Biology subjects

Zavadska, D.

Publications and source records attributed to Zavadska, D..

5 recordsLinked to original sources

bioRxiv2026

Inverse relationship between mitochondrial and non-coding nuclear DNA content in free-living kinetoplastids

The evolution of genome size and eukaryotic genome organisation has puzzled evolutionary biologists for decades. Are differences in DNA content and protein-coding capacity of eukaryotic genomes a result of natural selection, or neutral processes? If they were shaped by natural selection, which features might be connected with these differences: cell volume, ecological strategy, availability of nutrients, etc.? Kinetoplastids are protists with compact nuclear genomes that almost entirely lack introns, but whose mitochondrial DNA content (kDNA) can rival that of their nuclei. We hypothesised that the reduction in non-protein coding nuclear DNA content during the evolution of kinetoplastids is connected with an increase in kDNA content: species with larger fractions of total cellular DNA that is allocated to kDNA will have concomitantly smaller fractions of non-coding DNA in the nuclear genome. We developed a framework for estimation of DNA content in both the mitochondria and nuclei from quantitative fluorescence microscopy data, and inferred the fraction of non-coding DNA in nuclear genomes based on the combination of transcriptomic and fluorescence imaging data. Across 10 genetically distant isolates from diverse free-living kinetoplastid lineages, there is indeed a trend towards a lower proportion of non-protein-coding nuclear DNA when kDNA proportion is higher relative to the total DNA in the cell. This observation is consistent with the hypothesis that in free-living kinetoplastids, mitochondrial and nuclear genomes might co-evolve in terms of their DNA content. This finding raises the possibility that natural selection acts on genome size evolution in kinetoplastids, and contributes evidence and methodology to address this question more broadly in eukaryotes.

evolutionary biology↗

bioRxiv2025

Phylogenomics of free-living neobodonids reveals they are a paraphyletic group from which all other metakinetoplastids are descended

Kinetoplastea is a major taxon of microbial eukaryotes that includes the well-known trypanosomatid parasites, species of which cause diseases in humans, animals and plants. Free-living kinetoplastids are greatly understudied compared to their parasitic relatives, but are ecologically important microbivores, and collectively comprise the great majority of kinetoplastid diversity. For two decades kinetoplastids have been divided into prokinetoplastids and metakinetoplastids, with the latter further split into four orders, the most diverse of which is Neobodonida. However, the position of the root of the metakinetoplastids and whether neobodonids are a clade has remained unclear due to very limited multi-gene data from free-living kinetoplastids, particularly neobodonids. Here, we present transcriptomic data for eleven newly or recently cultivated free-living neobodonid kinetoplastids. Phylogenomic analyses of a de novo generated data set of 444 inferred orthologs and 49 taxa robustly resolve the kinetoplastid tree, including the position of the root of metakinetoplastids. This divides metakinetoplastids such that Trypanosomatida, Eubodonida, Parabodonida, Allobodonidae (formerly neobodonid clade 1E) and neobodonid clade 1D fall on one side, while neobodonid clades Nd6, 1B (Rhynchomonadidae) and 1C fall on the other. Neobodonids are thus inferred to be a paraphyletic group from which all other metakinetoplastids descend. This analysis is the most thorough examination of metakinetoplastid phylogeny thus far, and forms a new basis for tracing the evolutionary history of the entire kinetoplastid group. Significance statementThis study provides transcriptomic data for 11 novel free-living kinetoplastid species, allowing the most accurate phylogeny of metakinetoplastids to date, revealing that neobodonids are paraphyletic and that eubodonids, parabodonids and trypanosomatids emerged within neobodonids. This new framework is essential for understanding the evolution of this major group of parasites and ecologically important free-living heterotrophs.

evolutionary biology↗

bioRxiv2025

The morphology and small subunit rDNA gene phylogeny of the novel goniomonad genus Ebisugoniomonas and two novel Poseidogoniomonas species

