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Adaptive response to DNA-damaging agents in natural Saccharomyces cerevisiae populations from "Evolution Canyon", Mt. Carmel, Israel.

Lidzbarsky GA, Shkolnik T, Nevo E - PLoS ONE (2009)

Bottom Line: Carmel, Israel).We exposed our strains to the different DNA-damaging agents and measured survival by counting colony forming units.The strains from the "African" slope were more resilient to both UVA and MMS than the strains from the "European" slope.

View Article: PubMed Central - PubMed

Affiliation: Institute of Evolution, Department of Evolutionary and Environmental Biology, Faculty of Science and Science Education, University of Haifa, Haifa, Israel.

ABSTRACT

Background: Natural populations of most organisms, especially unicellular microorganisms, are constantly exposed to harsh environmental factors which affect their growth. UV radiation is one of the most important physical parameters which influences yeast growth in nature. Here we used 46 natural strains of Saccharomyces cerevisiae isolated from several natural populations at the "Evolution Canyon" microsite (Nahal Oren, Mt. Carmel, Israel). The opposing slopes of this canyon share the same geology, soil, and macroclimate, but they differ in microclimatic conditions. The interslope differences in solar radiation (200%-800% more on the "African" slope) caused the development of two distinct biomes. The south-facing slope is sunnier and has xeric, savannoid "African" environment while the north-facing slope is represented by temperate, "European" forested environment. Here we studied the phenotypic response of the S. cerevisiae strains to UVA and UVC radiations and to methyl methanesulfonate (MMS) in order to evaluate the interslope effect on the strains' ability to withstand DNA-damaging agents.

Methodology/principal findings: We exposed our strains to the different DNA-damaging agents and measured survival by counting colony forming units. The strains from the "African" slope were more resilient to both UVA and MMS than the strains from the "European" slope. In contrast, we found that there was almost no difference between strains (with similar ploidy) from the opposite slopes, in their sensitivity to UVC radiation. These results suggest that the "African" strains are more adapted to higher solar radiation than the "European" strains. We also found that the tetraploids strains were more tolerant to all DNA-damaging agents than their neighboring diploid strains, which suggest that high ploidy level might be a mechanism of adaptation to high solar radiation.

Conclusions/significance: Our results and the results of parallel studies with several other organisms, suggest that natural selection appears to select, at a microscale, for adaptive complexes that can tolerate the higher UV radiation on the "African" slope.

Show MeSH
Survival rates of the “African” (AS) and “European” (ES) diploid strains (UVC radiation).The AS strains are colored in black and the ES strains are colored in gray. Bars represent standard errors.
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pone-0005914-g006: Survival rates of the “African” (AS) and “European” (ES) diploid strains (UVC radiation).The AS strains are colored in black and the ES strains are colored in gray. Bars represent standard errors.

Mentions: The total averaged survival rate of the “African” slope strains (sites AS1, AS2, and AS3) was nearly the same as the total averaged survival rate of the “European” slope strains (sites ES5, ES6, and ES7) (Fig. 4). As in the UVA assay, the ploidy level had an effect on the survival of the strains. The total survival rates of the tetraploid and triploid was significantly higher than the total survival rates of the diploid strains (Kruskal-Wallis test, p<0.001). The survival rates of the “African” diploid and tetraploid strains were not significantly different than the survival rates of the equivalent “European” strains (Figs. 5–6 and Fig. S3) although the similarity between the survival rates of the diploid strains was contributed by a single irregular strain, which reduced the survival rate of the “African” diploids (Fig. 6). Without this strain, the “African” diploids are significantly more resilient to UVC radiation than the “European” diploids (p = 0.002). As in the UVA assay, for both slopes, the tetraploid strains were significantly more resilient to UVC radiation than the neighboring diploid strains (Mann Whitney test, AS: p = 0.022, ES: p<0.001).


Adaptive response to DNA-damaging agents in natural Saccharomyces cerevisiae populations from "Evolution Canyon", Mt. Carmel, Israel.

Lidzbarsky GA, Shkolnik T, Nevo E - PLoS ONE (2009)

Survival rates of the “African” (AS) and “European” (ES) diploid strains (UVC radiation).The AS strains are colored in black and the ES strains are colored in gray. Bars represent standard errors.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2690839&req=5

pone-0005914-g006: Survival rates of the “African” (AS) and “European” (ES) diploid strains (UVC radiation).The AS strains are colored in black and the ES strains are colored in gray. Bars represent standard errors.
Mentions: The total averaged survival rate of the “African” slope strains (sites AS1, AS2, and AS3) was nearly the same as the total averaged survival rate of the “European” slope strains (sites ES5, ES6, and ES7) (Fig. 4). As in the UVA assay, the ploidy level had an effect on the survival of the strains. The total survival rates of the tetraploid and triploid was significantly higher than the total survival rates of the diploid strains (Kruskal-Wallis test, p<0.001). The survival rates of the “African” diploid and tetraploid strains were not significantly different than the survival rates of the equivalent “European” strains (Figs. 5–6 and Fig. S3) although the similarity between the survival rates of the diploid strains was contributed by a single irregular strain, which reduced the survival rate of the “African” diploids (Fig. 6). Without this strain, the “African” diploids are significantly more resilient to UVC radiation than the “European” diploids (p = 0.002). As in the UVA assay, for both slopes, the tetraploid strains were significantly more resilient to UVC radiation than the neighboring diploid strains (Mann Whitney test, AS: p = 0.022, ES: p<0.001).

Bottom Line: Carmel, Israel).We exposed our strains to the different DNA-damaging agents and measured survival by counting colony forming units.The strains from the "African" slope were more resilient to both UVA and MMS than the strains from the "European" slope.

View Article: PubMed Central - PubMed

Affiliation: Institute of Evolution, Department of Evolutionary and Environmental Biology, Faculty of Science and Science Education, University of Haifa, Haifa, Israel.

ABSTRACT

Background: Natural populations of most organisms, especially unicellular microorganisms, are constantly exposed to harsh environmental factors which affect their growth. UV radiation is one of the most important physical parameters which influences yeast growth in nature. Here we used 46 natural strains of Saccharomyces cerevisiae isolated from several natural populations at the "Evolution Canyon" microsite (Nahal Oren, Mt. Carmel, Israel). The opposing slopes of this canyon share the same geology, soil, and macroclimate, but they differ in microclimatic conditions. The interslope differences in solar radiation (200%-800% more on the "African" slope) caused the development of two distinct biomes. The south-facing slope is sunnier and has xeric, savannoid "African" environment while the north-facing slope is represented by temperate, "European" forested environment. Here we studied the phenotypic response of the S. cerevisiae strains to UVA and UVC radiations and to methyl methanesulfonate (MMS) in order to evaluate the interslope effect on the strains' ability to withstand DNA-damaging agents.

Methodology/principal findings: We exposed our strains to the different DNA-damaging agents and measured survival by counting colony forming units. The strains from the "African" slope were more resilient to both UVA and MMS than the strains from the "European" slope. In contrast, we found that there was almost no difference between strains (with similar ploidy) from the opposite slopes, in their sensitivity to UVC radiation. These results suggest that the "African" strains are more adapted to higher solar radiation than the "European" strains. We also found that the tetraploids strains were more tolerant to all DNA-damaging agents than their neighboring diploid strains, which suggest that high ploidy level might be a mechanism of adaptation to high solar radiation.

Conclusions/significance: Our results and the results of parallel studies with several other organisms, suggest that natural selection appears to select, at a microscale, for adaptive complexes that can tolerate the higher UV radiation on the "African" slope.

Show MeSH