Chibana H, Beckerman J L, Magee P T
Department of Genetics, Cell Biology, and Development, University of Minnesota, St. Paul, Minnesota 55108, USA.
Genome Res. 2000 Dec;10(12):1865-77. doi: 10.1101/gr.148600.
It has been suggested that Candida albicans, a diploid asexual fungus, achieves genetic diversity by genomic rearrangement. This important human pathogen may provide a system in which to analyze alternate routes to genomic diversity. C. albicans has a highly variable karyotype; its chromosomes contain a middle repeated DNA sequence called the Major Repeat Sequence (MRS), composed of subrepeats HOK, RPS, and RB2. RPS is tandemly repeated while the other subrepeats occur once in each MRS. Chromosome 7, the smallest of the eight chromosomes, has been previously mapped. The complete physical map of this chromosome was used to analyze chromosome 7 diversity in six strains, including two well-characterized laboratory strains (1006 and WO-1) and four clinical ones. We found four types of events to explain the genomic diversity: 1) Chromosome length polymorphism (CLP) results from expansion and contraction of the RPS; 2) reciprocal translocation occurs at the MRS loci; 3) chromosomal deletion; and (4) trisomy of individual chromosomes. These four phenomena play an important role in generating genomic diversity in C. albicans.
有人提出，白色念珠菌作为一种二倍体无性真菌，通过基因组重排实现遗传多样性。这种重要的人类病原体可能提供了一个分析基因组多样性替代途径的系统。白色念珠菌具有高度可变的核型；其染色体包含一种称为主要重复序列（MRS）的中度重复DNA序列，由亚重复序列HOK、RPS和RB2组成。RPS是串联重复的，而其他亚重复序列在每个MRS中只出现一次。7号染色体是八条染色体中最小的，此前已被定位。利用该染色体的完整物理图谱分析了六个菌株中7号染色体的多样性，其中包括两个特征明确的实验室菌株（1006和WO-1）和四个临床菌株。我们发现了四种事件来解释基因组多样性：1）染色体长度多态性（CLP）是由RPS的扩增和收缩引起的；2）相互易位发生在MRS位点；3）染色体缺失；以及（4）单个染色体的三体性。这四种现象在白色念珠菌基因组多样性的产生中起着重要作用。
