The PSO3 gene is involved in error-prone intragenic recombinational DNA repair in Saccharomyces cerevisiae

Summary The induction of gene conversion and mitotic crossing-over by photoaddition of psoralens, 254 nm ultraviolet radiation, and nitrogen mustards was determined in diploid cells homozygous for the pso3-1 mutation and in the corresponding wild type of Saccharomyces cerevisiae. For these different agents, the frequency of non-reciprocal events (conversion) is reduced in the pso3-1 mutant compared to the wild type. In contrast, the frequency of reciprocal events (crossing-over) is increased at a range of doses. These observations, together with the block in induced mutagenesis for both reverse and forward mutations previously reported for the pso3-1 mutant, suggest that the PS03 gene product plays a role in mismatch repair of short patch regions. The block in gene conversion in the pso3 homozygous diploid leads, in the case of nitrogen mustards, to specific repair intermediates which are lethal to the cells.     

The sources of variation for individual prey-to-predator size ratios

The relative body size at which predators are willing to attack prey, a key trait for predator-prey interactions, is usually considered invariant. However, this ratio can vary widely among individuals or populations. Identifying the range and origin of such variation is key to understanding the strength and constraints on selection in both predators and prey. Still, these sources of variation remain largely unknown. We filled this gap by measuring the genetic, maternal and environmental variation of the maximum prey-to-predator size ratio (PPSR_max) in juveniles of the wolf spider Lycosa fasciiventris using a paternal half-sib split-brood design, in which each male was paired with two females and the offspring reared in two food environments: poor and rich. Each juvenile spider was then sequentially offered crickets of decreasing size and the maximum prey size killed was determined. We also measured body size and body condition of spiders upon emergence and just before the trial. We found low, but significant heritability (h² = 0.069) and dominance and common environmental variance (d² + 4c² = 0.056). PPSR_max was also partially explained by body condition (during trial) but there was no effect of the rearing food environment. Finally, a maternal correlation between body size early in life and PPSR_max indicated that offspring born larger were less predisposed to feed on larger prey later in life. Therefore, PPSR_max, a central trait in ecosystems, can vary widely and this variation is due to different sources, with important consequences for changes in this trait in the short and long terms.Subject terms: Evolutionary biology, Behavioural ecology, Heritable quantitative trait, Evolutionary ecology     

Environmental pH modulates biofilm formation and matrix composition in Candida albicans and Candida glabrata

Abstract

Candida species are fungal opportunistic pathogens capable of colonizing and infecting various human anatomical sites, where they have to adapt to distinct niche-specific pH conditions. The aim of this study was to analyse the features of Candida albicans and Candida glabrata biofilms developed under neutral and vaginal acidic (pH 4) conditions. C. albicans produced thicker and more filamentous biofilms under neutral than under acidic conditions. On the other hand, the formation of biofilms by C. glabrata was potentiated by the acidic conditions suggesting the high adaptability of this species to the vaginal environment. In general, both species developed biofilms containing higher amounts of matrix components (protein and carbohydrate) under neutral than acidic conditions, although the opposite result was found for one C. glabrata strain. Overall, this study contributes to a better understanding of the modulation of C. albicans and C. glabrata virulence by specific pH conditions.