Pirritano Marcello, Yakovleva Yulia, Potekhin Alexey, Simon Martin
Molecular Cell Biology and Microbiology, School of Mathematics and Natural Sciences, University of Wuppertal, 42119 Wuppertal, Germany.
Laboratory of Cellular and Molecular Protistology, Zoological Institute of Russian Academy of Sciences, 190121 Saint Petersburg, Russia.
Microorganisms. 2022 Nov 30;10(12):2378. doi: 10.3390/microorganisms10122378.
is a free-living ciliate that undergoes antigenic variation and still the functions of these variable surface antigen coats in this non-pathogenic ciliate remain elusive. Only a few surface antigen genes have been described, mainly in the two model species strain 51 and strain 156. Given the lack of suitable sequence data to allow for phylogenetics and deeper sequence comparisons, we screened the genomes of six different species for serotype genes and isolated 548 candidates. Our approach identified the subfamilies of the isogenes of individual serotypes that were mostly represented by intrachromosomal gene duplicates. These showed different duplication levels, and chromosome synteny suggested rather young duplication events after the emergence of the species complex, indicating a rapid evolution of surface antigen genes. We were able to identify the different subfamilies of the surface antigen genes with internal tandem repeats, which showed consensus motifs across species. The individual isogene families showed additional consensus motifs, indicating that the selection pressure holds individual amino acids constant in these repeats. This may be a hint of the receptor function of these antigens rather than a presentation of random epitopes, generating the variability of these surface molecules.
是一种自由生活的纤毛虫，会发生抗原变异，然而在这种非致病性纤毛虫中，这些可变表面抗原包膜的功能仍然难以捉摸。仅描述了少数表面抗原基因，主要是在两个模式物种51株和156株中。由于缺乏合适的序列数据以进行系统发育分析和更深入的序列比较，我们筛选了六个不同物种的基因组以寻找血清型基因，并分离出548个候选基因。我们的方法确定了各个血清型等基因的亚家族，这些亚家族大多由染色体内基因重复代表。这些显示出不同的重复水平，并且染色体同线性表明在该物种复合体出现后发生了相当年轻的重复事件，表明表面抗原基因的快速进化。我们能够鉴定出具有内部串联重复的表面抗原基因的不同亚家族，这些亚家族在物种间显示出共有基序。各个等基因家族显示出额外的共有基序，表明选择压力使这些重复中的个别氨基酸保持恒定。这可能暗示了这些抗原的受体功能，而不是随机表位的呈现，从而产生了这些表面分子的变异性。
