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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
Averaged survival rates of the “African” (AS) and “European” (ES) diploid and tetraploid strains (UVA radiation). The diploids sample size is 7 for each slope. The tetraploids sample size is 14 for the AS and 13 for the ES. Bars represent standard errors. The survival rate of the “African” diploids was significantly higher than the survival rate of the “European” diploids. (Mann-Whitney test, p = 0.004). The survival rate of the “African” tetraploids was significantly higher than the survival rate of the “European” tetraploids. (Mann-Whitney test, p = 0.001). The survival rate of the “African” diploids was not significantly different than the survival rate of the “European” tetraploids (Mann-Whitney test, p = 0.81).
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pone-0005914-g003: Averaged survival rates of the “African” (AS) and “European” (ES) diploid and tetraploid strains (UVA radiation). The diploids sample size is 7 for each slope. The tetraploids sample size is 14 for the AS and 13 for the ES. Bars represent standard errors. The survival rate of the “African” diploids was significantly higher than the survival rate of the “European” diploids. (Mann-Whitney test, p = 0.004). The survival rate of the “African” tetraploids was significantly higher than the survival rate of the “European” tetraploids. (Mann-Whitney test, p = 0.001). The survival rate of the “African” diploids was not significantly different than the survival rate of the “European” tetraploids (Mann-Whitney test, p = 0.81).

Mentions: To see whether the ploidy level had an impact on the strains' survival, we analyzed the results comparing ploidy groups. The results showed that the ploidy level did affect the survival of the strains, as the total survival rates of the tetraploid and triploid were significantly higher than the total survival rates of the diploid strains (Kruskal-Wallis test, p<0.001), although there was no significant difference in the survival rates of the tetraploid and the triploid strains (Mann Whitney test, p = 0.54). When the diploid and the tetraploid strains from both slopes were compared separately, results showed that the survival rates of the “African” diploid and tetraploid strains were significantly higher than the survival rates of the matching “European” strains (Fig. 3 and Figs. S1-S2). On both slopes, the tetraploid strains were significantly more resilient to UVA radiation than the neighboring diploid strains (Mann Whitney test, AS: p = 0.02, ES: p<0.001), however, there was no significant difference between the “African” diploids and the “European” tetraploids (Man-Whitney test, p = 0.81).


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)

Averaged survival rates of the “African” (AS) and “European” (ES) diploid and tetraploid strains (UVA radiation). The diploids sample size is 7 for each slope. The tetraploids sample size is 14 for the AS and 13 for the ES. Bars represent standard errors. The survival rate of the “African” diploids was significantly higher than the survival rate of the “European” diploids. (Mann-Whitney test, p = 0.004). The survival rate of the “African” tetraploids was significantly higher than the survival rate of the “European” tetraploids. (Mann-Whitney test, p = 0.001). The survival rate of the “African” diploids was not significantly different than the survival rate of the “European” tetraploids (Mann-Whitney test, p = 0.81).
© Copyright Policy
Related In: Results  -  Collection

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

pone-0005914-g003: Averaged survival rates of the “African” (AS) and “European” (ES) diploid and tetraploid strains (UVA radiation). The diploids sample size is 7 for each slope. The tetraploids sample size is 14 for the AS and 13 for the ES. Bars represent standard errors. The survival rate of the “African” diploids was significantly higher than the survival rate of the “European” diploids. (Mann-Whitney test, p = 0.004). The survival rate of the “African” tetraploids was significantly higher than the survival rate of the “European” tetraploids. (Mann-Whitney test, p = 0.001). The survival rate of the “African” diploids was not significantly different than the survival rate of the “European” tetraploids (Mann-Whitney test, p = 0.81).
Mentions: To see whether the ploidy level had an impact on the strains' survival, we analyzed the results comparing ploidy groups. The results showed that the ploidy level did affect the survival of the strains, as the total survival rates of the tetraploid and triploid were significantly higher than the total survival rates of the diploid strains (Kruskal-Wallis test, p<0.001), although there was no significant difference in the survival rates of the tetraploid and the triploid strains (Mann Whitney test, p = 0.54). When the diploid and the tetraploid strains from both slopes were compared separately, results showed that the survival rates of the “African” diploid and tetraploid strains were significantly higher than the survival rates of the matching “European” strains (Fig. 3 and Figs. S1-S2). On both slopes, the tetraploid strains were significantly more resilient to UVA radiation than the neighboring diploid strains (Mann Whitney test, AS: p = 0.02, ES: p<0.001), however, there was no significant difference between the “African” diploids and the “European” tetraploids (Man-Whitney test, p = 0.81).

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