Microbial Genome Sequencing: Comparative Genomics of Telomeres in Pathogenic and Saprophytic Fungi

真核细胞的染色体是以简单DNA序列的重复为末端的线性分子。这些结构被称为端粒，防止DNA在复制过程中丢失，并防止不同染色体的融合。端粒在染色体行为、基因表达和基因组进化中也起着重要作用。在真菌和其他真核微生物中，端粒区域往往含有丰富的生态适应基因，而且往往高度可变，这提供了证据，表明它们受到生态位依赖的多样化选择的影响。尽管端粒序列很重要，但它们通常不会被用于高通量基因组测序的策略捕获，因此在基因组数据库中的代表性严重不足。在这个项目中，将使用有针对性的方法来分离和测定两种真菌的端粒区域：稻瘟病菌是一种非常重要的植物病原体；粗糙脉孢菌是一种腐生植物，其研究对生物学做出了深远的贡献。将对每个真菌物种的两个菌株进行检查，以彻底了解它们的端粒内容和组织；菌株之间的序列比较将揭示端粒变异的机制。这些信息将提高对真菌如何适应环境的理解，特别是对病原真菌如何避免宿主防御的理解。该项目产生的2.4兆碱基的高质量序列将对最终完成这些真菌的基因组序列至关重要。该项目将通过分子遗传学、高通量测序和生物信息学方面的本科生、研究生和博士后培训来提供教育。在该项目中产生的DNA文库和克隆将可供其他研究人员使用。组装和注释的序列将被发布到公共数据库，未完成的序列将通过以下网站访问：http://fungus.ceeb.uky.edu/cgibin/web-blast.cgi和http://www.riceblast.org.这是一个微生物基因组测序奖，通过国家科学基金会和农业部未来农业和食品系统倡议之间的合作活动提供资金。

Eukaryotic chromosomes are linear molecules that terminate in repeats of simple DNA sequences. These structures, called telomeres, guard against loss of DNA during replication and prevent fusion of different chromosomes. Telomeres also have important roles in chromosome behavior, gene expression and genome evolution. In fungi and other eukaryotic microbes, telomeric regions tend to be rich in genes for ecological adaptation and are often highly variable, providing evidence that they are subject to niche-dependent diversifying selection. Despite their importance, telomeric sequences usually are not captured using strategies employed for high-throughput genome sequencing and are, therefore, highly underrepresented in genome databases. In this project, targeted approaches will be used to isolate and sequence telomeric regions of two fungi: Magnaporthe grisea, a very important plant pathogen; and Neurospora crassa, a saprophyte whose study has made profound contributions to biology. Two strains of each fungal species will be examined to provide a thorough view of their telomere content and organization; and comparison of sequences between strains will reveal mechanisms of telomere variability. This information will improve understanding of how fungi adapt to their environment and, in particular, how pathogenic fungi avoid host defenses. The 2.4 megabases of high-quality sequence generated in this project will be essential for eventual completion of the genome sequences of these fungi. The project will provide education through undergraduate, graduate and postdoctoral training in molecular genetics, high-throughput sequencing, and bioinformatics. DNA libraries and clones generated in the project will be available to other researchers. Assembled and annotated sequences will be released to public databases and unfinished sequences will be accessible through the websites: http://fungus.ceeb.uky.edu/cgibin/web-blast.cgi and http://www.riceblast.org. This is a Microbial Genome Sequencing Award funded through a collaborative activity between the National Science Foundation and the Department of Agriculture Initiative for Future Agriculture and Food Systems.