The population biology and evolutionary significance of Ty elements in Saccharomyces cerevisiae.
The population biology and evolutionary significance of Ty elements in Saccharomyces cerevisiae.
复制标题
酿酒酵母 Ty 元件的群体生物学和进化意义。
作者：
Wilke,CM;Maimer,E;Adams,J
Ty元素的基本结构和性质被认为是特别提到他们的角色作为代理人的进化变化。Ty元件可以通过其作为诱变剂的作用以及通过提供用于重组的可移植同源性区域来产生适合性的遗传变异。由Ty 1转座事件产生的突变谱可能由于其靶特异性和基因调控能力而具有比由其他类型的突变过程产生的谱更高的适应性有利突变频率。实验室菌株含有25-35个元件，在这些菌株和工业菌株中，插入似乎相当稳定。相比之下，在野生分离株中看到Ty数量的广泛变化，具有较低的平均数量/基因组。可能决定群体中Ty拷贝数的因素包括转座率（取决于Ty拷贝数和交配类型）、基因组中Ty元件的稳定性以及对基因组中Ty插入的选择。虽然Ty转座的平均效应是有害的，但用含有单个Ty元件的单个克隆起始的群体稳定地积累了超过1，000代的Ty元件。Ty转座事件可以被选择性地支持的直接证据由实验提供，在该实验中，包含大量Ty 1拷贝数变异性的群体在同质环境中维持了100代。在其终止时，含0 Ty元件的克隆的频率已下降到10.0，并且群体已由少数含>0 Ty元件的克隆占优势。在结构化环境中维持的群体中没有观察到这种变异性的降低，尽管观察到了Ty数的变化。遗传（交配型和倍性）的变化和环境波动的长期持久性的Ty元素在S。讨论了政党的种类。
The basic structure and properties of Ty elements are considered with special reference to their role as agents of evolutionary change. Ty elements may generate genetic variation for fitness by their action as mutagens, as well as by providing regions of portable homology for recombination. The mutational spectra generated by Ty 1 transposition events may, due to their target specificity and gene regulatory capabilities, possess a higher frequency of adaptively favorable mutations than spectra resulting from other types of mutational processes. Laboratory strains contain between 25–35 elements, and in both these and industrial strains the insertions appear quite stable. In contrast, a wide variation in Ty number is seen in wild isolates, with a lower average number/genome. Factors which may determine Ty copy number in populations include transposition rates (dependent on Ty copy number and mating type), and stabilization of Ty elements in the genome as well as selection for and against Ty insertions in the genome. Although the average effect of Ty transpositions are deleterious, populations initiated with a single clone containing a single Ty element steadily accumulated Ty elements over 1,000 generations. Direct evidence that Ty transposition events can be selectively favored is provided by experiments in which populations containing large amounts of variability for Ty1 copy number were maintained for ∼100 generations in a homogeneous environment. At their termination, the frequency of clones containing 0 Ty elements had decreased to ∼0.0, and the populations had became dominated by a small number of clones containing >0 Ty elements. No such reduction in variability was observed in populations maintained in a structured environment, though changes in Ty number were observed. The implications of genetic (mating type and ploidy) changes and environmental fluctuations for the long-term persistence of Ty elements within theS. cerevisiaespecies group are discussed.