Biology subjects

Potekhin, A.

Publications and source records attributed to Potekhin, A..

3 recordsLinked to original sources

bioRxiv2025

The tiny germline chromosomes of Paramecium aurelia have anexceptionally high recombination rate and are capped by a new class of Helitrons

BackgroundParamecia belong to the ciliate phylum of unicellular eukaryotes characterized by nuclear dimorphism. A diploid germline micronucleus (MIC) transmits genetic information across sexual generations. A polyploid transcriptionally active somatic macronucleus (MAC) develops at each sexual generation from a copy of the MIC through programmed DNA elimination (PDE) of > 30% of germline DNA. PDE requires the domesticated PiggyMac (Pgm) transposase. Assembly of Paramecium germline genomes has presented an enormous challenge owing to the difficulty of MIC isolation. ResultsWe report chromosome-scale short-read MIC assemblies for 7 species from the P. aurelia species complex. We discovered a novel clade of Helitrons, with 9-10 kb transposase ORFs under purifying selection, that have remained active in all P. aurelia lineages. A long-read assembly for P. tetraurelia together with a genetic linkage map provided a nearly telomere-to-telomere assembly. Conclusions.The genome consists of tiny (300 kb - 1.2 Mb) and numerous ([~]160) germline chromosomes with the highest recombination rate ever reported for a eukaryote (420 cM/Mb). The ends of the chromosomes consist of Helitrons inserted in telomeric C4A2 repeats, forming a distinct genomic compartment that is eliminated very early during MAC development in a Pgm-independent manner.

genomics↗

bioRxiv2022

Host association and intracellularity evolved multiple times independently in the Rickettsiales

The order Rickettsiales (Alphaproteobacteria) encompasses multiple diverse lineages of host-associated bacteria, including pathogens, reproductive manipulators, and mutualists. In order to understand how intracellularity and host association originated in this order, and whether they are ancestral or convergently evolved characteristics, we built an unprecedentedly large and phylogenetically-balanced dataset that includes de novo sequenced genomes and an accurate selection of published genomic and metagenomic assemblies. We performed detailed functional reconstructions that clearly indicated "late" and parallel evolution of obligate host-association and intracellularity in different Rickettsiales lineages. According to the depicted scenario, multiple independent series of horizontal acquisitions of transporters led to the progressive loss of biosynthesis of nucleotides, amino acids and other metabolites, producing distinct conditions of host-dependence. Coherently, each clade experienced a different pattern of evolution of the ancestral arsenal of interaction apparatuses, including development of specialised effectors involved in the lineage-specific mechanisms of host cell adhesion/invasion and intracellularity.

microbiology↗

bioRxiv2018

The extracellular association of the bacterium \"Candidatus Deianiraea vastatrix\" with the ciliate Paramecium suggests an alternative scenario for the evolution of Rickettsiales

Rickettsiales are a lineage of obligatorily intracellular Alphaproteobacteria, encompassing important human pathogens, manipulators of host reproduction, and mutualists. Here we report the discovery of a novel Rickettsiales bacterium associated with Paramecium, displaying a unique extracellular lifestyle, including the ability to replicate outside host cells. Genomic analyses show that the bacterium possesses a higher capability to synthesize amino acids, compared to all investigated Rickettsiales. Considering these observations, phylogenetic and phylogenomic reconstructions, and re-evaluating the different means of interaction of Rickettsiales bacteria with eukaryotic cells, we propose an alternative scenario for the evolution of intracellularity in Rickettsiales. According to our reconstruction, the Rickettsiales ancestor would have been an extracellular and metabolically versatile bacterium, while obligate intracellularity and genome reduction would have evolved later in parallel and independently in different sub-lineages. The proposed new scenario could impact on the open debate on the lifestyle of the last common ancestor of mitochondria within Alphaproteobacteria.

evolutionary biology↗