KARYOTYPIC REARRANGEMENTS IN CANDIDA ALBICANS

本建议中概述的研究的长期目标是 了解成功发病机制背后的机制， 二型无性二倍体酵母，白色念珠菌。这种酵母会导致 从粘膜鹅口疮到全身性真菌血症的感染。 在 免疫功能低下的患者，白色念珠菌感染是生命， 威胁。没有已知的该微生物的毒力因子，导致 结论是其致病性是一个非常复杂的现象。一 可能在毒力中起作用的生物学方面是C. 白色念珠菌改变其核型。据推测，这种核型 不稳定性可能提供遗传变异的手段。 核型变异的机制尚不清楚。表现在 染色体长度和染色体易位的变化。的目的 本研究旨在探讨C. 白色念珠菌有待检验的假设是染色体重排 优先发生在称为RPS的重复序列上。为了验证这一 假设，已知染色体易位的连接点将是 克隆并鉴定，以确定是否在 断点。将构建质粒重组系统以测试 对于基因组中同源序列之间的重组频率， 是否存在RPS。异等位基因间插入 将测试异源染色体上的RPS， 增加了这些事件的频率。最后， 将克隆在测试系统中发生的易位， 其特征在于，观察结构是否与 假说.因为核型重排似乎更频繁 在经历表型转变的菌株中， 将在“切换”和“非切换”中执行上述操作。 菌株，看看是否易位确实在前者升高 与后者相比。 这些实验将提供有关C.白色念珠菌， 这将是有用的信息，在各种研究的影响， 病原体的致病性，包括表型的检查 不稳定性和适应宿主的各种生态位。他们还将 对开发这种重要病原体的遗传学有很大帮助。

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.