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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
MMS sensitivity assay with diploid strains.In the three pictures the “African” diploid strains are on the left side of the picture, and the “European” diploid strains are on the right (n = 7 for each slope). (A) YPD plates containing 0.01% MMS. (B) YPD plates containing 0.03% MMS. (C) YPD plates containing 0.05% MMS.
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pone-0005914-g007: MMS sensitivity assay with diploid strains.In the three pictures the “African” diploid strains are on the left side of the picture, and the “European” diploid strains are on the right (n = 7 for each slope). (A) YPD plates containing 0.01% MMS. (B) YPD plates containing 0.03% MMS. (C) YPD plates containing 0.05% MMS.

Mentions: The “African” and “European” diploid strains showed different sensitivity to different MMS concentrations. All diploid strains were able to grow well on plates containing 0.01% MMS (Fig. 7-A). However, when the diploid strains were challenged by MMS concentration of 0.03% the “African” strains were more resilient than the “European” strains (Fig. 7-B). Similar trend was observed when the tetraploid strains were challenged with 0.03% MMS. The “African” strains grew better than the “European” strains (Fig. 8-A). As in the UV assays, for both slopes, the tetraploid strains were more resilient to 0.03% MMS than the neighboring diploid strains, and the “African” diploid strains were more resilient to 0.03% MMS than the “European” tetraploid strains. All strains, diploid and tetraploid, showed poor growth ability on plates containing 0.05% MMS although the spots created by the “African” strains seemed bigger and rounder (Fig. 7-C and Fig. 8-B)


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)

MMS sensitivity assay with diploid strains.In the three pictures the “African” diploid strains are on the left side of the picture, and the “European” diploid strains are on the right (n = 7 for each slope). (A) YPD plates containing 0.01% MMS. (B) YPD plates containing 0.03% MMS. (C) YPD plates containing 0.05% MMS.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0005914-g007: MMS sensitivity assay with diploid strains.In the three pictures the “African” diploid strains are on the left side of the picture, and the “European” diploid strains are on the right (n = 7 for each slope). (A) YPD plates containing 0.01% MMS. (B) YPD plates containing 0.03% MMS. (C) YPD plates containing 0.05% MMS.
Mentions: The “African” and “European” diploid strains showed different sensitivity to different MMS concentrations. All diploid strains were able to grow well on plates containing 0.01% MMS (Fig. 7-A). However, when the diploid strains were challenged by MMS concentration of 0.03% the “African” strains were more resilient than the “European” strains (Fig. 7-B). Similar trend was observed when the tetraploid strains were challenged with 0.03% MMS. The “African” strains grew better than the “European” strains (Fig. 8-A). As in the UV assays, for both slopes, the tetraploid strains were more resilient to 0.03% MMS than the neighboring diploid strains, and the “African” diploid strains were more resilient to 0.03% MMS than the “European” tetraploid strains. All strains, diploid and tetraploid, showed poor growth ability on plates containing 0.05% MMS although the spots created by the “African” strains seemed bigger and rounder (Fig. 7-C and Fig. 8-B)

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