Mild environmental stress elicits mutations affecting fitness in Chlamydomonas
Mild environmental stress elicits mutations affecting fitness in Chlamydomonas
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DOI：
10.1098/rspb.2000.0976
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发表时间：
2000-01-22
影响因子：
4.7
通讯作者：
Bell, G
中科院分区：
文献类型：
--
作者：
Goho, S;Bell, G
将衣藻培养物暴露在一系列相对温和的胁迫下24小时，这些胁迫包括高温和低温、渗透胁迫、低pH、饥饿和毒性胁迫。然后让它们在接近最佳的条件下在未修饰的最小培养基中恢复大约10个营养代。然后用分离细胞在琼脂上的分裂率来测定适应度。我们发现，与在未修饰的最小培养基中培养的阴性对照相比，应激培养的平均适应度较低，适应度的标准化方差较大。正如预期的那样，接受致突变剂量紫外线照射的阳性对照也显示出同样的趋势。我们得出结论，对这些观察结果最合理的解释是，轻微的压力增加了基因组的突变率。这似乎是第一次在真核生物中发现这种现象。这种反应可能是适应性的，因为由于压力而引起较高突变率的谱系可以通过产生少数碰巧很好地适应压力环境的突变体而得到有利的选择。不过，也不排除其他解释。无论涉及的机制如何，压力下突变率的提高将影响对环境变化的进化反应速度，也会影响性的维持。
Cultures of Chlamydomonas were exposed to a range of relatively mild stresses for a period of 24 h. These stresses comprised high and low temperatures, osmotic stress, low pH, starvation and toxic stress. They were then allowed to recuperate for around ten vegetative generations under near-optimal conditions in unmodified minimal medium. Fitness was then assayed as the rate of division of isolated cells on agar. We found that there was a strong tendency for stressed cultures to have lower mean fitness and greater standardized variance in fitness than the negative controls which had been cultured throughout in unmodified minimal medium. The same tendency was shown, as expected, by positive controls which received mutagenic doses of ultraviolet irradiation. We concluded that the most reasonable interpretation of these observations is that mild stress increases the genomic rate of mutation. This appears to be the first time that this phenomenon has been noticed in eukaryotes. The response might be adaptive because lineages in which higher mutation rates are elicited by stress can be favourably selected through the production of a few mutants which are fortuitously well adapted to the stressful environment. Other interpretations are not excluded, however. Regardless of the mechanism involved, the elevation of mutation rates under stress will affect the rate of evolutionary response to environmental change and also the maintenance of sexuality.