THE GOAL OF OUR FIRST NASA-EXOBIOLOGY GRANT WAS TO STUDY SPECIATION BY CREATING DE NOVO YEAST SPECIES THEN DETERMINING WHAT GENOMIC CHANGES OCCURRED FOLLOWING THE "SHOCK" OF INTERSPECIFIC HYBRIDIZATION. OUR SUCCESSOR TO THAT AWARD FOLLOWS UP ON OUR MOST RECENTLY PUBLISHED WORK WHERE WE REPORT ON AN UNEXPECTED TWIST IN THE DRAMA OF ADAPTATION AND SPECIATION: THE POSSIBILITY THAT SEVERE STRESS SPECIFICALLY ELEVATES RATES OF GENOMIC REARRANGEMENT CREATING NEW VARIANTS SOME OF WHICH ARE ADAPTIVELY FAVORED AND WHOSE NOVEL GENOME STRUCTURES FAVOR REPRODUCTIVE ISOLATION IN SYMPATRY. WE WILL INVESTIGATE THISPOSSIBILITY BY PURSUING THREE OBJECTIVES. FIRST WE WILL IDENTIFY ISOLATE AND ASSAY THE FITNESS EFFECTS OF SPECIFIC LARGE-SCALE GENOMIC REARRANGEMENTS THAT ARISE IN YEAST DURING PROLONGED STARVATION. SECOND WE WILL DETERMINE THE FREQUENCY WITH WHICH THESE GENOMIC REARRANGEMENTS ARISE IN STARVED CULTURES. THIRD WE WILL DELINEATE THE GENETIC PATHWAYS WHICH LEAD TO STARVATION-INDUCED GENOMIC REARRANGEMENT BY SYSTEMATICALLY EVALUATING GENES INVOLVED IN HOMOLOGOUS RECOMBINATION NONHOMOLOGOUS END-JOINING MISMATCH REPAIR ENVIRONMENTAL SIGNAL TRANSDUCTION AND RETROTRANSPOSITION. ACHIEVING THESE OBJECTIVES WILL FUNDAMENTALLY ADVANCE OUR UNDERSTANDING OF THE FEEDBACK BETWEEN GENOMES AND THEIR EXTERNAL ENVIRONMENT. KNOWING HOW STARVING CELLS UNDERGO GENOMIC CHANGES THAT MAKE THEM STRESS-RESISTANT AND KNOWING THE COST OF SUCH MUTATIONS WILL BETTER ENABLE US TO PREDICT UNDER WHAT GENETIC AND ENVIRONMENTAL CONDITIONS STRESS-INDUCED GENOME REARRANGEMENTS ARE LIKELY TO BE LOST TO DRIFT SELECTION OR SEXUAL RECOMBINATION OR TO BE RETAINED IN A REPRODUCTIVELY ISOLATED SUBPOPULATION THAT BECOMES A NEW SPECIES.

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