Fernandes O, Murthy V K, Kurath U, Degrave W M, Campbell D A
Department of Microbiology and Immunology, University of California, Los Angeles 90024.
Mol Biochem Parasitol. 1994 Aug;66(2):261-71. doi: 10.1016/0166-6851(94)90153-8.
We have used polymerase chain reaction to amplify the mini-exon gene repeat from 18 Leishmania strains. DNA sequence analysis of the cloned products reveals high conservation of both the exon and intron (i.e. transcribed region). In contrast, variation is evident in both the length and primary sequence of the non-transcribed spacers. Dermotropic species of the New World subgenus Leishmania possess a 0.3-kb gene that differs from the 0.25-kb gene of New World dermotropic species of the subgenus Viannia. The Old/New World viscerotropic species and Old World dermotropic species possess a 0.4-kb mini-exon gene. However, the genes from the viscerotropic and dermotropic groups may be distinguished on the basis of sequence differences in the non-transcribed spacer. Comparative analysis of the -86 to -1 region from all species has been used to measure relatedness within the genus. In general, all the observed differences correlate with the four major groups of Leishmania (New World dermotropic Leishmania, New World dermotropic Viannia, Old World dermotropic Leishmania and viscerotropic Leishmania). Two of the three repeats cloned from L. donovani show short deletions. The missing sequence is flanked by direct, 7-bp repeats suggesting that the sequences may have been deleted by homologous recombination. Such rearrangements could account for the diversity detected in the non-transcribed spacers of the mini-exon genes.
我们利用聚合酶链反应从18株利什曼原虫菌株中扩增出小外显子基因重复序列。对克隆产物的DNA序列分析显示，外显子和内含子（即转录区域）都具有高度保守性。相比之下，非转录间隔区的长度和一级序列均存在明显变异。新大陆利什曼原虫亚属的嗜皮物种拥有一个0.3 kb的基因，与维安亚属新大陆嗜皮物种的0.25 kb基因不同。新旧大陆的内脏利什曼原虫物种和旧大陆嗜皮物种拥有一个0.4 kb的小外显子基因。然而，可根据非转录间隔区的序列差异区分内脏利什曼原虫和嗜皮利什曼原虫这两组的基因。对所有物种-86至-1区域的比较分析已用于衡量该属内的亲缘关系。一般而言，所有观察到的差异都与利什曼原虫的四大类群（新大陆嗜皮利什曼原虫、新大陆嗜皮维安亚属、旧大陆嗜皮利什曼原虫和内脏利什曼原虫）相关。从杜氏利什曼原虫克隆的三个重复序列中有两个显示出短缺失。缺失序列两侧是直接的7 bp重复序列，这表明这些序列可能是通过同源重组而缺失的。这种重排可能解释了在小外显子基因非转录间隔区检测到的多样性。
