Biology subjects

Novak Vanclova, A. M. G.

Publications and source records attributed to Novak Vanclova, A. M. G..

4 recordsLinked to original sources

bioRxiv2026

Characterisation of the new microalgal protein xATPA related to the F-type ATP synthase α subunit, from the ecosystem to the molecule

Microalgal metabolism relies on their chloroplasts, and involves both nucleus and plastidial-encoded proteins of various evolutionary origins. The plastidial ATP synthase complex is a key player in photosynthesis, and has been extensively studied in plants. However, our knowledge in other photosynthetic eukaryotes remains limited, despite their importance in marine environments. Here, we report the characterisation of a novel homologue of the F-type ATP synthase alpha subunit, hereby named xATPA, widespread in microalgae but absent from other photosynthetic organisms. Comparisons of xATPA sequences and predicted structures revealed a specific feature, the bump domain, and highlighted the absence of an ATP-binding site. We assessed xATPA prevalence in microalgae in the global ocean using environmental data from Tara Oceans, with a particular focus on diatoms, and demonstrate that its expression is associated with polar summer conditions. Using a reverse genetic approach in the model diatom Phaeodactylum tricornutum, we show that xATPAPt has a plastidial localisation, and that xATPA KO mutants exhibit growth deficiencies in a combination of low temperature, low salinity and constant light, consistent with environmental analysis. Surprisingly, both RNAseq and physiological assays suggest that xATPA is not involved in ATP synthase functions. On the other hand, xATPA interacts with other F1 ATP synthase subunits in vitro, which we suggest forms transient unassembled complexes. This study hence represents a comprehensive analysis of a novel protein from the environment to the lab, and reveals a new player in the plastidial physiology of eukaryotic microalgae.

plant biology↗

bioRxiv2025

Eukaryotic recombinases duplicated after divergence from known asgardarchaeal RadA: implications for the evolution of sex during eukaryogenesis

The origin of meiotic sex was a key milestone in the evolution of the eukaryotic cell. The DNA recombinases Rad51 and DMC1 have been used previously to trace the timing and origins of the meiotic machinery, and warrant revisiting in the face of the recent increased diversity of reported asgardarchaeal taxa. Here we perform comparative genomics and phylogenetic analyses of RadA protein sequences from a broad sampling of eukaryotic and archaeal taxa. We show that even with increased and new sampling, the eukaryotic Rad51 and DMC1 proteins still resolve separately from any archaeal RadA sequences. Taking into account recent evolutionary cell biological discoveries, our data are most consistent with a scenario whereby the asgardarchaeal host cell was evolving cytoskeletal and membrane-protein machinery that was later incorporated into eukaryotic endomembrane systems following the acquisition of mitochondria and the evolution of sex.

evolutionary biology↗

bioRxiv2022

Divergent and diversified proteome content across a serially acquired plastid lineage

Dinoflagellates are a diverse group of ecologically significant micro-eukaryotes, prone to the loss and replacement of their plastids via serial endosymbiosis. One such replacement took place in the ancestors of the Kareniaceae, which harbor haptophyte-derived plastids containing the pigment fucoxanthin, instead of the ancestral peridinin dinoflagellate plastid. The metabolic functions of the fucoxanthin plastid are performed by a diverse range of nucleus-encoded and plastid-targeted proteins, which may originate from the haptophyte ancestor of the fucoxanthin plastid, the peridinin-containing ancestor of the dinoflagellate host, and/or from lateral gene transfers. However, the evolutionary composition of fucoxanthin plastid proteomes across the diversity of kareniacean dinoflagellates remains poorly understood. Here, we determine the total composition of the plastid proteomes of seven distantly-related kareniacean dinoflagellates, including newly-sequenced members of three genera (Karenia, Karlodinium, and Takayama). Using a custom plastid-targeting predictor, automatic single-gene tree building and phylogenetic sorting of plastid-targeted proteins, we project relatively limited (~10%) and functionally distinctive contributions of the haptophyte endosymbiont to the fucoxanthin plastid proteome, in comparison to plastid-targeted proteins of dinoflagellate host origin. Considering a concatenated multigene phylogeny of haptophyte-derived plastid proteins, we show that the haptophyte order Chrysochromulinales is the closest living relative of the fucoxanthin plastid donor. We additionally perform detailed analyses of the N-terminal targeting sequences of kareniacean plastid signal peptides, reporting a surprisingly high sequence conservation. Finally, considering planetary-scale distributions of key kareniacean genera and haptophyte orders from Tara Oceans, we suggest ecological and mechanistic factors accompanying the endosymbiotic acquisition of the fucoxanthin plastid.

microbiology↗

bioRxiv2018

Peculiar features of the plastids of the colourless alga Euglena longa and photosynthetic euglenophytes unveiled by transcriptome analyses

Background: Euglenophytes are an interesting algal group that emerged within the ancestrally plastid-lacking Euglenozoa phylum by acquiring a plastid from a green algal donor. However, the knowledge of euglenophyte plastid biology and evolution is highly incomplete, partly because euglenophytes have so far been little studied on a genome- and transcriptome-wide scale. Transcriptome data from only a single species, Euglena gracilis, have been exploited to functional insights, but aspects of the plastid biology have been largely neglected.\n\nResults: To expand the resources for studying euglenophyte biology and to improve our knowledge of the euglenophyte plastid function and evolution, we sequenced and analysed the transcriptome of the non-photosynthetic species Euglena longa. The transcriptomic data confirmed the absence of genes for the photosynthetic machinery in this species, but provided a number of candidate plastid-localized proteins bearing the same type of N-terminal bipartite topogenic signals (BTSs) as known from the photosynthetic species E. gracilis. Further comparative analyses using transcriptome assemblies available for E. gracilis and two additional photosynthetic euglenophytes of the genus Eutreptiella enabled us to unveil several salient aspects of the basic plastid infrastructure in euglenophytes. First, a number of plastidial proteins seem to reach the organelle as C-terminal translational fusions with other BTS-bearing proteins. Second, the conventional eubacteria-derived plastidial ribosomal protein L24 is missing and seems to have been replaced by very different homologs of the archaeo-eukaryotic origin. Third, no homologs of any key component of the TOC/TIC system (translocon of the outer/inner chloroplast membrane) and the plastid division apparatus are discernible in euglenophytes, and the machinery for intraplastidial protein targeting has been simplified by the loss of the cpSRP/cpFtsY system and the SEC2 translocon. Lastly, euglenophytes proved to encode a plastid-targeted homolog of the termination factor Rho horizontally acquired from a Lambdaproteobacteria-related donor, suggesting an unprecedented modification of the transcription mechanism in their plastid.\n\nConclusions: Our study suggests that the euglenophyte plastid has been substantially remodelled comparted to its green algal progenitor by both loss of original and acquisition of novel molecular components, making it a particularly interesting subject for further studies.

evolutionary biology↗