。对致病疫霉的研究自然也会导致对其他卵菌的了解。***

9405179 Judelson Loci determing the A1 and A2 mating types (sexual compatibility types) of the oomycete, Phytophthora infestans, will be genetically characterized and isolated by mapbased (positional) cloning techniques. P. infestans is a destructive plant pathogen and a good experimental system within the oomycetes, an important but little-studied group of diploid lower eukaryotes that include many economically significant pathogens of plants and animals. In preliminary studies, polymorphic DNA markers linked to the A1 and A2 loci were isolated and their pattern of segregation analyzed in three crosses. Those results suggest that mating type is determined by single loci determining the A1 and A2 types. The mating type regions segregate in a novel pattern reminiscent of balanced lethals, as only two of the four possible genotypes are observed in viable progeny. This non-Mendelian phenomenon may possibly address one of the complications of determining mating type in oomycete fungi, which are diploids, by eliminating ambiguous genotypes from progeny inheriting alleles from both parents. Also, long-range restriction mapping using the DNA markers suggests that the region containing the mating type loci has been narrowed so far to a 90 kb region. In the present study, after completing the genetic and physical characterization of the regions containing the mating type determinants, the mating type loci will be isolated by chromosome walking. Complementation assays, using reliable transformation procedures that I have developed for P. infestans, will ultimately prove that the loci have been cloned. In addition, genes regulated during mating will be isolated to enable the future dissection of the regulation of the mating process. %%% The subject of this project, the analysis of mating type in the fungus Phytophthora infestans, represents an opportunity to study an important aspect of the biology of the oomycetes. The plant diseases caused by oomycetes are widespread, highly destructive, a nd very difficult to control. Therefore, the importance of developing expertise in manipulating oomycetes can not be overstressed. In the long term, these studies may have significant practical applications. If the factors which control mating can be identified, it might be possible to control plant diseases caused by oomycetes by engineering plant defenses to respond to the mating hormones, or by stimulating the mating cycle which effectively turns off pathogenic growth in heterothallic species. These studies may also lead to diagnostic markers for population studies necessary to assess strategies for controlling disease. Studies in P. infestans will naturally lead to an understanding of other oomycetes as well. ***