Biology subjects

Slamovits, C. H.

Publications and source records attributed to Slamovits, C. H..

5 recordsLinked to original sources

bioRxiv2026

Proteomics reveals conserved features of histone biology in dinoflagellates

Current knowledge of DNA packaging in eukaryotic nuclei largely centers on its basic unit, the nucleosome. Multiple lineages have, however, diverged from this paradigm, most notably dinoflagellates. Among other molecular oddities, these enigmatic protists have enormous genomes, permanently condensed chromosomes and a foreign gene encoding Dinoflagellate Viral Nucleoprotein (DVNP), which is used for packing DNA. Some dinoflagellates also have Histone-like Proteins (HLPs) acquired from bacteria via lateral gene transfer. Dinoflagellates were long thought to lack histones entirely, but canonical histone genes have been identified by transcriptomics. Here, we performed proteomics on purified nuclei and confirmed the presence of all four core histone classes, along with variants, and DVNP in the dinoflagellates Oxyrrhis marina and Amphidinium carterae and HLPs in A. carterae. We also identified putative histone post-translational modifications found in canonical eukaryotes. Comparative genomics of dinoflagellates revealed histone-handling and modification machinery alongside an apparent reduction in, or diversification of, machinery responsible for replication-dependent nucleosome deposition (CAF-1), consistent with a predominantly transcription-associated role for nucleosomes. Furthermore, proteomics revealed modifications of DVNP and HLP, raising the possibility of machinery co-opting. These observations support a new model of a dinoflagellate chromatin that includes the localization of canonical nucleosomes to insulated chromatin territories (INTs).

evolutionary biology↗

bioRxiv2022

The development of intracytoplasmic membranes in alphaproteobacteria involves the conserved mitochondrial crista-developing Mic60 protein

Mitochondrial cristae expand the surface area of respiratory membranes and ultimately allow for the evolutionary scaling of respiration with cell volume across eukaryotes. The discovery of Mic60 homologs among alphaproteobacteria, the closest extant relatives of mitochondria, suggested that cristae might have evolved from bacterial intracytoplasmic membranes (ICMs). Here, we investigated the predicted structure and function of alphaproteobacterial Mic60, and a protein encoded by an adjacent gene Orf52, in two distantly related purple alphaproteobacteria, Rhodobacter sphaeroides and Rhodopseudomonas palustris. In addition, we assessed the potential physical interactors of Mic60 and Orf52 in R. sphaeroides. We show that the three -helices of mitochondrial Mic60s mitofilin domain, as well as its adjacent membrane-binding amphipathic helix, are present in alphaproteobacterial Mic60. The disruption of Mic60 and Orf52 caused photoheterotrophic growth defects, which are most severe under low light conditions, and both their disruption and overexpression led to enlarged ICMs in both studied alphaproteobacteria. We also found that alphaproteobacterial Mic60 physically interacts with BamA, the homolog of Sam50, one of the main physical interactors of eukaryotic Mic60. This interaction, responsible for making contact sites at mitochondrial envelopes, has been conserved in modern alphaproteobacteria despite more than a billion years of evolutionary divergence. Our results suggest a role for Mic60 in photosynthetic ICM development and contact site formation at alphaproteobacterial envelopes. Overall, we provide support for the hypothesis that mitochondrial cristae evolved from alphaproteobacterial ICMs, and therefore have improved our understanding of the nature of the mitochondrial ancestor.

evolutionary biology↗

bioRxiv2020

A comparative 'omics approach to candidate pathogenicity factor discovery in the brain-eating amoeba Naegleria fowleri

Of the 40 described Naegleria species, only N. fowleri can establish infection in humans, killing almost invariably within two weeks. In the brain, the amoeba performs piece-meal ingestion, or trogocytosis, of brain material causing massive inflammation. Conversely, its close relative Naegleria gruberi, which is used as a laboratory model organism, is non-pathogenic. The exact pathogenicity factors distinguishing N. fowleri from its harmless relatives are unclear. We have here taken an -omics approach to understanding N. fowleri biology and infection at the system level. We provide the first analysis of genomic diversity between strains, finding little conservation in synteny but high conservation in protein complement. We also demonstrate that the N. fowleri genome encodes a similarly complete cellular repertoire to that found in N. gruberi. Our comparative genomic analysis, together with a transcriptomic analysis of low versus high pathogenicity N. fowleri cultured in a mouse infection model, allowed us to construct a model of cellular systems involved in pathogenicity and furthermore provides ~500 novel candidate pathogenicity factors in this currently rare but highly fatal pathogen.

microbiology↗

bioRxiv2019

Comparative analyses of saprotrophy in Salisapilia sapeloensis and diverse plant pathogenic oomycetes reveal lifestyle-specific gene expression

Oomycetes include many well-studied, devastating plant pathogens. Across oomycete diversity, plant-infecting lineages are interspersed by non-pathogenic ones. Unfortunately, our understanding of the evolution of lifestyle switches is hampered by a scarcity of data on the molecular biology of saprotrophic oomycetes, ecologically important primary colonizers of dead tissue that can serve as informative reference points for understanding the evolution of pathogens. Here, we established Salisapilia sapeloensis growing on axenic litter as a tractable system for the study of saprotrophic oomycetes. We generated multiple transcriptomes from S. sapeloensis and compared them to (a) 22 oomycete genomes and (b) the transcriptomes of eight pathogenic oomycetes grown under 13 conditions (three pathogenic lifestyles, six hosts/substrates, and four tissues). From these analyses we obtained a global perspective on the gene expression signatures of oomycete lifestyles. Our data reveal that oomycete saprotrophs and pathogens use generally similar molecular mechanisms for colonization, but exhibit distinct expression patterns. We identify S. sapeloensis specific array and expression of carbohydrate-active enzymes and regulatory differences in pathogenicity-associated factors, including the virulence factor EpiC2B. Further, S. sapeloensis was found to express only a small repertoire of effector genes. In conclusion, our analyses reveal lifestyle-specific gene regulatory signatures and suggest that, in addition to variation in gene content, shifts in gene regulatory networks might underpin the evolution of oomycete lifestyles.

microbiology↗

bioRxiv2018

An updated phylogeny of the Alphaproteobacteria reveals that the Rickettsiales and Holosporales have independent origins

The Alphaproteobacteria is an extraordinarily diverse and ancient group of bacteria. Previous attempts to infer its deep phylogeny have been plagued with methodological artefacts. To overcome this, we analyzed a dataset of 200 single-copy and conserved genes and employed diverse strategies to reduce compositional artefacts. Such strategies include using novel dataset-specific profile mixture models and recoding schemes, and removing sites, genes and taxa that are compositionally biased. We show that the Rickettsiales and Holosporales (both groups of intracellular parasites of eukaryotes) are not sisters to each other, but instead, the Holosporales has a derived position within the Rhodospirillales. Furthermore, we find that the Rhodospirillales might be paraphyletic and that the Geminicoccaceae could be sister to all ancestrally free-living alphaproteobacteria. Our robust phylogeny will serve as a framework for future studies that aim to place mitochondria, and novel environmental diversity, within the Alphaproteobacteria.

evolutionary biology↗