<OL> <LI>Determine if differences in pathogenicity are associated with the presence of certain repetitive elements in Magnaporthe grisea;<LI> Characterize the evolution of the aflatoxin gene cluster in Aspergillus flavus;<LI>Characterize pathogenicity in Aspergillus flavus and the regulation of aflatoxin biosynthesis; <LI> Determine the conservation of the quinic acid gene cluster in Rhizoctonia solani.
Non-Technical Summary: Fungi represent the largest group of plant pathogens and throughout history have significantly limited the production of a safe and sustainable food supply. For example, late blight of potato, caused by Phytophthora infestans, resulted in the death of thousands of people and the emigration of millions from Ireland. The majority of serious plant epidemics in the US have been caused by non-indigenous pathogens. This threat of introduced pathogens is increasing due to a global trade, a highly mobile world population, and potential acts of bioterrorism. Rapid response to new pathogens requires accurate and reliable diagnostic procedures. This research is directed toward identifying regions of DNA diagnostic for pathogenicity, survival, and toxin production in fungi. Completion of the outlined research is necessary to locate specific DNA regions that can be used to identify individuals within a population and to distinguish between endemic and introduced fungal pathogens. <P> Approach: In order to develop rapid and reliable methods to detect pathogens, it is necessary to identify genes required for pathogenicity and toxin production, characterize their regulation, and understand their evolution. The fungi being examined limit the production of potato, maize, rice, and wheat. Magnaporthe grisea is widely recognized as a leading model for studying numerous aspects of host-pathogen interactions. Research will be directed at identifying pathogenicity genes based on differential gene expression, comparison with non-pathogens at the genus level, genes involved in secondary metabolism and recovery of genes from pathogenicity mutants. Aspergillus flavus is pathogenic on plants and animals and also produces the carcinogen, aflatoxin. Whole genome Affymetrix GeneChip DNA arrays will be used in comparative genome hybridization studies to examine differences between A. flavus and A. oryzae, a closely related non-pathogenic species that does not produce aflatoxin. The goal of these studies is to identifying genes required for pathogenicity and aflatoxin production in A. flavus. The synthesis of aflatoxin will be used as a model to better understand gene function and evolution. To do this, we will identify nucleotide sequence variation within coding and non-coding portions of the aflatoxin gene cluster in population samples of A. flavus and A. parasiticus. Finally, we propose to examine the quinic acid gene cluster in Rhizoctonia solani to better understand how the down regulation of the shikimic acid pathway associated with dsRNAs contributes to virulence in R. solani.