One approach to understanding the genetic basis of traits is to study their pattern of inheritance among offspring of phenotypically different parents. Previously, such analysis has been limited by low mapping resolution, high labor costs, and large sample size requirements for detecting modest effects. Here, we present a novel approach to map trait loci using artificial selection. First, we generated populations of 10–100 million haploid and diploid segregants by crossing two budding yeast strains of different heat tolerance for up to 12 generations. We then subjected these large segregant pools to heat stress for up to 12 d, enriching for beneficial alleles. Finally, we sequenced total DNA from the pools before and during selection to measure the changes in parental allele frequency. We mapped 21 intervals with significant changes in genetic background in response to selection, which is several times more than found with traditional linkage methods. Nine of these regions contained two or fewer genes, yielding much higher resolution than previous genomic linkage studies. Multiple members of the RAS/cAMP signaling pathway were implicated, along with genes previously not annotated with heat stress response function. Surprisingly, at most selected loci, allele frequencies stopped changing before the end of the selection experiment, but alleles did not become fixed. Furthermore, we were able to detect the same set of trait loci in a population of diploid individuals with similar power and resolution, and observed primarily additive effects, similar to what is seen for complex trait genetics in other diploid organisms such as humans.

The genes YML070W/DAK1 andYFL053W/DAK2 in the yeast Saccharomyces cerevisiae were characterized by a combined genetic and biochemical approach that firmly functionally classified their encoded proteins as dihydroxyacetone kinases (DAKs), an enzyme present in most organisms. The kinetic properties of the two isoforms were similar, exhibiting K _{m (DHA)} of 22 and 5 μm and K _{m (ATP)} of 0.5 and 0.1 mm for Dak1p and Dak2p, respectively. We furthermore show that their substrate, dihydroxyacetone (DHA), is toxic to yeast cells and that the detoxification is dependent on functional DAK. The importance of DAK was clearly apparent for cells where both isogenes were deleted (dak1Δdak2Δ), since this strain was highly sensitive to DHA. In the opposite case, overexpression of either DAK1 or DAK2 made thedak1Δdak2Δ highly resistant to DHA. In fact, overexpression of either DAK provided cells with the capacity to grow efficiently on DHA as the only carbon and energy source, with a generation time of about 5 h. The DHA toxicity was shown to be strongly dependent on the carbon and energy source utilized, since glucose efficiently suppresses the lethality, whereas galactose or ethanol did so to a much lesser extent. However, this suppression was found not to be explained by differences in DHA uptake, since uptake kinetics revealed a simple diffusion mechanism with similar capacity independent of carbon source. Salt addition strongly aggravated the DHA toxicity, independent of carbon source. Furthermore, the DHA toxicity was not linked to the presence of oxygen or to the known harmful agents methylglyoxal and formaldehyde. It is proposed that detoxification of DHA may be a vital part of the physiological response during diverse stress conditions in many species.

Age is the highest risk factor known for a large number of maladies, including cancers. However, it is unclear how aging mechanistically predisposes the organism to such diseases and which gene products are the primary targets of the aging process. Recent studies suggest that peroxiredoxins, antioxidant enzymes preventing tumor development, are targets of age-related deterioration and that bolstering their activity (e.g., by caloric restriction) extends cellular life span. This review focuses on how the peroxiredoxin functions (i.e., as peroxidases, signal transducers, and molecular chaperones) fit with contemporary theories of aging and whether peroxiredoxins could be targeted therapeutically in the treatment of age-associated cancers.