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

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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.