Control of Genome Structure

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The goal of the project is to elucidate mechanisms of genetic instability in Neurospora. Knowledge gained from the project should shed light on several general areas: recombination, mutation, and evolution. In addition, the project has practical significance for Neurospora geneticists and researchers working on related fungi (e.g. plant pathogens). During the grant period we will: 1) determine whether RIP is responsible for low- frequency inactivation of duplicate genes in vegetative tissue; 2) attempt to derepress RIP, by mutations, in vegetative cells for use in subsequent genetic and biochemical experiments; 3) isolate mutants deficient in RIP; 4) determine if an inverted linked duplication is subject to RIP, premeiotic reciprocal recombination, or both (to provide a test of the idea that high- frequency premeiotic deletion of sequences between linked duplications results from reciprocal recombination and to provide information for a potential approach to isolate RIP mutants); 5) determine if unlinked duplications are subject to recombination processes ("gene conversion" and reciprocal exchange) prior to meiosis; 6) identify the postulated DNA-cytosine deaminase involved in RIP; 7) investigate the resistance to RIP of rDNA, and the effect of RIP on the transposon Tad. Filamentous fungi have an unusual process, known as RIP, by which they inactive all but one copy of most genes present in more than one copy. This process was discovered by the Principal Investigator during a previous NSF award. The mechanism and significance of this process are unclear, and the PI hopes to learn more about them during this award. A better understanding of RIP will lead to more effective methods for genetic manipulation of industrially important fungi.