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Segregation Lag in Polyploid Cells of the Pathogen Genus Borrelia: Implications for Antigenic Variation?.

ABSTRACT: Relapsing fever agents like Borrelia hermsii undergo multiphasic antigenic variation that is attributable to spontaneous DNA non-reciprocal transpositions at a particular locus in the genome. This genetic switch results in a new protein being expressed on the cell surface, allowing cells with that phenotype to escape prevailing immunity. But the switch occurs in only one of several genomes in these spirochetes, and a newly-switched gene is effectively "recessive" until homozygosity is achieved. The longer that descendants of the switched cell expressed both old and new proteins, the longer this lineage risks neutralization by antibody to the old protein. We investigated the implications for antigenic variation of the phenotypic lag that polyploidy would confer on cells. We first experimentally determined the average genome copy number in daughter cells after division during mouse infection with B. hermsii strain HS1. We then applied discrete deterministic and stochastic simulations to predict outcomes when genomes were equably segregated either linearly, i.e. according to their position in one-dimensional arrays, or randomly partitioned, as for a sphere. Linear segregation replication provided for a lag in achievement of homozygosity that was significantly shorter than could be achieved under the random segregation condition. For cells with 16 genomes, this would be a 4-generation lag. A model incorporating the immune response and evolved matrices of switch rates indicated a greater fitness for polyploid over monoploid bacteria in terms of duration of infection.

SUBMITTER: Crowder CD

PROVIDER: S-EPMC5482298 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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Segregation Lag in Polyploid Cells of the Pathogen Genus <i>Borrelia</i>: Implications for Antigenic Variation .

Crowder Christopher D CD Denny Richard L RL Barbour Alan G AG

The Yale journal of biology and medicine 20170623 2

Relapsing fever agents like <i>Borrelia hermsii</i> undergo multiphasic antigenic variation that is attributable to spontaneous DNA non-reciprocal transpositions at a particular locus in the genome. This genetic switch results in a new protein being expressed on the cell surface, allowing cells with that phenotype to escape prevailing immunity. But the switch occurs in only one of several genomes in these spirochetes, and a newly-switched gene is effectively "recessive" until homozygosity is ach ...[more]

PMID: 28656008

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Project description:BACKGROUND: Paspalum (Poaceae) is an important genus of the tribe Paniceae, which includes several species of economic importance for foraging, turf and ornamental purposes, and has a complex taxonomical classification. Because of the widespread interest in several species of this genus, many accessions have been conserved in germplasm banks and distributed throughout various countries around the world, mainly for the purposes of cultivar development and cytogenetic studies. Correct identification of germplasms and quantification of their variability are necessary for the proper development of conservation and breeding programs. Evaluation of microsatellite markers in different species of Paspalum conserved in a germplasm bank allowed assessment of the genetic differences among them and assisted in their proper botanical classification. RESULTS: Seventeen new polymorphic microsatellites were developed for Paspalum atratum Swallen and Paspalum notatum Flüggé, twelve of which were transferred to 35 Paspalum species and used to evaluate their variability. Variable degrees of polymorphism were observed within the species. Based on distance-based methods and a Bayesian clustering approach, the accessions were divided into three main species groups, two of which corresponded to the previously described Plicatula and Notata Paspalum groups. In more accurate analyses of P. notatum accessions, the genetic variation that was evaluated used thirty simple sequence repeat (SSR) loci and revealed seven distinct genetic groups and a correspondence of these groups to the three botanical varieties of the species (P. notatum var. notatum, P. notatum var. saurae and P. notatum var. latiflorum). CONCLUSIONS: The molecular genetic approach employed in this study was able to distinguish many of the different taxa examined, except for species that belong to the Plicatula group, which has historically been recognized as a highly complex group. Our molecular genetic approach represents a valuable tool for species identification in the initial assessment of germplasm as well as for characterization, conservation and successful species hybridization.

Dataset Information

Segregation Lag in Polyploid Cells of the Pathogen Genus Borrelia: Implications for Antigenic Variation?.

Publications

Segregation Lag in Polyploid Cells of the Pathogen Genus <i>Borrelia</i>: Implications for Antigenic Variation .

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Dataset Information

Segregation Lag in Polyploid Cells of the Pathogen Genus Borrelia: Implications for Antigenic Variation?.

Publications

Segregation Lag in Polyploid Cells of the Pathogen Genus <i>Borrelia</i>: Implications for Antigenic Variation .

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

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Segregation Lag in Polyploid Cells of the Pathogen Genus <i>Borrelia</i>: Implications for Antigenic Variation .