KARYOTYPIC REARRANGEMENTS IN CANDIDA ALBICANS

这项建议中概述的研究的长期目标是 了解成功致病的机制 二形性无性二倍体酵母，白色念珠菌。这种酵母菌引起 感染范围从黏膜鹅口疮到全身性真菌血症。在……里面 免疫功能低下的患者，感染白色念珠菌是生命- 具有威胁性。目前还不知道这种有机体的毒力因子，导致 结论是它的致病性是一个非常复杂的现象。一 在毒力方面可能起作用的生物学方面是C。 白念珠菌改变其核型。据推测，这种核型 不稳定可能提供了一种遗传变异的手段。 核型变异的机制尚不清楚。它体现在 染色体长度和染色体易位的变化。的目的是 本课题的目的是研究华南星的核型变异机制。 白念珠菌。需要检验的假设是染色体重排 优先发生在称为RPS的重复序列中。为了测试这一点 假设，已知染色体易位的连接点将是 克隆并鉴定以查看重复序列是否在 断点。将建造PIASMID重组系统以测试 中的同源序列之间的重组频率 RPS的存在和缺失。插入的异等位基因间的重组 将对异源染色体进行检测，以查看RPS 增加这些事件的发生频率。最后，两个城市的结合点 在测试系统中发生的易位将被克隆并 其特征是查看结构是否与 假设。因为核型重排似乎更加频繁 在经历表型转变的菌株中，实验 上述将在“切换”和“非切换”中执行 以观察易位是否确实在前者中升高 与后者相比。 这些实验将提供关于白色念珠菌重组的信息， 对各种研究有用的信息，这些研究与 生物体的致病性，包括表型的检查 对寄主中各种生态位的不稳定和适应。他们还将 对发展这种重要病原体的遗传学有很大的帮助。

The long-term objectives of the research outlined in this proposal are to understand the mechanisms which lie behind the successful pathogenesis of the dimorphic asexual diploid yeast, Candida albicans. This yeast causes infections ranging from mucosal thrush to systemic fungemia. In immunocompromised patients, infections by Candida albicans are life- threatening. No virulence factors are known for this organism, leading to the conclusion that its pathogenicity is a very complex phenomenon. One aspect of biology which may play a role in virulence is the capacity of C. albicans to vary its karyotype. It has been speculated that this karyotypic instability may provide a means of genetic variation. The mechanism of the karyotypic variation is unknown. It is manifested in changes in chromosomal length and in chromosomal translocations. The aim of this project is to investigate the mechanism of karyotypic variation in C. albicans. The hypothesis to be tested is that chromosomal rearrangements take place preferentially at a repeated sequence called RPS. To test this hypothesis, the junction points of known chromosomal translocations will be cloned and characterized to see whether the repeated sequence is found at the breakpoints. PIasmid recombination systems will be constructed to test for the frequencies of recombination between homologous sequences in the presence and absence of RPS. Recombination between heteroalleles inserted on heterologous chromosomes will be tested in order to see whether RPS increases the frequency of these events. Finally, the junctions of translocations which have occurred in the test system will be cloned and characterized to see whether the structure is consistent with the hypothesis. Because karyotypic rearrangement seems to be much more frequent in strains which undergo the phenotypic transition, the experiments described above will be carried out in "switching" and "non-switching" strains, to see whether translocation is indeed elevated in the former compared to the latter. These experiments will give information on recombination in C. albicans, information which will be useful in a variety of studies bearing on the pathogenicity of the organism, including the examination of phenotypic instability and adaptation to various niches in the host. They will also greatly aid in developing the genetics of this important pathogen.