Aug 2026· Molecular Phylogenetics and Evolution· Vol 225, pp.
108726
· 0 citations· 73 references
Medicine
TL;DR
The results support algae-to-host HGT in P. bursaria and suggest that some transferred genes may contribute to metabolic integration during endosymbiosis.
Abstract
Paramecium bursaria maintains a stable endosymbiosis with green algae, yet the evolutionary consequences of this association remain unclear. Here, we screened the host genome for algal-derived horizontally transferred genes (HTGs) using a lineage-aware workflow designed to detect horizontal gene transfer (HGT) between two defined lineages. We identified 16 candidate HTGs, including four putative newly transferred genes and 12 homologous transferred genes, most of which were functionally associated with redox homeostasis and metabolism. Five HTGs showed symbiosis-dependent expression. RNAi knockdown of GH32s and SATs reduced host proliferation, total cell area, and motility, while GH32s knockdown also reduced endosymbiont load. Duplication patterns suggest that most transfers may have occurred after the P. bursaria lineage diverged from the sampled Paramecium species but before its lineage-specific whole-genome duplication (WGD). The HTGs also showed host-associated shifts in GC content and gene length, while representative HTGs retained conserved domains and functional motifs. Together, our results support algae-to-host HGT in P. bursaria and suggest that some transferred genes may contribute to metabolic integration during endosymbiosis.
Comparisons of complete mitochondrial genomes of the parasites and their hosts found that closely related species evolved dramatically different genome architectures through distinct mechanisms: one lineage accumulated large amounts of host-derived DNA, whereas another expanded through the proliferation of repetitive sequences with limited contribution from foreign DNA.
LF Ceriotti, L. Gatica-Soria, W. Tulle et al.· bioRxiv· 0 citations
Abstract Horizontal gene transfer (HGT) can accelerate plant adaptation, but the evolutionary fate of newly acquired nuclear genes is often unclear. Here, we analyzed a papain‐like cysteine peptidase horizontally transferred from Panicoideae to wild Hordeum (Poaceae). Using chromosome‐level assemblies of 21 diploid Hordeum species, we assessed presence/absence, copy‐number variation, coding diversity, selection, predicted protein functionality, and expression. To infer donor relationships, we screened 77 Panicoideae accessions (48 species, 20 genera) by polymerase chain reaction and sequenced positive amplicons with Nanopore. The transferred locus, likely acquired as part of a larger panicoid DNA segment, is retained across Hordeum sect. Stenostachys but shows strong post‐transfer diversification, with 1–8 copies per species, extensive transposable‐element insertions, and numerous coding‐sequence variants. Close homologs in Panicoideae were rare and restricted to Panicum and Paspalum; gene trees identified Panicum bergii as the closest sampled relative. Selection analyses indicated heterogeneous constraints and episodic positive selection in some Hordeum lineages. Only a minority of copies retained an intact catalytic triad, whereas most were predicted to be pseudopeptidases. Transcripts were detected across species and tissues. These results indicate that an HGT‐derived DNA block can persist, amplify, and diversify in recipient genomes, generating raw material for later functional evolution.
V. Mahelka, P. Caklová, R. Čegan et al.· The Plant Genome· 0 citations
Although numerous studies have documented horizontal gene transfer (HGT) from bacteria into insect genomes, they have been heavily biased toward the endosymbiont Wolbachia. In contrast, comparatively few studies have examined HGT from other symbionts and insect-associated bacteria. Moreover, research on these systems has primarily focused on transferred genes that retain function in the insect host, contributing to metabolism, symbiosis, detoxification, or host adaptation. Consequently, relatively few empirical systems have been available to investigate the persistence, degradation, diversification, and vertical inheritance of apparently non-functional HGT-derived sequences over macroevolutionary timescales. The widespread occurrence of putatively Arsenophonus-derived sequences across Cimicidae therefore provides a rare opportunity to extend these investigations beyond the Wolbachia model and to examine the long-term evolutionary fate of non-functional HGT-derived DNA across tens of millions of years of host diversification. We show that Arsenophonus-derived HGTs have multiple independent origins across Cimicidae but that one major HGT lineage has persisted through diversification of the subfamily Cimicinae for at least 50 million years. Phylogenetic and compositional analyses indicate that an ancestral Arsenophonus-derived genomic region has undergone progressive fragmentation, leaving numerous dispersed, apparently non-functional remnants while preserving a clear evolutionary signature. These results extend the study of bacterial HGT beyond the Wolbachia model and demonstrate that non-functional symbiont-derived DNA can persist over macroevolutionary timescales.
Shruti Gupta, J. Martinů, O. Balvín et al.· bioRxiv· 0 citations
Abstract Endosymbiosis is a major driver of evolutionary innovation and underpins the function of diverse ecosystems. The origins and evolution of endosymbiosis are challenging to study experimentally due to the short-lived culturability of many microbial strains derived from endosymbiotic interactions. The facultative endosymbiosis between the ciliate, Paramecium bursaria, and the green alga, Micractinium conductrix (Chlorellaceae, Trebouxiophyceae), is ecologically widespread and has emerged as a powerful lab-tractable model system. This endosymbiosis is founded upon a reciprocal nutrient exchange, but each of the species can be cultured independently enabling quantification of symbiotic fitness effects, new partnerships to be generated in the lab, and co-associations to be subject to experimental evolution. To date, evolve-and-resequence approaches have been limited due to a lack of high-quality genome assemblies enabling gene variants to be identified. Here, we report a near telomere-to-telomere genome assembly for M. conductrix 186b, using a range of sequencing technologies. Comparative analysis shows that this is one of the most complete Chlorellaceae algal genome assemblies available to date. To aid accurate gene calling and annotation, we conducted both RNAseq and Iso-Seq transcriptome sequencing experiments. Collectively, these ‘omics datasets will facilitate: (i) comparative genomics studies of endosymbiont evolution, (ii) evolve-and-resequence experiments, (iii) genome-scale metabolic modeling studies, and (iv) identification of targets for genetic modification experiments and biotechnological applications.
G. Leonard, Irma Vitonytė, Fiona R. Savory et al.· Genome Biology and Evolution· 0 citations
It is demonstrated that homologous recombination, genome plasticity, and lineage-specific diversification are major drivers of adaptation, ecological fitness, and pathogenic evolution in this emerging phytopathogen P. jejuense across diverse hosts and geographic regions.
Dario Arizala, S. Dobhal, Gamze Boluk et al.· bioRxiv· 0 citations
This study provides genome- and spatially resolved views of dominant SCB in holothurians and offers evolutionary insights into host-interface diversification in the deep-sea holothurian body wall.