Goniomonads are heterotrophic representatives of Cryptista, sister lineage to the phototrophic Cryptists. Goniomonads are morphologically and genetically diverse, comprising nine genera described so far. Besides morphologically described genera, SSU rDNA sequencing data has revealed the existence of at least one more monophyletic genus-level lineage within goniomonads, as well as more novel species within the described genera. Furthermore, the diversity of SSU rDNA sequences within goniomonads is not fully investigated, and addition of novel sequences can be crucial for understanding the evolution and diversity of goniomonads and for providing a basis for taxonomic descriptions. The morphological data record available for goniomonads is relatively limited: many cellular features remain undescribed, or described only for a few isolates. In this study, we describe the new genus and species Ebisugoniomonas hispanica n. gen. n. sp., and two novel species within Poseidogoniomonas: P. posteriocircus n. sp. and P. zopfkaesiformis n. sp. We report a range of observations on the cellular features of goniomonads: periplast plate arrangement pattern and intracellular structures. We also update the SSU rDNA phylogeny of goniomonads by adding sequences from novel isolates and environmental DNA studies. Several sequences recovered from novel isolates and environmental DNA datasets likely represent highly divergent lineages of goniomonads in the SSU rDNA phylogeny.

microbiology↗

bioRxiv2023

On the relationship between protist metabarcoding and protist metagenome-assembled genomes

AO_SCPLOWBSTRACTC_SCPLOWThe two most commonly used approaches to study the composition of environmental protist communities are marker gene metabarcoding and whole genome analysis through metagenomics. Raw metabarcoding data are usually processed into Operational Taxonomic Units (OTUs) or amplicon sequence variants (ASVs) through clustering or denoising approaches, respectively. Analogous approaches have been developed to assemble metagenomic sequence reads into metagenome-assembled genomes (MAGs). Understanding the correspondence between the data produced by these two approaches can help to integrate information between the datasets and to explain how metabarcoding OTUs and MAGs are related with the underlying biological entities they are hypothesised to represent. Due to the nature of their construction, MAGs do not contain the most commonly used barcoding loci, meaning that sequence homology approaches cannot be used to match OTUs and MAGs. We made an attempt to match V9 metabarcoding OTUs from the 18S rRNA gene (V9 OTUs) and MAGs from the Tara Oceans expedition (2009-2013) based on the correspondence of their relative abundances across the same set of samples. We evaluated the performance of several methods for detecting correspondence between features in these two compositional datasets and developed a series of controls to filter artefacts of data structure and processing. After selecting the best-performing correspondence metrics, ranking the V9 OTU/MAG matches by their proportionality/correlation coefficients and applying a set of selection criteria, we identified candidate matches between V9 OTUs and MAGs. In a subset of cases, V9 OTUs and MAGs could be successfully matched with one another with a one-to-one correspondence, implying that they likely represent the same underlying biological entity. More generally, matches we observed could be classified into 4 scenarios: Scenario I - one V9 OTU matches more than one MAG; Scenario II - more than one V9 OTU matches more than one MAG; Scenario III - more than one V9 OTU matches one MAG; Scenario IV - one V9 OTU matches one MAG. These diverse scenarios for V9 OTU-MAG matches illustrate the complex nature of the OTU/MAG relationship. Notably, we found some instances in which different OTU-MAG matches from the same taxonomic group were not classified in the same scenario, with all four scenarios possible even within the same taxonomic group, illustrating that factors beyond taxonomic lineage influence the relationship between OTUs and MAGs. Overall, each scenario produces a different interpretation of V9 OTUs, MAGs and how they compare in terms of the genomic and ecological diversity that they represent.

bioinformatics↗

bioRxiv2022

Reduced mitochondria provide an essential function for the cytosolic methionine cycle

It has been long hypothesised that mitochondrial reduction is intrinsically related to the remodelling of Fe-S clusters assembly. Yet as our knowledge of divergent free-living protists broadens, so does the spectrum of variability within the range of mitochondrial-related organelles (MROs) fundamental functions. We resolved to high precision the MRO proteome of Paratrimastix pyriformis using Localisation of Organelle Proteins by Isotope Tagging (LOPIT) and demonstrate its role in the synthesis of folate derivates bearing one-carbon (1C) units, its link to the glycine cleavage system (GCS) and their only conceivable role as suppliers for the cytosolic methionine cycle, involved in recycling of S-adenosine methionine. This observation provides congruity to the presence of GCS in MROs of free-living anaerobes and its absence in endobionts, which typically lose the methionine cycle and, in the case of oxymonads, also mitochondria.

cell biology↗